Carb problems again ......, and again ........, and

Reinstalled carbs after pulling, cleaning and inspecting for 3rd time. Struggling. Vacuum test good, color tune good except for #1 cylinder (cannot get it to change color regardless of fuel mixture needle setting). It's running rich, getting excess fuel from somewhere obviously (plug soots up as would be expected). float bows right-on.

Starts to run rough at higher rpm's in lower gears, in 4th and 5th and excelleration struggle getting it to 5K rpm.

My thoughts: gonna get new vacuum caps, again recheck valve clearance (rechecked twice in last 200 miles), check fuel enrichment circuit needle for scratches, maybe get new (used) carb body. Re-check compression.

Any nuggets or insight for problem?

becoming disheartened.

 

dm,

Set your mixture screws at 2.5 turns out so you will know it's not running too lean. Take it for a 20min ride then start color tuning. The ride will bring your bike to full operating temperature and burn condensation which will give a more accurate read while color tuning. Hope this helps.

Roc

 

I had this problem with the #4 cylinder. Mine was a cut (and hence, leaking) throttle shaft seal.

Other things:
Did you check the diaphragm for #1?
How far did you try adjusting #1 in?
How did you clean the carbs?
How far did you tear down the rack?
Did you remove the jet under the cover that is under the carb hat?
Change the plugs?
Charge the battery?

 

If you're sure you got the valves in spec, don't bother re-checking them every couple hundred miles, they don't change that quickly. Same for the compression; if you're getting good numbers, move on; the motor didn't suddenly change on you.

The problem lies elsewhere; most likely still plugged primary air circuits in the carb, or the enrichment plunger isn't shutting off fully, or a float is acting up on you.

 

Thanks all for thoughts. Set fuel misture at 2.5 turns out for lack of any other reference. *pulled and disasembled all carb bodies & used Chacal deluxe rebuild kit. *used lots of carb cleaner, copressed air and brushes to clean bodies. *replaced one carb body (#2). *plugs / battery all new. *ensured upper air jets were clean and in appropriate place. Not sure what a trottle shaft seal is?

*floats calibrated and rignt on the mark. Leaves me with enrichment needle problem and/or plugged air circuit. I guess this means remove again and what? OR, just buy a new/used #1 carb body?

Was going to look at compression and valve clearance just to rule it out as the bide is down and out anyway.

Thanks again all and more comments welcome!

 

What color is the colortune showing on the #1 cylinder? If it's orange all the time (regardless of mixture screw setting), then it is a rich condition, and either the floats are way too high, the enrichment circuit is leaking (see if physically pushing down on that plunger remedies the problem), or something is amiss in the jetting in that carb (pilot fuel jet is too large, or pilot and main AIR jets reversed). A final problem could be that the main jet needle/vac piston is not setting down to its fully closed position.

 

It's a whitish / faint orange regardless of mixture screw setting, and it is definately rich as plug is sooted up real fast.

The two main air jets (top of carb) were double checked, to make sure numbered correctly and in proper hole. Not sure about pilot fuel jet being too large but bike ran fine prior to removing carbs the first time, I'm using that to say all jets are proper for the carbs ........ other than that, I'm clueless and could be quite wrong.

The main jet needle /vac piston cleaned/polished and clunk tested real well but could be issue .... not sure how to tell.

Thanks for the hint about enrichment circuit, I'll test to see if there is slop and It's not going all the way down. I've a high degree of confidence on floats at proper heights.

I'll play a bit more with it on the bike and checkout the enrichment, if not seeming to be an issue I'll pull carbs again to dismantle #1.

thanks again for you continued troublshooting guidance.

 

Hate to tell you this but I had the same problem and the answer I found that the carbs just weren't cleaned good enough. You have to have every little passage cleaned out.

 

Well, white on the colortune is an extremely LEAN mixture, and an overly lean mixture can also cause an engine to be seemingly running rich....see the part in red further below:

RICH, LEAN, or possibly even ritually UNCLEAN or OBSCENE: THE CARB REBUILDING FAQ:

Let us begin by warning you, though: an engine that is out of synch may perform AS IF it has a lean, or a rich, or a hanging idle, or a no-idle, or a run-away idle, or any variety of different conditions------if your engine (carbs) have not been synched, then that at is the #1 issue that you should attend to first, before you even READ any of the guidelines below and go and try to adjust and fiddle with things and change settings THAT AREN'T THE CAUSE OF THE REAL PROBLEM!!


Question #1: Why Isn't It Running Right?:

Below is a semi-useful "general rules-of-thumb" list to help you recognize and diagnose fuel-mixture problems.

All of these descriptions assume that the carburetors are cleaned and operating properly, are stock (no jet kit), the valves are adjusted properly, and the engine has been synched.

If any of the above procedures, tasks, actions, or activities have NOT been checked or performed, then do them first, or otherwise all your other efforts will barely even give you "casino odds" at striking it rich and determining what the real cause(s) of your symptoms are......



Typical Symptoms of a Lean Fuel-Mixture Condition:

- Poor acceleration; the engine feels flat.

- The engine won't respond when the throttle is snapped open, but it picks up speed as the throttle is closed. (A too-large main jet also mimics this symptom.)

- Idle speed falls after you blip the throttle, then creeps back up.

- The engine runs hot, knocks, pings and overheats.

- A lean pilot circuit condition can be responsible for a creeping or hanging high idle, where the rpms stay high then slowly drop down to the set point.

- The engine surges or hunts when cruising at part-throttle.

- Popping or spitting through the carb occurs when the throttle is opened. Or popping and spitting occurs through the pipe on deceleration with a closed throttle.

- The engine runs better in warm weather, worse in cool.

- Performance gets worse when the air filter is removed.

- Fuel levels that are too low will cause a lean condition.

- In cases where an overly lean fuel condition is suspected, the application of a small amount of "choke" may decrease or eliminate the symptoms.



Typical Symptoms of a Rich Fuel-Mixture Condition:

- Engine acceleration is flat and uneven and loses that "crisp" feel.

- The engine "eight-strokes" as it loads up and skips combustion cycles.

- The engine's idle is rough or lumpy, and the engine won't return to idle without "blipping" the throttle.

- An overly rich pilot mixture is usually the culprit when the idle drops low then slowly recovers.

- The throttle needs to be open continuously to maintain acceleration.

- Black, sooty plugs, a sooty exhaust pipe and black smoke from the tailpipe that stinks of unburned fuel.

- Poor fuel economy.

- The engine works better when cold. Performance falls off as it warms up or the ambient temperature rises.

- Engine performance improves when the air cleaner is removed.

- Fuel levels that are too high will cause a rich condition, as will a choke system that is slightly hung open or has leaky plunger valves.




Some common causes of a high idle:

- A lean air-fuel mixture condition, which can be caused by a variety of problems......vacuum leaks, plugged or too-small fuel jets, etc. Old or "stale" gas may also cause a lean fuel-air mixture to occur temporarily (until the fuel is used up!).

- A vacuum leak somewhere in the intake system.....intake boots, internal o-ring seals, etc.

- Mixture screws not properly set or adjusted.

- Vacuum piston sticking or stuck in a partially raised position.

- Idle speed screw set too high, or set to create a "proper" idle speed when the engine was cold (and thus results in a "high idle" once the engine reaches operating temps). The idle speed when the engine is cold should be modulated via the use of the choke (enrichment) control system.

- Butterfly valves opened too far; synch screws out of adjustment.

- Throttle cable wear, adjustment, or throttle lever brackets installed incorrectly or interfering with other nearby objects (cylinder head fins, etc.).

- Choke (enrichment) circuit is stuck "open"....this can occur even if the choke lever is rotated to the fully closed position, if for some reasons the choke plungers are not fully closing (cable wear, cable adjustment, bent finger brackets, or installation problems). In addition, even if the choke plungers are "closing" fully, if the choke plunger valve face or its seat are worn or scarred, this will allow fuel to leak part the plunger and richen the mixture even if the plungers are closed.



Why your engine seems to be schizoid:

A hanging idle---one that stays high and slowly comes down when decelerating---is a sign of lean mixture. The opposite case, where the idle drops dangerously low then rises, is a sign of rich mixture.

A bike that runs better when hot is probably lean, and a bike that runs better when cold is probably rich.

But sometimes a bike that can be adjusted "just right" when cool, but actually starts exhibiting signs of running lean (hanging idle) as it warms up. And if the idle speed is then re-adjusted while the engine is warm, but eventually falls and the bike dies (especially when sitting at a stop light). Or if the pilot screws are adjusted, then it's too rich when cold---all in direct contradiction of the above observations.

Experience shows that this is a sign of worn throttle shaft seals.....the aluminum carb bodies expand with the heat, but the steel throttle shafts---resting comfortably in a nice cool airflow---don't heat up and therefore don't expand. Once the shaft seals get old and hard, they no longer are able to flex and fill the gap.....so the carb starts drawing air around the shafts, leaning it out.



Why does my engine sometimes backfire when I first turn on the key (without attempting to start the engine)?:

- When you kill the engine, the intakes will still have some remaining (un-burned) air-fuel mixture remaining in them. Upon powering up the bike (turning the key on), the ignition system will apply 12 volts to the coils, thus charging them. Of course, that constant current is not good for the coils, so few seconds later (if the engine is not started) the TCI shuts down the coils by grounding them (to protect the coils from overheating) which cuts the current to the coils and thus triggers a spark to the plugs. If there is enough un-burned fuel in the intake manifolds or the combustion chambers, and if the valves are held open by the camshafts, a backfire thru the exhaust header and/or thru the intake manifolds/carbs/airbox can result.



Why are my plugs carbon-fouled (dry, sooty black deposits)?:

- Carbon fouling is the result of incomplete combustion----for any reason. It is most often associated with an overly rich fuel mixture (whatever the cause), but can also be caused by an overly lean fuel mixture (or poor spark, etc.) In a lean-mixture condition, most of the un-burnt mixture gets pumped out the tailpipe, but some fuel droplets remain in the cylinder and add themselves to the next intake charge. That's not a very precise way of metering the mixture, so when it's finally rich enough for a spark to ignite, that particular charge may be too rich, resulting in incomplete combustion and plug fouling. So carbon-fouled plugs can be due to rich or lean conditions.......your Colortune spark plug will tell you for sure. If you have a light blue or white-ish flame, intermittent flame, and/or intermittent flashes of yellow/orange within an otherwise white-ish flame, then your fuel mixture is too lean.

And by the way.........if the spark that happens to ignite this overly-rich mixture is the "wasted spark" (which occurs in each cylinder at the top of the exhaust stroke, it will occur JUST AS THE INTAKE VALVE IS OPENING ---- so the backfire pressure wave may be directed back up the intake tract!

 

Okay, quite possible it's lean as I'm mostly clueless. For the sake of argument, what line of attack do I now take?

 

Check heat of each header after first starting. That wiill at least narrow it down to the offending cylinder(s)

 

yep .... #1's the issue. what to do.

 

We had that issue at a carb clinic one time......turned out the jet was laying in the bottom of the bowl......had somehow fallen off.

If you don't know what a throttle shaft seal is, then you didn't do a COMPLETE rebuild. Those require the whole rack to be taken apart, and then each carb body taken completely apart.....the butterfly comes off, and the shaf that it it attached to..........the throttle shaft.......has to come out. There are two seals on each one.

THAT being said, you indicate you're running rich...which would NOT be a symptom of throttle shaft seals--if they leak you get a lean condition.

Personally, from what I've read, I'd pull the idle screw out and check to see if you forgot to put the o-ring in, or put the washer in first......sounds like too much fuel is still going through the mixture screw.

Dave F

 

Just confused by the nomenclature. rack completely disasembled and used Chacal deluxe kit for rebuild. Unless some jets that are not supplied in the kit are the issue, i'm still at a loss.

Just recently pulled #1 carb off the rack to recheck all parts clean. Chacal thought it may be running lean caused by air leak ...... checking that posibility too by insuring all seals are re-lubed. did not find any engine race when useing propane test during idle.

just seems strange that it would be lean when I find the plug wet. Oh well, put the rack back on and hope I don't need to pull it again.

Thanks for thoughts.

 

don't worry, pulling the rack will go from a stick in the eye to a hammer on your thumb to a weekend at the in-laws, in no time

 

well stated!

 

Disassembled as in took the butterflies out of the carbs and pulled out the shaft that they screw into and replaced those two seals in each carb?

(There are different "deluxe" rebuild kits.)

You're absolutely sure you didn't transpose the position of the two jets under the diaphragm?

 

Yes indeed bigfitz .... Just finished pulling them apart again and lubed seales just to be sure. Also checked and double checked placement of the two jets under diaphragm.

I just posted another plea for help on the forum .... see if any of that discussion help with dianosis.

Carbs gotta come off again I suppose.

 

Yeah, I saw the new thread. Why? We've been hammering on it here; were you expecting any different answers?

 

So......if I have this straight:

All indications are that it's too RICH, while everyone else seems to be pushing that it's too LEAN.

SO: I'm trying to get this straight--

You've said:

your plug is too sooty-

That would indicate that it DID have too much fuel, but burned it all up and is now dry.

Your plug is wet -

That would indicate that the plug DOES have too much fuel and is NOT burning it all up

Your plug fires strong in the air -

That would indicate that the plug is firing in the air, but not necessarily in the cylinder. BUT, if the plug is dry and sooty, it has to be firing long enough to burn whatever gas does get there.

SO------I want to know three things:

1. Have you simply tried a new sparkplug?

2. (and here's the biggie) TELL US YOUR VALVE CLEARANCES. Why?!? You need three things: Spark (you theoretically have), fuel (you theoretically have......maybe), compression (we don't know if you have it or not..............a valve hanging open will cause compression loss).

3. Did you check that the tube going IN to carb #1 is clean and clear? I've had several racks come through where one of more of the connecting tubes were clogged......

Let us know that, too.......................

If nothing else, we eliminate issues until the right one becomes clear.

dave

 

Are your valves in spec, and your fuel height wet-set properly?

 

Actualy big fitz, I was hoping to see/hear someting new based on my most recent observation.

float bow in spec.

*1 Brand new out of the box plub (today), old plug had maybe 50 miles at best.
*2 valve clearance for #1 is: EXH .17mm -- INT .11mm
with uncalibrated compression guage ..... 125 across the board (calibrated guage read 150 psi last year)
*3 I'm not sure what you mean by 'tube' into #1 means. I've cleaned and pushed compressed air through all orifaces. If you can clarify 'tube' for me I will try to let you know wheather I specifically cleaned that or not.

Bigfitz - I'm not trying to be a smart-ass here, just trying to figure it out. I've done exactly the same things to 2,3,4 and only #1 is unresponsive.

I originally thought it was rich, chacal thought lean, recleaned and now no fuel showing at all .... I need any thoughts on how to fix #1 to match 2,3,4. I'm at the point of buying a new #1 carb and all internal jets ..... Just seems crazy as it was purrrring prior to carb rack removal and rebuild. (original problem was stuck float and leaking fuel on #1)

Now I have no leak after rebuild but cannot get fuel to cylinder, Previosly has carbon buildup on plug .... nothing stays the same except on #2,3,4.

Just crying here. Please help ..... If no other suggestions I need to buy a new carb body and all internal jets that have not yet been suppied in Chacal's kit.

 

Ok......so now it's not gettting any fuel at all to that carb. So..... NOW it's a lean condition. Lean to the point of non-existent. Since no fuel is showing at all, then that clearly indicates a blockage of some point.

Either:

the T is plugged on that side
the passage from the side of the carb body to the fuel needle is plugged
the needle itself is stuck shut
the float is holding the needle shut

If the T, and the passage is clear, then that still points to float or needle

Just because the float is new, does not mean it's in spec. You must check the height of the floats. Ideally, a dry setting will result in a correct wet-set, but you should check them wet, anyway, that will tell you a lot.

If the float sits to low in the bowl (in running position) the fuel will make the float close the valve before enough fuel fills the bowl. If the float sits too high in the bowl (in running position) the fuel will overflow as the float will be unable to close the fuel needle properly.

If the float is correct, and fuel still gets held up AT the needle, you may have to get a new needle ( the rubber tips can get sticky).....I'd recommend getting the all-metal ones..............or you may need to polish the 'seat' inside the fuel valve. Use a drop of polishing compound on the tip of a golf tee, spinning it back and forth in your fingers til shiny and smooth.

However, with fuel not getting into the bowl to begin with, you theoretically can't do a wet set..

BUT........here's the question--- When you pull the carb apart, IS THE INSIDE OF THE BOWL WET OR DRY?

If the bowl is wet, then we know the issue is from the float needle the cylinder. If the bowl ITSELF is dry then we know the issue is from the float needle on back.............

So, simple-----tell us if the bowl itself is dry or wet
dry= needle is shut or passage is clogged
wet = problem is at or after the float valve

dave

 

Hold on.

We've discussed "wet-setting" the floats a number of times and the answer has always been "done it."

However; if you had WET-SET carb #1 you would have known right then that there is a fuel delivery issue.

Pull the rack, set it up level, and properly wet-set the floats. Any fuel delivery issues will immediately reveal themselves in the process and make it much easier to diagnose.

 

I'm just not seeing where a float-height setting has actually been done. All I keep seeing is that the floats are new. Heck, a new float can even be upside down.

 

float bowl has fuel and has been wet set .... painfully so. Even checked it while installed to make sure nothing had changed using carb bowl drain.

However, this morning, still frustrated, I decided to take it off the center stand and crank it over. Hmmmmm ... now I'm getting fuel on the spark plug. Yesterday it was bone dry (on center stand and even running with enrichment circuit open).

Today I have fuel on plug along with small amount of wet black soot. It seems to be ocassionally firing (but obviously running rough). Exhaust pipe only 25% to 50% temperature of other three. Wifey found out the hard way .... don't grap hot functional exhaust to compare temperature. It even hurt me just looking at her hand.

Does any of this make sense or help with diagnosis and a plan forward?

 

Where was your fuel level when you did the wet-set?

 

Bench wet set at 3mm (+/-) 1mm. At least as well as I can eyeball it with these old eyes. (measured from lowest point on carb body)

All other float bowls set the same and seem to function fine.

 

Okay, don't know what else to do except remove rack and completely go through #1 carb body again. ...... However, prior to doing this, IS there anything I can do to help with diagnosis while the carbs are still on the bike?

What am I currently thinking ..... *buy new carb body to eliminate that possibility. *Somehow ensure valves are functioning properly (they are in spec).

Thanks for everyones help to date.

 

I don't think you need a new carb body.

Also, if your compression values are good, then you know the valves are working.

 

Okay, thanks. With an old uncalibrated compression guage I get 125psi scross the boad ...... so I'm gonna say 'no issue'. So it's carb cleaner and compressed air.

Here we go. thanks

 

a word about that compressor. i blew a o-ring from the pilot screw back into the carb passage once, 90 psi don't mess around.
the brake cleaner didn't seem to go through that carb like the others. if there wasn't others to compare it to, it seemed ok and clear

 

pilot screw o-ring there after last compression check, but I'll look again. Thanks.

 

separating # 1 carb body from rack again. Thining about boiling and or ultrasonic bath ..... probably both. Recommendations on solutions for the soak and or boil?

 

So ... pulled carb rack and separated #1. Fully disassembled. Here is my plan: Ultrasonic cleaner using carb cleaner. Any thoughts on this medium for the ultrasonic? If this is a likely approach, how much time would be best.

Again, if this is a good approach, what other parts should be done at the same time. I'm doing carb body and fuel float bowl.

Upon disassembly all pasages look clear. Light goes through small holes just fine. Thin wire throiugh the copper enrichment circuit post without restrictions.

Any thoughts appreciated.

 

WOW - no opinions? On the verge of starting the ultrasonic.

Is this a good idea or a waste of time?

If it's a bad idea and possibly make my situation worse, I will not go down this road.

I need support one way or the other! Help.

 

It can't hurt, but it may not help.....much. Typical "home-use" ultrasonic machines have nowhere near enough energy output to create the tiny bubbles that would be needed to penetrate inside the fuel passages fully....and it's inside those tiny passages where the built up fuel varnish is hiding.

Best method is to soak overnight in a suitable solvent (i.e. Berryman's B12 carb dip) and then blast away with aerosol carb or brake cleaner until every passage is clean and flowing fully (you'll know it when it is), along with compressed air. Depending on how gummed up the passages are, in make take a couple of repeats to get them "zestfully clean".

http://www.xj4ever.com/inside%20your%20carbs.pdf

 

There you go. I tried to post the link to that PDF the other night and couldn't find it. Gives you a good map of the battle you're fighting.

Len mentioned Berryman's B12 Carb Dip. Great stuff; don't leave 'em in too long. I'd like to add that Berryman's B12 Chemtool aerosol carb cleaner far outperforms all others. But be UBER careful with it; it will melt any form of plastic/vinyl/paint, anything it touches that isn't metal.

 

The bad news is that I had to get it started this morning. I used the NAPA brand carb cleaner.

The good new is that the ultrasonic I used is industrial grade and heated. Cooked it for 2.5 hours.

Since I've gotten this far I believe I'll pass on Barrymans unless you think it is still a good idea.

I'll confirm all passages are open with compressed air and start my reassembly.

Thanks for responding. At least now I don't believe I've made it worse.

 

I'd buy a can of Berryman's B12 Chemtool for the aerosol and quit screwing around with store brands.

It really is "head and shoulders" above the rest. In my neck o'the woods, AutoZone has it. Not cheap, but it works when others will not. I only use it for carbs or when I have to bring in the artillery, use the other stuff for everything else.

Check out the PDF Len posted the link to. I wasn't kidding.

 

Thanks I'll try again .... Didn't think NAPA was all that cheap, so I cannot wait to see Berrymans sticker price.

So a bit confused ..... should I soak over night or, don't leave 'em in too long (not sure what too long is).

Should I use ultra sonic heated bath or just room temperature with the Berrymans?

thanks guys ..... still dont want to ruin anything. Although at this rate a new carb body may have been less expensive.

 

We're talking about two different products here.

Berryman's makes a carb dip (my preferred) which comes in a gallon can.

They also make an aerosol called "Chemtool" also in the "B-12" line.

Different stuff. I wasn't advocating you switch your dip of choice; just that the follow-up flushing and spraying out of passages be done using their aerosol. I think the last time I bought a can it was $12. Not cheap especially if store-brand aerosol is $4 a can; which is why I don't waste it in general shop use.

Don't run out and buy a different dip; just use the "good stuff" to blast those passages clean. And WEAR SAFETY GLASSES I learned this the hard way; I'm old school so I never do ("real men" and all that) BUT DO IT. I learned the meaning of "a world of pain" with but a droplet.

 

Sorry missed a couple of questions.

"Overnight" varies depending on many factors; I take it to mean 6 ~8 hours.

LOOK at them after about 6 hours; if they're beginning to darken, pull them.

The brass parts will go from cruddy to clean to darkening. Pull them at "clean."

Can't help you on the ultrasonic, I'm not that high-tech.

Last but not least, you won't make anything worse by cleaning it. You might even win. Did you look at the cross-sectioned carb yet? It's a wonder any of us pull it off.

 

Yes, I did see the link Len sent and was going to mention that but lost my thought train while composing.

Going to be tough to tell when the brass looks clean, as today's bath already made them look clean .... at least to me.

Indeed, amazing these things work at all with all the tiny passages to get clogged. Sure hope this solves my issue but I'm still not totally sure this is my issue.

I don't have enough experience with these carbs to have confidence.

 

Thanks - the Berrymans Chemtool arisol sounds like a good approach. I was thinking the Berrymans dip gallon would be $50 or more.

I'll look for some tomorrow morning and shoot the crap out of it.

thanks again

 

Don't overlook that Berryman's will eat up rubber parts (i.e the throttle shaft seals)..............

 

This is a inexpensive tool to have when cleaning the carb passages..

http://www.homedepot.com/p/Lincoln-Elec ... /100341101

It worked for me on two different racks....

hope this helps

 

You'll know what clean brass looks like. It looks like almost new. If you leave it in too long, starts to get a reddish hue....but that buffs off, too, just takes a little extra work now.

I leave stuff in the can for a day, or overnight, I've had some times where it may be in for a couple Of days......
Dave

 

Hello out there. Any body know if the xj600 mikuni carbs would work on my 82 xj650? I keep cleaning and cleaning this hitachis and still not running right.

 

I guess you'll be the first to find out.....