carbs carbs carbs

Did you dip the Carbs or use any solvent to clean the Pilot Fuel & Air Passages that might have caused the Pilot Mixture's tiny O-rings to have deteriorated?

 

Those 3 very very small holes are called your "Idle bypass holes". I don't think gas is burning inside the carbs and I wouldn't pay too much to the black stuff right now. I'm thinking that you've got some blowby and you're sucking it back in through the carbs.

Look very closely where the butterfly plates get close to the carb bodies. Look for signs of rubbing, especially along the sides where the shafts go through the bodies. Getting the butterfly plates aligned correctly is very easy, but it can require some finesse. Have you done carbs before to this level of disassembly?

If you're completely confident in the installation and placement of the butterflies, then how bout you put the rack back together like you had it before and take some pics of the linkages?

 

Just for shids and grins, ... "Take-a-drag' on the Vacuum Hose that goes from
the Manifold to the Petc0ck.

You > shouldn't < taste gas.

If you do, ... the Petc0ck Membrane is perforated letting FUEL run-up the rpm's.

 

+1 Rick. that totally slipped my mind and makes sense. I will check it out and either way, replace it since its been on there since I purchased the bike 3 years ago. carb dip was used on the initial overhaul clean 9 months ago. check out my thread "enough rubber?" since then all rubber has been replaced via Len's shop/catalog. carbs were overhauled then and yeah I've torn it down this far before obviously

Polock: no there was never any backfire which is why its surprising. and more confusing enough its behind the butterfly. the engine was consistently racing as it got warm and running with no choke too, no hesitation

i guess my whole attempt tonight is to take the shafts off each individual body, inspect rubber parts and re-lube 'em. put it back together and I will definitely take pictures of each linkage/spring on throttle shafts. and this time I will be even more pristine on the orientation of 'em butterfly plates. sounds like even the slightest angle once tightened down may cause the rack to go outta wack.

i appreciate your help guys. no way would I ever have this much confidence gained within a couple years from fellas who share experiences and advice to others

 

Don't make work for yourself.
If he Seals are OK, ... just lube them.
Shoot some Silicone Spray into a Glass and use an Artist's Brush to deliver the Silicone to the Seals.

Stand the Rack on-end.
Brush some Silicone on the Shaft and let it flow down to the Seal.
Work the Linkage to get the Silicone spread on the Seals.

Tip the Rack 180 and do the opposite end.
After the Seals are treated; lube the Shaft and Bore.
I use Marvel Mystery Oil. Its safe.

Look at the Linkage.
If any of the Couplings and Sync Screw adjustment arms are not "True" and at correct right-angles, ... carefully place the in proper alignment.

Replace any Sync Screw that does not "Feel" right or is even partially stripped.

Add a Nylon Washer to the Idle Adjustment Rod.
Place the Washer between the Spring and Rod.
So the Spring makes contact with Nylon allowing the Idle Rod to be easier to adjust.

 

Please don't shoot the messenger.

Black soot inside a carb, on the "backside" of the butterfly, came from the combustion chamber. Had to. The only way that can happen other than a backfire is a valve that's not sealing properly. You said the soot was in the #4 carb. Wasn't #4 the cylinder that gave you all of the grief when you were trying to vacuum sync?

Disconnect the TCI, and spin the motor with the carbs off. Put your hand over the #4 intake manifold while doing so. You should get vacuum pulses when the cylinder is on the intake stroke, period. See if you get any "outbound" chuffing.

Run your finger around the inside of the #4 intake manifold, and down into the intake port, and see if the manifold and port are lined with soot. Intake tract should be cleaner than clean.

I'm wondering if the #4 intake valve isn't seating/sealing properly. Sorry.

 

Oh its working properly. dang I wasn't expecting such a great vacuum. the back side of my hand felt like it got a hicky. all four provide vacuum pulses of about equal greatness.

each carb is getting a quick cleaning/spraying of carb cleaner (particularly through the pilot mixture screw hole and out the jets) since all rubber is off tonight. plan to dry everything, lube the rubber again, and get back to fun...now get your mind outta the gutter

would household oil work rather than marvel mystery oil?

 

I'm sure you'll get vacuum, or the motor wouldn't run. I was looking for any "reverse pulse."

And after a lot of thought, the problem wouldn't reveal itself that way anyway, because the motor's not HOT.

QUESTIONS:

Did you rub your finger around the inside of the manifold to check for soot?

Is #4 the cylinder that got a new piston?

Here's what might be going on, especially if #4 is the cylinder that had the issue; but even if it's not.

I think you have a "wounded" valve. A valve that seals fine COLD, but once heated up to op temp, distorts enough so that it quits sealing completely. It would explain the soot in the carb as well as all the grief you got trying to sync, AND could even be what's pushing the butterflies open when they should be closed.

It would explain a lot. Again, sorry.

Oh and NO don't use "household oil." Better to use MOTOR oil even. Remember how harsh the environment is once the motor is warm. Forget "household" (for good) think "automotive."

 

Yes: no soot anywhere, clean as a whistle.
No: #1 is the cylinder that got a new piston.

=> either way, I'm still leaning towards *a* carb issue. just last week I checked compression immediately after a hot ride (yes, had the racing problem then too) just for shins and grits: all were even across the board 135 near 140 psi


So back to my carb reassembly tonight. got 3 outta 4 carb butterflys re-installed. I verified the plates alignment with use of a flashlight underneath shining down the carb bore to see the even moonlight-crescent disappear as the spring closed each butterfly. couple questions:

1. With a butterfly on the shaft, should there be any play side to side before placing the e-clip on the other side? carb #3 which I didn't finish tonight has approx 1 mm or so of free space between the large spacer and the throttle linkage itself. almost big enough for another plastic washer like the one on the other side of throttle shaft.

2. How tight should the 12mm nut be on #2 and #3? upon disassembly I was able to loosen it a socket and my hands. didn't need the wrench part. I have the lock washers on them yet it was still loose enough for my manly hands to loosen 'em.

P.S. carb re-building always takes a lot longer than you think it should.

 

Coming in late here with a couple thoughts.

Is it possible that the throttle cable, or throttle tube might be hanging up, or dragging from dirt/corrosion?

Lube the cable with clean oil. If the oil comes out the other end dirty brownish looking you have corrosion inside the cable.

Clean/Lubricate the throttle tube with silicone grease where it rides inside the switch/control and around handle bar.

Ghost

 

OK, gotta agree on it being carburetion (or vacuum) related then.

As long as the #4 intake tract was clean, and you did get good numbers on a "hot" compression test, we'll rule out the valve. The soot on the back of the butterfly must have been from a backfire during the synchronizing fiasco.

We need an Hitachi expert here; all of my "minute" experience so far is on Mikunis (and Amals) so I can't answer questions that granular (yet.)

 

Hey Moell---

While you have things apart, could you double-check the numbers on every jet and which positions you have them in? Just wanting to make sure that you have the right ones in the right positions as some of them are accidentally swappable.

Dave Fox

 

When I'm putting the carbs back together, I let the throttle plate butterfly drive the position of everything else:

1. Put the throttle shaft through the carb body along with any necessary linkage hardware bits
2. Put the butterfly plate through the shaft and put the screws in loosely so the plate can still move around
3. Wiggle and adjust the shaft and plate such that it will absolutely seal all the way around (a very bright light and magnification helps with this)
4. Move the shaft axially to determine how much side-to-side play there is, and then adjust the shaft so it's about in the center of it's range
5. Tighten down the butterfly plate screws and verify that it still seals perfect and everything moves freely.

After you've gone through that, if there's "excessive" (relative term) slop on one side or the other, you can shim it with an appropriately sized spacer. Of course, you may have to take it apart again depending on which side of the shaft is sloppy.

As for the linkage nuts... You shouldn't be able to loosen the 12mm nuts with just a socket and your fingers. Don't torque them "grunt tight", but you should need some sort of mechanical advantage to get them loose. I don't use a torque wrench, but they should be tight enough that the split lock washer is full compressed and then maybe an eighth of a turn beyond that.

 

I don't believe the butterflies are the problem. I don't believe that there is enough clearance for enough air/fuel mix to get through to cause such a high idle.

Moell.....once again I'll ask.... (maybe you answered and I've just not seen it) have you tried putting a different set of carbs on the bike?

Dave Fox

 

no, I don't have any other folks around here that I trust having a running 4 cylinder carb rack to use. gonna put these back together and if things still become outta wack I'm gonna shoot somebody. rather, I'll just have you examine them and try using the rack on a 650.

didn't get any progress today. family reunion and long-distance cousins visited all evening. I love my bike but I put God and family at the top of the list. 'night folks

Oh, and all the jets are "stock" numbers according to Lens catalog.

 

Having the correct jets doesn't mean you didn't slip up and accidentally swap positions, as is easily done on Hitachis.

While it's apart, triple-check.

 

That's exactly what I said, and that is EXACTLY why I said that.

Dave

 

Moell-- here's a thought.....I'll look around and see if I have an extra rack around. If so, maybe we might be able to work something out for you to try it. Let me see what I have.

Now, here's another thing to double-check -- I had one bike that would run fine but would race like the dickens when I'd turn the wheel toward the right. The cable was fine. The connections were fine. The carbs were fine. The problem turned out to be that the cable was routed in such a way that whenever the bars would turn even slightly right, it would bind and get caught between two brackets. Turn anything toward straight and left, it would free right up. I rerouted the cable and the problem dis-appeared. I know you've been through everything time and again, but something to triple-check.

Dave Fox

 

I'm going to back up a little and pull info from some of his previous posts:

If the problem is truly as described above, then:

It's not the throttle cable.
It's not the choke cable.
It's not jets misplaced.
It's not the petcock.
It's not a vacuum leak.
It's not the slides hanging up.

If that list is accurate, it's something mechanical in the rack itself.

 

Make-up an Aux Return Spring for an experiment.

Use Rubber Bands and Xmas Bulb Hooks.
Latch-on to the Linkage of 2 & 3 and bring the two together.
Hook the 2 Rubber Bands to one central location.
You can even Loop the Rubber band over Sync Screws.

Just give the Return Springs some help to see if they aren't part of the problem.

 

Was thinking about this some more and I may have jumped the gun with ruling out some of that stuff above... You said:

So the engine is hot, and your idle is racing.
You disconnect the throttle cable and it's still racing.
Then you push down on the two outside screws and the idle drops to where it should be.

So... What happens when you stop pushing down on those screws?

Does the idle go back up to 4000RPM, or does it stay where it belongs?

 

The idle goes back up to 4k or so. and by pushing down, I have to literally push pretty hard enough that I get an indentation in my fingers of the screw head. the best way to describe my problem is that its thirsty; it wants more and the vacuum is sucking harder, either keeping the slide bores up and/or the butterflies open.

Question about the slide bores/diaphragms that sit below the carb hats. Do you folks use anything on the slide diaphragm to edges to be certain the top is seated properly in the groove of the carb? I was thinking about using clear silicone since I've never used anything before. Perhaps they are seating correctly... just throwing 'off the wall suggestions.

my plan is to have them completely reassembled by tomorrow night.

nobody answered this yet. perhaps this is part of the problem too when I reassemble the rack its enough space to bind the rack? I can take a picture tonight for you to see if it helps.

 

anyone?

luckily I still have my younger brother's '93 XJ600 to ride since he's away at college. its has clutch issues but excellent carb operation which makes me jealous

 

Glad I asked. I was interpreting the other way. Bummer too, because it's unfortunately not as clear that it's a strictly mechanical issue. With that in mind, here's the revised list.

It's not the throttle cable.
It's not the choke cable.
It's not the petcock (unless it's causing a vacuum leak).
It's not the slides hanging up.

I've removed misplaced jets and vacuum leaks from the exclusion list because it could be related to one of those.

As for the diaphragms, I don't use any sealant on them. The hat does a pretty good job of squeezing them.

 

Pushing down on the Linkage ... hard enough to make an impression in you finger, ... may have caused a Throttle Plate to become deformed.

That Throttle Plate(s) would fail to close when the The Linkage is supposed to be shut.
Air Leak.

If one or more was deformed, ... it would have Bench Syncing a bit of an adventure.

What did you use to Bench Sync?

 

one of my father's honeybee business cards cut into strips about .25 inch wide. done it so many times I could do it again with my eyes closed. and will have to once the rack is together tomorrow night hopefully. we've got a beautiful 70 degree afternoon weather this week in Ohio

 

someone mentioned they couldn't get their engine to idle down....it could have gas in the oil. It happened to me once and it wasn't much gas at all. Left it on pri for just a little to long.

 

as of this evening, I have completed the following:

1. throttle cable and plastic housing unit on handlebar lubed
2. throttle shaft seals lubed with clear silicon grease from Napa shop
3. fuel o-rings lubed with clear silicon greas as well
4. carb rack reassembled on two sheets of glass sitting on the steel table saw out in the barn and mounted together using locktite on mounting screws as well as butterfly plates in each carb.
5. applied silicon grease on main idle adjustment screw and plastic washer
6. jet number/location verified for each carb
7. another quick shine polish along carb bore where piston/needle/diaphragm slides up & down.
8. bench sync using 1/4" strips of business card
9. quick sniff test on my oil ~ there was a small odor of gas
PICTURE TIME:


Springs and linkages between #3 and #2


Spings and linkages between #4 and #3


Springs and linkages between #2 and #1


Overview of all three sync screws and return springs


Close-up picture of #3 and #2 throttle shaft connection


Close-up of #2 and #1


Close-up of #4 and #3


Overview after bench sync complete

QUESTIONS:
I noticed when I do a clunk test with carb hats off the slides drop instantly and with a clunk. When I put the carb hats on the slides drop and with a nice drop sound, but its at just a slightly slower pace as if the air suction from the diaphragms are ever-so-slightly holding it up. I've got videos on youtube that I'm trying to upload. listen carefully to them and give me your thoughts. I'm serious; these slide bores are clean and shiny as a whistle

clunk test without carb hats
clunk test with carb hats on

WARNING: the video may be slow at buffering and loading. I had to use photobucket since youtube was taking forever to upload

also, anyone else have thoughts on this?

 

At a glance, ...

The 1,2 & 4 Return Springs look OK.
That Spring on 3 looks loose.

 

it not. in fact, its bent upwords because of the tension the spring retains on the throttle linkage.

looks good to everyone else I suppose. haven't heard any yelling or reasons to not move forward then

 

hmmm... anyone view the videos? how do the drop compared to yours? come on, I need more input than just from Rick

 

I wasn't taking a poll.
I simply said that, ... that 3 Spring looks funny to me.
That's what it looks like in my opinion.

Given that he has to press on the Linkage to lose rpm's, ...
That Spring sticks out.

Looks funny to me.

 

it's been awhile since i checked but the clunk with the hats on seems kind of fast to me.

 

thanks guys for your assistance and putting up with my problem(s). glad to say whatever the problem was, has disappeared even though I can't rule out what specifically could have been the problem. bike is running well tonight as everytime I pull the clutch the idle drops rather than racing, and will not steadily increase in idle as the bike warms up.

this thread will not cease however. I will update periodically considering I decided tomorrow I plan to ride the bike to work (39 miles one way). thanks again all for your support

 

You're description of the slide tests sound fine to me, both ways. The springs look ok to me, too. So, we sees what happens after your ride. Let us know.

Dave Fox

 

They CLUNK during the Test, ... WITHOUT the Hats on.

They should DESCEND while the Diaphragm regulates them as Air is allowed back into them ... when covered.

When Covered, ... the Diaphragm is purged when the Piston rises.
It's descent should be regulated by the Air returning into the Diaphragm's chamber.

In other words, ... a slight resistance.

 

okay I like that description and describes my situation. they are good then.

barely made it to work however. i was fighting a fuel consumption issue. if I left it on the "On" position, after a mile or so the carbs would surge and it was starving of fuel. so I'd switch it to the "Prime" position. came back alive. even noticed this at a couple stoplights whenever the bike would come to a stall and run out of fuel.

looks like I gotta work on the petcock and/or fuel levels? even if one float level is too low could this be an effect?

 

Yes, and only maybe. But double-check the vacuum line from #3 to the back of the petcock first. If it was a float putting it on PRI shouldn't "fix" it.

 

well the vacuum line is on #1 but that don't matter.

pulled it off the air nipple to #1, pulled the gas line off the tank, sucked on the vacuum line and gas comes out. verified petcock is working.

*stood there thinking wtf*

hooked lines back up; turned over the engine and let it run for a couple minutes like normal leaving petcock in the "On" position. notta single issue and ran just fine warming up. I did notice that the gas tank had very low fuel level and sniffed my oil. no gas smell from the oil resevoir so I know its not leaking down there because the oil is fresh from last nights' oil change. a gas station to refuel is a must and I will update what happens on the 40 mile route home this afternoon

when I checked float levels using clear tube last night (one last time), there was only one that was just a tiny tiny bit lower than the other three levels. didn't bother

I say sheepishly. All I did to the carbs last night was a bench sync which got me in running condition. Didn't even hook up manometers because it seems like I never get any progress once I start touching the damn sync screws.

 

If you have an Inline Filter, ... check it.
Blow through the Filter and make sure its letting enough gas flow to the carbs.

 

Is it REAL vacuum line? If it's just "hose" it could be collapsing in on itself once hot and getting vacuum.

 

It was too low on fuel.

So I pose a question.... Does "Prime" draw from the main holding fuel tank level only or does it also supply fuel all the way to "Reserve" fuel level?

I drove home today 40 some miles without switching it from the "On" position so it obviously had to do with the amount of fuel I had this morning. I should also note that it took 4.08 gallons to fill the tank. Which is a LOT for a 650cc tank... :? :?: In the 3 years owning the bike I've never put that much in at one time

Along the way home I stopped a few times along the country road (lucky for me to live in western rural Ohio) and made numerous adjustments to the main idle adjustment rod. Majority of the time I was turning the idle down. Finally I got it to when I pulled the clutch at 55mph the idle would drop rather than go up. However, at this point if I pulled to a stopsign and sat there for a minute the idle would go all the way to dropping dead on me. But the slightest turn in to keep it alive and another mile down the road it would most likely begin to race whenever pulling the clutch in.

At this point I think fine tuning is where it will set the proper idle.

Remember, I haven't touched the sync screws since a bench sync last night so I still have the process of running a vac-sync and ColorTuning yet. however, i'm scared to touch the sync screws I've rarely had success getting them balanced using the manometers for whatever reason

 

That racing is air getting in somewhere.

 

well when you do get around to doing the running sync, a quarter turn is a mile, sometimes i can see a difference just putting the weight of the screwdriver on the screw so easy does it.
maybe mark the screw heads so you can come back to where you are now if things start going bad

 

Bingo. We've had this discussion before. I think you're still "over-adjusting" like Mr. P said, 1/4 turn is enough to pooch the whole program.

TWEAK as in "nudge." Blip. Nudge. Blip.

You'll need to vac sync to get it to completely behave at idle, no matter how good the bench sync is. Bench sync is to get it running. It is. Vacuum sync it, and GO EASY. And be sure a fan is blowing on it.

Re: Your petcock question: PRI actually draws through the RES side of the in-tank filter. That filter/screen/tower thing is the only difference between main and reserve. The "main" side incorporates a standpipe, leaving some fuel inaccessible. "RES" on the other hand, allows fuel to draw all the way from the bottom. PRI simply routes that side of the input past the vacuum valve. Petcock tech: http://xjbikes.com/Forums/viewtopic/t=25058.html

 

Go back to START.
Do Not Pass GO.
Do Not Collect $200.

What you really need to do, ... is get the Bike to IDLE, on it own, with the Throttles Closed.
Do the rest of the tuning after the Bike is set to Idle.

You need to Adjust the Pilot Mixtures.
This is where a ColorTune comes in handy.
I'd loan you mine, ... but, its already borrowed!