Questions from newbie re: '81 Xj550

Hi Guys! I've been working on an '81 XJ550 (with 20k miles) for a few months now, time permitting, and reading everything I can find re: these bikes, but this is my first post. So my very first question is: What's a good price for a spare rack of carbs? As in, if I see a rack for this price or less, I should jump right on it. I've been reluctant to tear into the rack I have, but I know I'd feel much better about it if I had a spare rack.

What I've done so far:

De-rustified and coated the inside of the tank, rattle-can painted the outside. Turned out ok, but after the ridiculous number of hours I spent on wet sanding, rubbing compound, and polishing compound, I kinda wish I'd just paid to have it done professionally.

Got the valve clearances into spec, they were all .05 too tight, except for one that was .1 too tight. Had a b##ch of a time with that tool that holds the bucket down to keep the valve open. Wish I'd known about the zip tie method before I ever bought that thing.

Pulled the carbs and replaced the float needles and bowl gaskets. No more gas pouring into the airbox. Did not split the rack, and did not get into the top of the carbs. Was hoping that seafoam would bail me out. Right now it has about a gallon of gas in the tank and maybe 1/3 of a can of seafoam, and has been ridden maybe a half a mile with that mix. Was hoping a heavy dose would clean things out for me. Rack came off easily, but took me forever to get it back on. What a PITA.

I made the little hose thingy to check the float levels. Only checked #1, found that my gadget leaked and need to try again with a different epoxy, but the level for #1 looked ok.

Got a carbtune pro, but haven't synced yet. I'm thinking it needs to run a bit better first.

Plugs 1-3 get sooty, but plug 4 looks good. At first I was thinking that cyl 4 wasn't firing, but all 4 header pipes get hot so now I'm thinking that cyl 4 is just running much better than the rest.

When I get it running, it does idle. Not well, but it does. However, under load it wants to be revved or it'll die.

Here's something I find interesting. When the bike has been sitting for a while, maybe overnight, it will start immediately on first try, and run for a second or 2 before it dies. After that, it becomes very hard to start, and of course after some time cranking the bat gets weaker and weaker. The bat is a fairly new (april) conventional, but after reading about how sensitive these bikes are to voltage levels and how they don't charge at idle, I went ahead and got an AGM bat that's supposed to have 180 cca instead of 112, but it wasn't the miracle cure I was hoping for.

So the next step is to pull the rack again and do a thorough clean/rebuild, right? I know, I know, I'm just not looking forward to it.

Rickster
81 XJ550 20,700 Miles
Austin, Texas

 

Yep.

Gotta get into the whole carb; emulsion tubes important; tiny passages important. Condition of microscopic o-rings on mixture screws important.

Exploded Mikuni: http://xjbikes.com/Forums/viewtopic/t=31061.html

Float levels need to be accurately, individually wet set. VERY important. The spec is only 1mm each way.

Then do as accurate of a bench sync as you can.

THEN put them back on the bike, and with the YICS blocked, do your running vac sync.

I have two spare racks of Mikunis. The "good" rack cost $50 off eBay; the "parts" rack, $22.

 

He has the non-yics engine correct?

If seafoam or the like would work to any advantage it would be listed in the FAQ section. I have read posts of many trying it, but nobody with positive results.

Your going to have o tear into them much deeper than the floats. Complete disassembly is required. Pay close attention to the fuel enrichment and idle circuits.

That 550 is a good bike. I had one and drove it 33,000 miles then sold it. It ran good and kept up with the Ninja's

 

The bike in question is apparently an XJ500, and may or may not be YICS-equipped.

*EDIT**IGNORE-- my response is to a different thread, wasn't paying close enough attention***

 

It's definitely an XJ550 Maxim USA model, confirmed by digits 4-6 of the VIN. It is a YICS engine. I haven't made the YICS tool yet, but that looks pretty straightforward.

Anyone have any experience with the carb rebuild kits that you see around, specifically what is and isn't included. Float needles, seats, and bowl gasket I can handle, but the pictures usually show a couple of o-rings as well. I'm curious if those are the for the drain screws, or what.

There's an o-ring at the very bottom of the pilot screw, right? Is that what Chachal is referring to as the idle mixture o-ring, or is that something else.

I made an offer on a spare rack, we'll see what happens there.

Thanks guys!

 

Yup, you got it, thats the idle mixture o-ring. It's a small one.

Study up the carb articles that Chacal has in his section that the Pro's on this board wrote up. They are well written and are picture rich. Do it all. Bigfitz posted a great blow up picture, print and study it. The o-ring you question is on the pilot screw. Notice how dirty the emulsion tube is in that picture!

Here's some more: From XJForever's section (the information overload hour)

- REMOVING THE DARNED THINGS!:

xjbikes.com/Forums/vie...29695.html



- CARB REBUILDING BASICS:

xjbikes.com/Forums/vie...14692.html

and

xjbikes.com/Forums/vie...14751.html



- CARB REBUILDING ADVANCED ---- X-RAY VISION!:

www.xj4ever.com/inside...0carbs.pdf




- HITACHI CARB REBUILDING:

www.xjbikes.com/Forums...=3649.html

and

mok.fileave.com/Hitach...akdown.pdf



- MIKUNI CARB REBUILDING:

www.xjbikes.com/Forums...=3633.html

and

www.xjbikes.com/Forums...=3690.html

and

www.xj4ever.com/mikuni...eaning.pdf

and

www.mtsac.edu/~cliff/s...torial.pdf

Note that the above link shows the rebuild for the BS28 series of Mikuni carbs (same as on XJ550 models) that are off a Suzuki, and while some minor differences exist ( i.e the choke plunger system and the locknuts on the synch screws), 99% of the information (and pictures) will crossover to the XJ550 model carbs.




- CARB VACUUM PISTON OPERATION:

Having the carb piston bore fully polished is an incredibly important task when rebuilding a set of carbs, as any restriction to the free and almost friction-less movement of the vacuum piston will create a variety of performance-related problems. You can review this issue (the vacuum piston "CLUNK TEST") at:

www.xjbikes.com/Forums...=1640.html

and see a nice video of a clunking piston at:

xjmadness.myphotoalbum...clunk_test

And the reason you want your vacuum pistons to operate as closely as possible to a "zero-resistance" state is because they must be able to perform, constantly, in the following manner; and if not, tuning and performance becomes troublesome or downright impossible:

www.youtube.com/watch?...re=related


Note closely the difference in vac piston operation between a no-load condition:

www.youtube.com/watch?v=sMKGMCimV2w

and how they operate under load:

www.youtube.com/watch?v=tR63vrfhwr8



- THROTTLE SHAFT SEALS and SCREWS:

NOTE: these throttle shaft retaining screws are an absolute BEAST to remove, and it is very easy to destroy the screw heads as well as the throttle shaft threads while trying to remove them---if proper precautions are not taken. You will want to review the information in this forum thread before attempting removal:

www.xjbikes.com/Forums...=8011.html

and

www.xjbikes.com/Forums...17628.html

and

www.xj4ever.com/hitach...0seals.pdf



- CARB ENRICHMENT ("CHOKE") CIRCUIT CLEANING:

xjbikes.com/Forums/vie...=8918.html


a) shine a strong penlight or mini flashlight into the bottom of the bowl, where this jet passage "intake" is located. Look through the top of the bowl down into the jet passage "outflow" passage (this is the passage that the brass suction tube in the bottom of the carb body actually fits down into). Focus your eye carefully on the jet opening and make sure it's clean. P.S. it helps to do all this while in a darkened area.........see the picture "pen light test" on page 2 of this forum thread topic for a great image of what you want to see!:

www.xjbikes.com/Forums...=4050.html



- CARB PILOT MIXTURE SCREWS --- ALL YOU EVER WANTED TO KNOW ABOUT THEM:

www.xjbikes.com/Forums...18265.html



- CARB PILOT MIXTURE SCREWS STUCK?:

You're not alone.........

xjbikes.com/Forums/vie...32017.html



- CARB BOWL DRAIN SCREWS STUCK?:

You're not alone, either.........

xjbikes.com/Forums/vie...=4281.html



- CARB FUEL LEVEL SETTING:

Here's the Holy Grail on this subject:

www.xj4ever.com/settin...levels.pdf


The picture on page 4 of this thread properly illustrates the factory-recommended method of checking the fuel level; the tube should be wrapped around to the side of the outer carb, and "centered" front-to-back along the body.

www.xjbikes.com/Forums...tml#149243



- CARB PRELIMINARY "BENCH-SYNCH":

xjbikes.com/Forums/vie...=6366.html



- CARBTUNE "SYNCH STICKS" USAGE:

www.youtube.com/watch?...re=related



- YICS SYSTEM SYNCH TOOL USAGE:

www.xj4ever.com/HCP546...20tool.pdf



- COLORTUNE TUNING PLUG USAGE:

www.gadgetjq.com/Vulca...e_Test.wmv

and

www.gadgetjq.com/Vulca...e_Test.wmv


and

www.youtube.com/watch?...re=related

and

www.youtube.com/watch?...re=related

and

www.youtube.com/watch?...re=related



- PREVENTING BROKEN CARB FLOAT PIN POSTS:

xjbikes.com/Forums/vie...19168.html



- FIXING BROKEN CARB FLOAT PIN POSTS:

xjbikes.com/Forums/vie...17843.html

 

Just out of curiosity, what carb circuit can I not clean if I don't split the rack?

 

You can clean them all, but you split the rack to put in new shaft seals which is a good idea on any 30 year old set of carburators.

 

I wouldn't replace Mikuni throttle shaft seals "just because." Sometimes they're fine; sometimes not. You need to be careful doing the rest of the service that you don't inadvertently damage them.

You need a SERVICE MANUAL. Both the factory and aftermarket (Clymer, for the 550) books show the "basic carb service" procedure; they just don't admit to the existence of the pilot mixture screws. Those need to come out as well; the book wasn't written with restoration in mind.

 

Thanks guys. I do have a Clymer on order, but it hasn't arrived yet. Maybe it was shipped via carrier pigeon.

I gonna try this without splitting the rack. Will post follow-up results in a few days. Wish me luck!

 

Holler if you hit a snag.

Meanwhile, check this out. This is how far apart you can take a Mikuni without splitting the rack/removing the throttle shaft. http://xjbikes.com/Forums/viewtopic/t=31061.html

 

I've made some major progress, but not quite there yet. I put about 4 miles on the bike yesterday, and it now idles pretty well but struggles a bit in the midrange and higher RPM's. I did take a few shortcuts out of necessity, and very possibly that's the source of my issue, so I would welcome any advice or comments.

Valves clearances are within spec. I removed and cleaned everything I could in the carbs without breaking the rack, with the exception of the o-rings in the idle mix/pilot mix/whatever you call that circuit, the one hidden behind the metal plug. I figured I didn't have any replacements for them anyway, so what was the point of removing them and possibly damaging them in the prcocess. I did spray well in there.

I did remove every single jet and the enrichment plungers and cleaned everything. Several of the emulsion tubes were pretty bad. I passed a guitar string (a wound one, so it would have a slightly rough texture) thru the pairs of opposing holes for cleaning. Some took a bit of work. Cleaned every passage and orifice I could find, poked wires as far as they would go thru every little passage I could find. Wet set the float levels. They're pretty close now if not spot-on.

Even though I didn't break the rack, I tried to bench-sync the carbs but evidently did a pretty awful job of that. The bike would run but not idle. A vacuum sync showed just how far off they were, and once I got them pretty close the bike idled down just fine.

As for the sync... I tried to make my own YICS tool using some instructions I found on HAP's site. Had to improvise a little. The instructions called for #6 washers between the plug parts and the spacer parts, and it seemed like these were catching in there somewhere, and if I could get them to pass thru, then I couldn't get them to pull back out. At one point I sprayed WD40 in there to help lubricate and clean a little (WD40 is a pretty good solvent for carbony spooge stuff) and that helped get the tool in, but it wouldn't run worth a crap after that. Not sure if it was because the ports were now blocked, or because there was now WD40 in the intake, but I finally bailed out on the whole YICS thing. So as of right now, the carbs are as in-sync as I can get them without blocking the YICS passages.

For the pilot mix, I do not yet have a color tune kit so I set them all to 2.5 turns out.

So, my questions:

1) If they call that circuit idle/pilot mix, and the bike idles pretty well, can that be exonerated from contributing to higher RPM issues?

2) That's an air passage, right? So backing out the screw should allow more air, making the mix leaner? Should I try 3 turns out?

3) How much difference can I expect between syncing with and without blocking the YICS passages.

4) Since I crashed and burned on building my own YICS tool, is it worth buying one from Chacal?

5) At multiple points in this process, I cleaned the plugs with a wire prush (sooty) and sprayed them with contact cleaner. Back in my 2-stroke days (motocross), everyone used to say a fouled plug was unsalvagable. Is this really true? Should I expect a new set of plugs to make a difference?

6) Where do I go next?

I should point out that I'm having transportation issues, so my priority is to get this bike road-worthy. I'll gladly accept less than optimal power or mileage, so long as the bike can can get me around reliably.

Thanks in advance for your advice and comments!

Rickster

 

I know the rubber washers seem trivial, but they are a must. There is also a steel washer that sits on top. I got mine out of my 82 550 and they were pretty well cooked.
I also cut off a small bolt that threaded into my emulsion tube end. Then I chucked it up in a drill and polished the tubes with Mothers polish per Rickomatics instructions. They turned out like new.
I know the others will ask... did you wet set the carbs? Did you add an inline fuel filter to keep trash out? How is your petcock screen? Is the tank clean internally?

 

Yep, wet set the floats. Clamped the rack into a workmate, adjusted level in both directions. Bike already had an inline fuel filter. I never could get the fuel line to seal very well to my aux tank, so I watched very carefully each time I filled the bowls while checking the float levels, so I'm confident that fuel flows fine thru the filter. I opened the petcock up and cleaned everything, but don't recall seeing a screen in there. The tank was cleaned, de-rusted, and coated internally using the Eastwood kit. I actually did that back in May, so the coating cured for at least 2 months before it had any gas in it. Also, I drained the tank (with the petcock on prime) to get out the gas/seafoam mix prior to putting in fresh gas, and the gas that came out looked clean. A bit orangy, I assume from the seafoam, but no sediment or suspended particles or anything like that.

 

There is a screen on the standpipe of the petcock but sounds like yours is fine. Maybe someone else has some ideas

 

Okay, I just ordered those o-rings and washers, along with a YICS tool and Colortune kit from Chachal.

What are the chances of being able to remove the old o-rings without pulling the rack back off the bike? It's not the pulling it off that bothers me, it's the putting it back on.

Also, what would you recommend pulling them out with? Maybe a straightened-out paper clip with a little hook on the end?

 

Do-able. Pull your tank, then take a long pin like you use for sewing and bend the very tip at 90 degrees. Reach in and fish the o-rings out. You are also looking for the washer too.
You may want to squirt those passages again once you get them out with some carb cleaner.