Lean mixture, screws 6 turns out already

Well I have searched and not yet found anything that sounds quite like whats happening to my XJ-it's running lean (white as powder plugs) and I noticed this because my idle lowered (after being steady at 1200 for ~300miles) and I could hear a little sputter sound in the pipes all of a sudden which was new after those 300 miles (3 weeks time).
I am fairly new to the XJ world and my previous bike was a Nighthawk, and all I had to do was change the fluids. I have to admit I am enjoying working on the XJ and really love it so I need help to keep from killing it.
Background: purchased (1981 XJ550 Maxim-28,000mi.) 6 weeks ago from the po who had it for a little more than 500 miles. He said the owner before him had adjusted the valves, now 800 miles ago (I know I need to double check this) . The po replaced the rear brake and cleaned/bench synched the carbs. When I got the bike from him it wouldn't start easily and took a long time to warm up (thats common). He thought it might be the stator/battery causing the problem, but I don't think it was; I charged the battery and it shows 14.47v at 5000rpm. He was using reg unleaded (might have ethanol) and the bike needed a little TLC (mostly just cleaning/oil chang). I changed the oil (20w50 racing oil), put in quality gas and a little sea foam. After changing the plugs and the oil again after the sputter showed up, the bike now starts really easy even without much choke. It has a very noisy clutch (at idle), but from what I've read I probably shouldn't worry about that too much. The HI-VO chain got much quieter with the second oil change.
Back to the issue at hand. All four plugs are sparking fine, there are no vacuum leaks, I installed an in-line fuel filter. The bike idles fine now after I adjusted the knob (albeit noisily at 1150-1250 rpm) and seems to have plenty of power (maybe just a barely noticeable power drop between 8000-9000rpm). When I pulled the tank and checked the pilot screws they were (#1-6,#2-6.25,#3-5.5,#4-6.25) turns out already! The bike has a K&N oiled air filter which had a slight gap at the top and bottom where it meets the air-box, so I sealed the gap up with some silicone gasket-no help) Everything else is stock. I don't have a YICS tool or a tool for vacuum synching the carbs, and because I am a broke full time student (and I spent the $ on this bike to try and save gas money over my 6000lb truck.) I can't really drop a lot of $$$ into my XJ right now, but I am planning on checking the compression tomorrow (should've done that first eh? But I'll bet it's fine because this little 550 pulls as hard as my CB650 did up to 80mph at least). What am I missing that could cause it to run so lean? is there any inexpensive way for me to fix this? Can I synch my carbs for less than $50? Shouldn't the screws being out so far make it rich?
I really need to commute with this baby and don't want her to die, so I'm not riding tomorrow after discovering this super leaness (I checked the plugs after a 30mi commute and then did a plug chop (white, white, white and dry!) The bike is in incredibly good condition otherwise for a 1981 Yama, although there are other less pressing projects I'm sure I'll need help with. Thanks for any information.

 

I got $5 that says the PO's PO lied and you'd better have a peek at the valve clearances right away. Right away, as in immediately.

AFTER you pitch that K&N and put a stock air filter in it. Then you'll probably need to run the mixture screws back in;

UNLESS PO lied about the carbs too in which case you've got some work to do. Since he admitted to having the carbs apart, I would now be highly suspicious of the float levels.

Yes, you can sync your carbs for under $50. YICS can be blocked with an old t-shirt twisted into a rope and soaked in motor oil; and you can build a "comparative manometer" from a couple of plastic baby bottles and some clear vnyl tubing, or just a long piece (6') of vinyl tubing, a yardstick and a few zip-ties.

AFTER you check the valve clearances, verify the float levels and be sure the carbs actually ARE clean.

FORGET everything PO told you; he believed the lies the guy before him told and he just passed them along. With a little "editorial license" taken along the way, apparently.

RE: OIL-- you said "20W50 Racing Oil." Motorcycle oil, right? As in motorcycle specific, NOT automotive oil?

Now, I hate to pee in your cornflakes, but how old are the TIRES? You said you're commuting with the bike; please check the date codes on the tires. If you can't FIND any date codes, then they're really old. Anything over 6 years is dangerous.

You also need to check the date code on the front brake hose. Originals had a recommended lifespan of 4 years.

If you're gonna commute on this bike it has to stop as good as it goes.

And one more thing: Don't wait until winter to adjust the cam chain; it takes all of maybe 10 minutes and doesn't require anything more special than a deepwell socket. Do it when you check the valve clearances, since you'll have the ignition cover off anyway. Soon.

 

MercuryMan, from your writeup I can tell that you are mechanically savvy. Good. Heed Fitz's advice, check valves, clean/sync carbs etc...and I STRONGLY encourage going back to stock filter. Ask more questions here and you'll get her running. Maybe some kind person in AR will lend a hand.

 

Opening the Pilot Mixture Screws to 6 Turns out renders them susceptible to being lost.
Beyond 5 Turns they have reached Wide Open and don't get "Wide-opener"

Breakdown at High rpm's could mean that the Diaphragm Pistons are not functioning properly and their Bores need to be scrubbed and refinished.

Or, ...

The Emulsion Tubes (Center Nozzles) have clogged Air Metering Ports which prevents the Main Jet Fuel Supply from being drawn-up into the Intake Stream in sufficient quantity -- and/or -- the Fuel drawn-up from the Main Jet is not being sufficiently atomized and is being introduced to the Combustion Chamber in droplet form ... unable to provide a highly explosive mixture and robbing the bike of the higher power it could make if the fuel was better mixed with the air.

 

Thanks Fitz and Rick your knowledge and help are most appreciated. Here's what's new and answers to your questions Fitz.

Just checked the compression and the numbers are not too bad: #1-133, #2-125, #3-126, #4-135
Curious that the #3, #4 plug showed some signs of slightly richer running after warming up to check compression, of course that was mostly on choke-the first 3 minutes of 6 (& Prime) for just 1.5 easy miles around the hood. But #1 and #2 are still showing lean (I will try to post the pic if I can get it to work).

I know you are totally right about the valves Fitz. I can't trust the po's po because there's no way to be sure. I have a fair amount of faith he did a good job on the carbs-mainly because this XJ was the fifth bike in his garage, he had built a bobber, he likes to work on bikes in his garage and he just the type to do it right.

Sorry about the noob questions I'm about to ask:
Just so I'm straight on the valves: to check them all I need is a feeler gauge and the tools to get the cover off right? (and read the write up in here about the specifics) Then to fix them if they are "out" I need that special tool, the proper shims (from chart), and a new gasket yes (can/should one use an rtv gasket)? Is that all I will need (besides time and patience)? Is Chacal the best one to get these supplies from and if so how do I pay/order from him?

I am searching for an OEM air filter now as well.

Answers to your questions Fitz:

Royal Purple 20w50 (not MC specific-guessing I should change it?)
Tire codes Front: "NA7M3407" (34th week of 2007?) I am changing it ASAP with either with a Dunlop D404 or a Shinko 733. Rear: "NA7M4308" (43rd week of 2008) it still has pretty good tread
Front Brake Hoses (bad news): "DOT MRCC 4/81" guess that makes them 30 years old (Yikes!) question here: my front brake does work pretty good, but I can't adjust the free play (1.5inch) because the screw is already adjusted all the way in. Does this mean my master is shot? Those old cables maybe? But it does brake about an 8 out 10 right now. I know this is critical though because trying to stop with just the rear is a carnival ride I don't want to take at 70mph. Where is the best place to get replacement hoses for this? Is stainless worth the $?

On the cam chain (sorry this is a rambling thread)-do I need a new gasket for the ignition cover or would high temp rtv work?

Thanks again for all your help. You have convinced me that I've just got to do it the RIGHT way and keep from destroying this iconic/classic moto-even if it means driving my guzzler again and spending 5 times as much on gas for a week or so (dang!)

Oh and did I mention that it's Sunny, 82 degrees, crystal blue sky, and almost no wind outside today and for days to come - arrrrrgh!

If this works here is the plugs and after that a picture of the Maximator.

http://i1091.photobucket.com/albums/i39 ... plugs1.jpg
http://i1091.photobucket.com/albums/i39 ... /Maxim.jpg

 

Damn, dude. Lots of typing but you're on the right track so I'm not gonna not;

Re: Valves. Correct; except replace the gasket and donuts once, now, and be done with it. It WILL leak otherwise. It can then be re-used multiple times after that.

YES, chacal is the best supplier for all of this stuff and the only things you will find cheaper are crap repro parts that will drive you crazy when they don't work right. Look in my gallery. I rode the black bike to work and back, 120+ miles today, and will again tomorrow and the next day if this gorgeous weather holds (sorry.) I've got two 550s, and I couldn't do this without XJ4Ever, and about everyone else here will agree with me.

He's got both OEM and OE-equivalent aftermarket air filters, too.

You need to run motorcycle-specific oil. Automotive oils that meet current specs contain friction modifiers that can play havoc with your clutch and starter clutch. Real motorcyle oils now have our own spec: JASO. You're familiar with auto oils and the "API" numbers. Motorcycle oils only meet about SG or so; but they exceed the new JASO standards. Castrol 4T is readily available; if you want a synthetic I'm running Castrol ACT>Evo X-tra 4T 20W40 in my '83.

Re: brakes. Yes, those are scary. And yes, stainless lines are well worth the upgrade; I have them on both of my 550s. I have low bars on my Secas, so I got custom length lines from chacal. Have you checked the rear yet? They delaminate and lock up when you least expect it: http://xjbikes.com/Forums/viewtopic/t=15874.html and a member just found this: http://xjbikes.com/Forums/viewtopic/t=34257.html Unless this reliable individual you bought this bike from showed you receipts, please check.

As for the rest of the brakes, you are going to need to rebuild the caliper and master cylinder. Those rubber seals were supposed to last TWO years. If you don't, you'll start experiencing brake drag soon after putting the bike back on the road. Neither procedure is terribly difficult nor expensive; just a PIA.

Get a new gasket for the ignition cover; the old one may come off intact or crumble into bits. Glue the new one to the cover with gasket sealer, and lightly oil the other side. LIGHTLY. Or smear it with silicone grease (your new best buddy, BTW.) Then as with the other gaskets, it should be re-usable next time.

Just plan to replace any 30 year old gasket the first time you disturb it; a lot of them were designed to be multi-use but the years took their toll.

You won't use a lot of RTV if you do this right. Done right, the bike won't leak.

You've got a chain drive bike now; are you familiar with how to properly check the chain and sprockets for wear? If not, say so and we'll get you going in the right direction.

Get yourself a BOOK. The Clymer is fine, the factory book better (for an experienced mechanic) and a combination of the two is the best.

You found the valve adjustment how-to, right? Lots of other good stuff in "FAQ Suggestions."

ASK questions; we won't make fun of you (just yet.)

 

Oh, and those are nice compression numbers. You're not too late on the valves, and I'll bet #2 and #3 will get even better once you bring the valves into spec.

 

Update: and in need of advice.

Got the stock air filter-after install bike would not idle. Took pilot screws back to 2.5 turns out. Still no idle, but running much richer (could see a tiny bit of smoke and 3/4 plugs not white, #2 still mostly white, #4 def. rich. No adjustments seemed to work for it. Strange though after this #1,#2 cylinder stopped getting real hot and could tell bike was really running on only 2 cylinders (3&4). Plugs not fouled, spark good...don't know. Going to borrow a friends colortune friday hopefully.

Got verification that po cleaned, bench synched, dry set floats, wet set floats, & colortuned. He didn't detail outside of carbs (but they look decent) or vacuum synch (no tools).

Warning real noob and possibly mechanically challenged questions next!

So I am on the quest now. Don't have all the parts I need yet, but started process. You know THE PROCESS. Valves first. then...So I am badly needing advice (since this is my first valve adjustment.)

I will include pictures of the below questions so you can evaluate.
After I got the cover off (ugh!)it was snug on there, the area around the lobes and shims is full of oil (normal?) Didn't see that in Fitz's pictures. Do I need to mop it up some before I check clearances? The gasket on the cover looks pretty new, can I reuse it? I have a new one. What about the donuts do they still look good?





Should I just quit college now so I can focus on this project full-time.
Seriously is it ok for the petcock vacuum line to run off the #2 Carb? Oh and finally does anyone have any ideas about what happened to my two not hot cylinders? After just an air filter change and pilot adjustment?

 

-The oil is fine, I mopped up bunch for the pictorial so people could see better.

-You CAN re-use the gasket, as long as it isn't brittle anywhere and still nice and pliable. Be sure to clean both it and the cover channels thoroughly, and follow the procedure of "glueing" it to the cover and greasing the underside, EXCEPT stop short with the grease and add a small bead of RTV right in the "corners" where the half-moons meet the gasket.

-Those donuts look ok, but they also look pretty mashed. Compare them to the pic in the article of the new ones; you're looking at the "shoulder" height. You can try re-using them; if the cover leaks you'll need to replace.

-The petcock vacuum line DOES come off the #2 manifold on the 550s. It comes off #3 on the bigger bikes.

-I suspect that even though PO had the carbs apart, he may not have gotten them fully cleaned. The books tell you to NEVER TOUCH the pilot mixture screws; however if they weren't pulled and that passage cleaned, their o-rings replaced, etc., you're going to have issues. The other thing that gets overlooked, carb-wise, is the enrichment wells, because they're IN the float bowls. If you don't know what you're looking at, you'd never know you have a problem. "Cleaning" Mikunis is one thing; doing it right is another. I would definitely have another peek at the carbs yourself. Here's a Mikuni completely broken down except for the throttle shaft/butterfly: http://xjbikes.com/Forums/viewtopic/t=31061.html I don't think he got the carbs 100%.

 

If adjusting the Pilot Mixture Screws does nothing to the performance, ... that fact is an indicator that the Pilot SYSTEM is not functioning properly.

Very often its just clogged Pilot FUEL Jets.
But, the Passages between the Fuel Bowl and the Top-end need to be flushed-out, too.

You are at an impasse.
Without thoroughly Cleaned Carbs supplying Fuel for Pilot, Enrichment and Wide-Open conditions, ... you can't get the Bike to run right.

You say the outsides of the Carbs dont look too cleaned and spiffy.

I would consider that a sure sign that that any claims made to you about those Carbs being Cleaned well enough to support fine-tuning are grossly exaggerated.

 

Fitz your were right, and now I must bow before the masters of the XJ's. I did need to check my valve clearances. Step 1 of valves complete here are the numbers:

#1 #2 #3 #4
E-.127mm E-.178mm E-.178mm E-.102mm
I-.102mm I-.102mm I-.102mm I-.102mm

If I found the right specs, then I am too tight (by a little) on all 4 intakes and too tight by a lot on #1 exhaust, and by a mile on #4 exhaust. Is this right? I am waiting on the shim tool to be able to pull shims (not comfortable doing it any other way).

It looks like since shims only go in .05mm increments that I will be at .152mm on all 4 intakes, .177mm on #1 E, and .202mm on #4 E. Is this ok?

Fitz do you think the carbs not being clean enough could account for #1 & #2 going from working and hot (with the K&N filter) to only warm and seemingly not combusting after I put in the stock filter and tried to make it run richer? The bike will die when I pull any of the plug wires, but I can touch the pipes on 1&2.

I took a picture of the #2 carb intake as seen through the air-box since it can be seen.


Does anything look strange or bad in this picture? I know it's not much to go on, but it didn't look exactly like I expected it to. The limited stuff I can see does look clean.

Thanks again for helping me save this great bike. I will keep you posted once I get tools, parts and go further.

 

You should really pop the top and bottom off to check everything, however I will say that looks DAMN CLEAN.

 

Hey, Boys!

THAT's is the WORST place to look to determine if the Carbs are Clean.
It' the INTAKE.
The GAS getting sucked into the Engine "Cleans" that view.

When you can't get a bike too respond to the PILOT MIX SCREWS being adjusted, ... there is NO GREATER CLUE to the Pilot FUEL Jet and Pilot AIR Passage needing to be: a) Cleaned, ... and b) Flushed.

Bikes can be Tuned with extremely Tight Valves.
Bikes can be Tuned with borderline Low Compression.

But, if the Carbs aren't able to deliver the critical mixtures of Fuel and Air required to run the bike, ... you twisting-out the Pilot Screws some more won't help.

Don't take anybodies word that the Carbs were just recently cleaned.

That lie is bigger than the one that begins: "Don't worry honey, ..."!!!

 

Truth. I once just about got a perfect idle on my '75 Honda CB450 with the choke on. Carbs were spotless.

About half of the questions on this site are about cleaning and tuning carbs. Take heed of that, clean and tune and you will be happy.

 

I'm not liking the looks of your main air jet. It looks like it's varnish plugged to me.



It's the little brass orifice in the lower right of your pic next to the slider piston. That'll give you all sorts of performance issues, and I know from experience that they're not as easy as you'd think to clean.

 

For starters, you're using an American gauge with metric equivalents; we really don't need to worry about that .002mm. The job is much easier with a "primarily metric" feeler gauge.

That being said, your math is correct and what you have outlined above is how I would proceed myself. Good job.

Re: your carbs. Everything you're describing points to the carbs not being cleaned properly to begin with. You can't tell anything by "peeking in" the intake side. Pull the rack; "field strip" them, and see how they look. REMOVE the pilot mixture screws, and inspect the tiny o-rings. Pop the emulsion tubes out, and check them for cleanliness inside and out, including all the tiny holes.

Check the enrichment wells in the float bowls; inspect the "beanie" screens; check the condition of the float valve seats.

I have a feeling somebody did a half-arsed job on the carbs.

 

Let's try to solve this: Below is a quote from PO in reference to what he did to the carbs <700 miles back.

"I stripped them completely and replaced everything that could wear
out. The shaft seals were so worn that they crumbled. I even used
welding tip cleaners in the smaller passages. Those carbs are as clean as they get without soda blasting. "

So I'm not saying it's not the carbs, but I really don't think it could be.

Also to summarizes the events:

Bike was a little reluctant to start (but did everytime) at first. Charged battery, put in Shell 91 octane/2oz SeaFoam, changed oil. Bike started fine (about 3minutes to warm up), and idled around 1200.

Rode it for ~300 miles over 3 week period, everything seemed fine except noisy clutch and HI-VO chain at idle. Gas mileage during this went 39(1st tank), 48(2nd), 51(3rd). Power also seemed really good comparable to my CB650.

Then after 10minutes of slow go (getting hot) idle dropped to 1000 and I could hear a little sputter in tail pipes. Checked plugs (white). Process to richen mixture started.

Sorry lots of questions here:
Could something have happened to the carbs in that amount of mileage/time? Varnishing or some kind of debris? If the carbs are good then what else would cause the drop in idle and the sputtering in the pipes, and now 1&2 to not be getting hot? Could the #1,#4 Evalves being tight be the reason. Could the carbs just be badly out of synch? More evidence-when it did get richer with the stock air filter the plugs were darkest to light in this order 4-3-1-2, with 4 looking maybe too rich, 3 perfect, 1 almost lean, 2 still lean-this is running at idle or with choke on (no plug chop).

If I pull a plug and it's arching more than 1" to the engine it's got to be good spark right? Is water in the fuel possible? Wouldn't 3&4 go down with 1&2 if that was the case?

 

ANYTHING is possible. However:

And I still do. Disregard what he SAID unless you watched him do it. Just because he knows the right things to say doesn't mean he actually did them. PO of one of my bikes claimed "carbs professionally cleaned and adjusted." He lied too.

Also, if he did use welding tip cleaners, he could have DAMAGED some of the jets or small passages.

I still think they're just not properly clean though, honest.

YOU need to have a look. Do it while you wait for your shims.

 

He could have cleaned them, but if there was any debris in the tank and there was not a filter installed on the fuel line then the carburators could have gotten fouled in the 300 miles like you describe. You definately want to add a fuel filter if it does not have one already. There is a write up for that in the forum FAQ Suggestions:
http://xjbikes.com/Forums/viewtopic/t=6352.html

 

Thanks Fitz and all. If I understand right, what you're saying is that I don't have proper fuel flowing (hence the leaness). It's likely due to clogged jets or dirty passages, and based on what Rick said it's almost certain that the pilot jets are clogged or have dirty passages, at least on 1&2 since turning them seemed to have no effect.

I did install an in-line fuel filter, but that was after the first 300 miles. I was curious about the appearance of the fuel in the line (it's a clear line). Is it supposed to be completely filled with fuel? There are air bubbles in the line and the filter only fills about 2/3, but I thought this was normal since it's not a pressurized feed and as long as fuel is going down it should be enough, right? The line comes off the petcock and drops at a slight angle to the filter which also tips downward then it turns (no kinks) and goes straight down to the inlet. It doesn't matter if it's on "Prime" or "On" the fuel seems to stay the same. I would take a picture but its all disconnected right now (valves).

I will read the write up on Cleaning Carbs (again). I really liked the Part I on the Mikunis, but I couldn't find Part II. Is it still in the works? The post on valves w/pictures is awesome it really made it a simple job-Thanks Fitz.

Before I start the carbs are there any really big Don't Do's I should know about since the write up only covers Do's. Any really important tips that a Noob like me is likely to be able to use to keep from pulling out all my hair. As you can tell from my Avatar it's pretty bad already.

 

Chacal has a great little screwdriver that is captive for the idle screws. I bought one and once I saw it I was glad I got it. It's just about impossible to mess up a screw using it.
I visited my local small engine repair shop and asked if he had any small fuel tanks laying around (not new) that i could use for adjusting float levels, and later syncing the carbs. He directed me to the back yard junk motor pile. In 30 seconds i spotted a Briggs&Stratton engine that had a 1/2 gallon tank and a fuel shutoff valve on the bottom. I scored that for 5 bucks. Now I just need to clean it out and set it up with some fuel line.
Use only screwdrivers in good condition, and buy a few cans of carb cleaner. I used Berkabile Gum Cutter on tough spots. It's not hard, just time consuming.

 

Wow what fun I had tonight with the shims! Here's what happened this has got to be new.

There were 6 I needed to pull out and record. All four intakes and the two outboard exhausts.

When installing the shim tool I discovered that both the exhaust side bolt threads were partially stripped-luckily it was only the first few threads. I used some PB and was able fix em, but it slowed the process.

5 out of 6 shims came out pretty easily (wish I had hemostats though), ..but the #4 intake shim would not come out. After almost an hour, I was in full on curse mode, mostly swearing at the bastard who must have put JB weld on the shim-Finally it came out after 6 small tools went at it. This shim was so old that there was no number to read, not even a remnant. It was being kept in by some fatigue on the metal (looked like symmetrical swirls) that had sort of bonded with the bucket. I ended up scraping a little damage into the area around the bucket trying to get it to break loose-hoping it won't be an issue. It's not in the area where the bucket actually seats but right around the area-I guess I could try and sand it down but I would worry about the shavings more than the little scrapes.

To try and determine the size of the worn out shim I laid it on a perfectly flat surface and using a magnifying glass w/bright light compared it to 285mm and 275mm shims. It appeared to be a 280mm, but can't be 100% sure.

God I hope the carbs are not this much of a pia. This valve adjustment is not a hard job unless this sort of stuff happens. Clearly these valves either haven't been done recently or were done incompletely. The shims I pulled were E1-270mm, I1-290, I2-285, I3-285, E4-275, I4-unknown?

Does anyone know if those numbers look like originals? Since the valves tighten over time those seem like pretty large shims.

Pulling the carbs next-Pray for me.

 

There is absolutely no way to tell if those are the original shims or not; the originally-installed shims varied all over the place.

Don't guess at the one you can't read. Either invest $12~$15 in a cheap digital caliper (worth every cent) and "read" it; or take it to a local garage, machine shop, the auto parts store, or even your neighbor--- anyone who might own a micrometer.

OR- Swap it with one you can read, re-measure, and then shim based on your "new" clearance.

Dude, you've gotta quit chewing up metal. All of this stuff requires a gentle hand. As long as you didn't damage the head enough to prevent the bucket from moving (and rotating) freely, you're OK, don't worry about sanding it.

Be sure to dip the new shims in clean motor oil upon installation; and be sure they seat fully. Sometimes it takes a bit of a "push" because the oil acts as a cushion, but they gotta be oiled.

 

Right did that (used shim I could read) and it was a 280, because putting in a 275 took it from .10 to .15. clearance. I won't be putting back any of the old shims. The scrapes are on the "beach" around where the bucket seats "shoreline" so at least 1/8" away from the bucket. It rotates freely. Believe me for the first 40 minutes on that shim I was gentle, but it just wouldn't budge (like it was welded to the bucket). I tried moving the notch into 4 different positions (180, 160, 200, 210 degrees away from the shim tool. And repositioned the shim tool at least twice at 180 and 200 degrees. It finally came out at 160 degrees, even then it took getting underneath with a blade to get it to nose up and then many pries with a repeatedly cleaned sharp small flatblade to get it to pop (Nothing at all like the other 5 they just popped up).

I really do need to ride today but... :-(. Never before have I seen the value of having more than one bike, NOW I get it.

 

I use a tiny flat-bladed screwdriver (the smallest screwdriver that comes in Craftsman sets) to pop the shims up, and my trusty hemos to lift them out.

You can get by with only one bike; but to do that you have to have gone through it completely first, so that it's like having a NEW 30-year old bike.

However, maintenance still needs to be performed. I did a mid-season valve adjustment this past summer; but since it had been put in spec 5000 miles before, I only needed to re-shim one valve. And it didn't take me off the road. When you check again 5K from now, you'll probably have a lot less work to do.

That being said, it doesn't hurt to have an operational spare or two.

 

I'm the PO. While I appreciate the "trust no PO" rule (I follow it too), I went through those carbs like a DI was going to check them. I followed the rebuild guide here and was paranoid about having to do the job twice. I went through every orifice with everything including welding tip cleaners. I verified every passage with carb cleaner. The sliders were squeaky clean and drop just like they should. Every consumable part was replaced. I was so careful about the bench sync that the bike took very little adjustment to sync them. I tested each cylinder with a Colortune plug. When I was done, I used it for daily commutes and took it to Deal's Gap for some small bike entertainment this summer. It ran like a top the whole time.

I admit it was the first time I'd rebuilt a carb since by Accord in 1990 and the first time I'd rebuilt a multi-carb assembly, but it was running great. When I sold it, the only issue I was aware of was that the charging system seemed to have an issue. I just ran out of time and needed to sell.

I'm open to questions and I don't take the assumptions personally. 8)

Thanks!

 

Yamatoman, welcome! The thing that has me scared about your carb work is the "I went through every orifice with everything including welding tip cleaners" part. Welding tip cleaners are not designed for this application. They can and do remove material from the tiny little passages, thereby changing the flow rate of the circuit.
Also, I went through my carbs the first time before I found the write-up on here. So, the float bowls didn't get the proper care. Bike ran, but not great. Second time through I had a better idea of what these carbs specifically need, so they got a proper cleaning. Ran better, but still not excellent. Third time through them I used parts from the proper source (Len) and actually got everything sealed that needed to be. Also, still found more little bits that escaped the first two cleanings.

What I'm trying to say is that you may have done an excellent job, but these carbs with their microscopic little passages need perfection. Not good, not excellent, not wow-that-took-forever-it-must-be-clean; they need spotless shiny surgical clean.
You may have had it at that point, but if the mixture screws where at 6+ turns out then the carbs are damaged.
Once they are cleaned to that level, they are easy to adjust. (Now, the V4 Honda Magna carbs...those are a PITA!!!)

Now that my carbs are CLEAN, my bike fires right up and purrs like a tiger. Runs like one too! Or maybe a gazelle....you get the idea.

 

I doubt they're damaged; I just don't think they're truly clean. They're Mikunis and have the tiniest passages it's possible to drill into metal.

No offense, but my original diagnosis still stands; besides getting the valves in spec (necessary for vacuum sync) I still think the carbs are plugged somewhere. If not, then it is possible that they were damaged by the use of tools that removed more than just crud.

Again, no offense, but I don't trust float levels until I see them for myself; you simply can't go by what someone else did, no matter how accurately it was supposedly done. It won't take ANY "doing" if the floats ARE set correctly; it wouldn't hurt to double check.

 

I totally get what you're saying. Is it possible I missed something? Sure. Did I damage anything? I seriously doubt it. The one thing i am is careful with things that cost if I break them. I don't bubba things.

I bought this bike to take a break from another project. Cleaning the carbs was both a learning process and something fun to do, so no step was rushed and all of he parts came from chacal. It would have been nice to have someoneone available to grade me though.

MercuryMan is always welcome in my garage. I'm back to wrenching on my RoadStar now, but my girls miss Maxine.

 

I had someone send me a rack of Mik's he couldn't get to respond to any kind of fine tuning.
After looking at the Jets IN the Carbs, using a Jewelers Magnifying Glass, we found the WRONG Jets, ... all-over the place.
We wound-up ordering New Jets from Len.

The Sizes of the Jets are engraved on each Jet.
You might as well double-check to be sure you aren't a victim of hacked-together Carbs built just to make a bike start, ... to hear it run.

 

Just to throw my two cents in you are having the same problem I had a few weeks ago. My problem was the caps on the vacuum tubes, you know the ones you use to do a vac sync, were not sealing properly. The air leak could not be detected even with propane. BUT as soon as I changed them ALL my carbs where rich so I had to reset them. Before that she ran really good but the engine heat was enough to case them to warm up and leak. And the rubber did not seam to be hard at all. But it was enough to cause a leak.
Just my two cents.

 

Thanks Groundhugger, I haven't checked those caps because they look brand new, but I will now. It's interesting that this all started during the first time the bike had a chance to really get hot. I was stuck in Bikes, Blues, & Barbeque traffic on Dixon Street in Fayetteville for about 15minutes and the problems cropped up then. Prior the longest the bike ran without good air was ~1minute (red light). So maybe the heat caused a little leak up there. I have been busy but will be back working on it tomorrow, will replace those caps and see what happens.

 

As these Bikes age ... the O-ring between the Manifold and Head loses resilience.

Replacing them and tightening the Manifolds is a risk due to the SOFT Steel Cap Screws fastening the Manifolds which seize and break all too easily.

Sealing the back-side of the Manifold to the Head with a BEAD of Sealant "Smooched" into the joint will prevent breaking-off a fastener and the related Horror-show getting a seized fragment extracted.

 

So did my ROCK HARD ones. It's really quite phenomenal, they look nice and spiffy-new, while in fact they become absolutely rock hard. As in, can't even "squish" 'em with a pair of pliers.

 

Update and no good news :-(

Valves are done-within specs. Pulled carbs and didn't see anything wrong/dirty. Of course I am no expert on these Mikuni's. I didn't break the rack, so can't say I saw everything but what I did inspect looked the same from carb to carb and it all looked really clean. I suppose breaking the rack is next.

Put it all back together and problems remain. 3&4's pipes are getting hot and will change the idle with adjustment of pilot screw. 1&2 are not as hot and it seems like #2 changes idle just a bit, but nothing on #1. Unlike before, Idle wants to hang, won't return quickly and once it does it wants to idle around 1000 or eventually just dies.

Just to recap. Ignition system totally in spec. Plugs new and good. Replaced manifold caps (to be sure) and no vacuum leaks anywhere. Carbs passed clunk test, float levels are right, no varnish, no blockage, o-rings are new.

Also just to add to the fun. Replaced brake lines but the screws on master are totally stripped. The choke cable broke at the lever (was not abused just slacked and it broke!) and that screw is stripped-cable can be replaced w/o removing screw (small +). The screws on the ignition cover were stripped as well, but I got them off with an impact driver and replaced them with allen bolts.

I want to say thank you to everyone for your input and help. Unfortunately I am out of money, out of time (college is taking all my free time), out of patience, out of ideas. What is really depressing is that I got this bike to save money commuting to school and that hasn't worked out too well. I am back to spending $60 per week in gas and have now dropped every spare penny I had into the bike and its going nowhere. My plans are to pull the carbs again (time willing) and see if I missed anything. But whatever I find will have to be free to fix at this point. Maybe next year I will have the Maxim up and running. Right now it seems like I made a mistake.

Once again thanks to all for trying to help me. I will update if anything changes but for now...Houston we have a problem!

BTW- I have a great big SUV for sale if anybody is interested. Plenty of power and predictable gas mileage.

 

Maybe when you pull the carbs next time take a real close look at your manifolds. I noticed on one of mine this weekend that there was rubber separation from the vacuum tube sticking out of the top. I smeared it with high temp RTV, and FINALLY installed my new vacuum caps from Chacal. My idle went rich on me, and smoothed a little more from what it was. More tuning to do...

I'm tempted to change my manifolds. Has anyone tried loosening them while the engine is hot (and the aluminum expanded) with sucess and not breaking a bolt?

 

You can't just look at the carbs.

You need to "field strip" them http://xjbikes.com/Forums/viewtopic/t=31061.html and then shoot carb cleaner through all the tiny passages to be sure they're all truly open. A lot of those little passages aren't straight, you can't tell anything by just looking at them. Your symptoms still point to a blocked passageway or wonky float. All you need more of at this point is patience.

Re: changing manifolds on a 550. We're lucky--- none of our (intake) bolt holes go all the way through, so the chances of breakage are somewhat reduced. When you're ready to try: Get some Kroil: http://www.kanolabs.com/google/ and soak the bolts/manifold joints for about a week prior.

 

I have Kroil... Good stuff but it stinks!!!
My carbs slip into the manifolds easy. I'm thinking they are shot. Cracked up pretty good and probably just time to get rid of them...

 

Thanks bigFitz. I did have them apart but I didn't go the whole nine yards. After looking through the multitudes of carb info here, and checking everything else off the list that it could be. I have come to the conclusion that you have identified my problem. What kept me from going the "whole nine" was time, impatience and the fact that it ran so good before. I now believe that it was on the verge of having issues (or something caused issues to develop) and sure enough they cropped up or crapped up might be a better term. One thing-since 1&2 are down are you thinking that they both have a blocked passageway?

I'm not giving up so next - cleaning up garage and creating work space to go the field strip route. I only wish there was a part II to your Mikuni post, a step by step of rare Mikuni BS28 carb rebirth! I understand what to look for with respect to "not clean," but how will I know if any of those little parts have been damaged/changed enough to cause my issues. What's your opinion about using SeaFoam as a cleaner/dip, then finishing with carb cleaner and compressed air?

Wish me luck and patience and hopefully I won't have to ask too many boneheaded questions.

 

Why risk dipping these Carbs when they'll clean-up quite nicely just being exposed to Carb Spray and hand cleaning.

Prop the Bowls level.
Shoot some cleaner into them.
Put the Float Valve, Pin and Jets in the Bowl to soak before you do them.

If you have a Varnish Stain that is almost bullet-proof, ... then you dip.
But, then you'll likely need Shaft Seals.

For Mikuni Carbs you should be able to SCRUB the Parts, ... by hand.
Get a Hard Toothbrush.
ScotchBrite Pad
Pipe Cleaners (White, long - - Craft store.)
Bubble Ear Syringe -- Power Flushes passages.
Q-Tips
Time.

 

Exactly what I was wanting to know Rick! Thank you for sharing your aspirated wisdom. I was afraid of dipping and just needed to hear that it wouldn't be required. I have never done a complete break down of a carb and never, ever messed with 4 carbs in a rack so I am a little paranoid about it all. Your experience and advice are evaporating my fears, now I just have to go evaporate some deposits. On the plus side I do know what clean is and worship at the "church of clean!"

Below is a pic of 2 of my 31yr old union bolts after I took them to the chapel! They aren't brand new but I removed the majority of their blemishes. Bummer I forgot to snap them when I pulled them out, but suffice to say they looked like an overweight crow had crapped on them.



I'll stop preaching now and get back to biz.

 

Hey man, how's the project coming? It sounds like your experience has been pretty similar to mine! I'm in Springdale as well, so let me know if you want to collaborate.

 

What up TR? The 550 is running nice, the problem was two fold. The PO had cleaned the carbs very well, but the floats were just out of spec low. The strange thing was that every part of every carb was spotless except for the 1&2 pilot circuits. They were being blocked by some small black plastic looking crap. I don't know where it came from, but I suspect the K&N filter which didn't seat real well let something past and it found it's way into the pilot passages.

I am still trying to do more upgrading and refining like replacing the glass over my speedo (it's cracked) and things of that nature, but mechanically the 550 seems really fine. It's plenty fast to 90 and awesome on the gas mileage. I wish I had progressive springs and new rear shocks but that will require $$ I don't have. I have also been repairing a '74 Toyota truck so I have spent all my reserves for now.

How long have you had your Seca and how is your situation? Glad to know I am not the only XJ'er in the 'Dale.

 

Awesome, I'm glad to hear you got her running well!

Eh, I've had mine coming up on two years now, and it's still shitty lol. I won't clog up your thread with details, if you're interested it's here: http://xjbikes.com/Forums/viewtopic/t=31937.html

Maybe i'll see you around sometime!