Misfire & Hesitation

[oilheadron]

I don't think this is likely to be the problem, but have you tried spraying WD-40 or something similar on both sides of the #2 carb holder while the bike is idling to see if the idle speed changes? A change indicates a vacuum leak (I believe that #2 is running lean for whatever reason, probably due to some well-ridden gunk in the carb like Dave said, but it wouldn't hurt to check the carb holder too, and it's easy!). It isn't a bad idea to check all 6 while you're at it, one at a time of course.

Another remote possibility, are you sure that none of the idle mixture screw tips are broken off in the carb bodies?? My '79 had one broken off in #2 and had some similar symptoms to yours (except that the #2 pipe was cooler at idle; not sure about after a long run).

Also, are you certain that all 6 cylinders are firing at idle?

Some other variables: Have you had the needles out of the slides, and are all the spacers/etc. installed in the correct order? A low needle in #2 could very possibly cause these problems. Does it have adjustable aftermarket needles? If so, clips in the same position on all 6?? Are all the various jets the same in all the carbs?? Any evidence of drilling?

I'm on a roll now (but I'm probably reposting some stuff that 2 or 3 guys have already mentioned)!! Are all the float levels spot on?

REALLY grasping at straws now: Do all of the carbs have washers under their synch hole blankoff screws (or whatever they're properly called)??

[daves79x]

Ross:
Describe what you mean by 'air jets' and 'idle jets'. Did you remove the pressed-in idle jets? What jets are you going to replace? I'm as sure as I can be that your problem is some pretty plugged-up low-speed circuitry.

Dave

[ajs350]

I don't think this is likely to be the problem, but have you tried spraying WD-40 or something similar on both sides of the #2 carb holder while the bike is idling to see if the idle speed changes? A change indicates a vacuum leak (I believe that #2 is running lean for whatever reason, probably due to some well-ridden gunk in the carb like Dave said, but it wouldn't hurt to check the carb holder too, and it's easy!). It isn't a bad idea to check all 6 while you're at it, one at a time of course.

I have tried spraying the boots but no change in idle speed. The boots were replaced when I took the carbs off a few weeks ago so are now new.

Another remote possibility, are you sure that none of the idle mixture screw tips are broken off in the carb bodies?? My '79 had one broken off in #2 and had some similar symptoms to yours (except that the #2 pipe was cooler at idle; not sure about after a long run).

All the mixture screw tips looked good when I had them out. They were all certainly the same.

Also, are you certain that all 6 cylinders are firing at idle?

Good question which I cannot answer. I think they are but how would I know if one is not firing?

Some other variables: Have you had the needles out of the slides, and are all the spacers/etc. installed in the correct order? A low needle in #2 could very possibly cause these problems. Does it have adjustable aftermarket needles? If so, clips in the same position on all 6?? Are all the various jets the same in all the carbs?? Any evidence of drilling?

I had the needles out and they are of the fixed length variety so I assume they are original. The sequence if I remember right was that the needle dropped into the slide first followed by the aluminum screw. On top of this was a rubber stopper with an o-ring round the outside. I do no recall any spacers.
115 main jets were replaced with 110's and the #35 idle jets were removed for cleaning although they looked perfectly clean. None of the crud you typically see. No drilling evident either.

I'm on a roll now (but I'm probably reposting some stuff that 2 or 3 guys have already mentioned)!! Are all the float levels spot on?

I sprang for the float level tool from Tims and set all float heights as per Mike Nixons book at 15.5mm.

REALLY grasping at straws now: Do all of the carbs have washers under their synch hole blankoff screws (or whatever they're properly called)??

All have the washer in place although I did not check to see how petcock vacumm tube fits into carb #3.

[ajs350]

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[ajs350]

Ross:
Describe what you mean by 'air jets' and 'idle jets'. Did you remove the pressed-in idle jets? What jets are you going to replace? I'm as sure as I can be that your problem is some pretty plugged-up low-speed circuitry.

Dave

Dave, the idle jets being the #35's which are pressed in and need to be tapped to pull out. The air jets are the little brass fittings at the top of the carb on 2 through 6 and behind the air cut off valve cover on #1.
Having checked the idle jets thoroughly I figured the air jets were somethig I had not touched and worth a look. I'm kind of with you in that it would point to some blockage in the low speed circuitry even though I blasted 5 cans of carb cleaner through them! As I am about to cover old ground what can I do that is different to clear these passages? Ross

[oilheadron]

Pull and then replace one sparkplug cap at a time while the engine is at a fast idle, say 2k (you might want to wear some heavy gloves unless you enjoy shocking revelations :) ). If the drop in idle speed for any particular cylinder is significantly less than the others, or maybe even not noticeable at all, bingo! Problem cylinder identified. Some may fear that this could possibly damage the electronic ignition, but we've never seen that happen.

P.S. Have you run a very fine guitar string through all of the accessible passages?? Or blown compressed air through them so that you can verify that all 6 carbs have passages open to the same degree?? What kind of carb cleaner are/were you using?? Some of them on the market these days are totally useless (Mike N's carb manuals tell you how to identify the good ones).

Have you prayed to the carburetor gods lately?? Let's not leave any stone unturned here.

[ajs350]

Pull and then replace one sparkplug cap at a time while the engine is at a fast idle, say 2k (you might want to wear some heavy gloves unless you enjoy shocking revelations :) ). If the drop in idle speed for any particular cylinder is significantly less than the others, or maybe even not noticeable at all, bingo! Problem cylinder identified. Some may fear that this could possibly damage the electronic ignition, but we've never seen that happen.

P.S. Have you run a very fine guitar string through all of the accessible passages?? Or blown compressed air through them so that you can verify that all 6 carbs have passages open to the same degree?? What kind of carb cleaner are/were you using?? Some of them on the market these days are totally useless (Mike N's carb manuals tell you how to identify the good ones).

Have you prayed to the carburetor gods lately?? Let's not leave any stone unturned here.

Ron
I removed each plug cap but did not find a noticable difference in idle for any of the 6. I guess that means they are all firing?

I did not push through a guitar string as the carb cleaner came spurting out of the different orifices noted in Mike's book. A mistake I think. I will get some string and work it through when I take the carbs off.

I have prayed to the gods but they are not listening. Maybe a sacrifice is required.

Ross

[oilheadron]

Burn a Harley. That ought to do it. :)

[Jeff Bennetts]

Ross, since you're pulling the carbs again to clean them go ahead and clean the stripped carb set in very hot soapy water, I use Marine Clean made by Por-15 but you cant let them soak more than an hour or so or the solution will begin to turn the aluminum carb bodies a gray color.

Whenever I clean a set of carbs I always clean them at least three sometimes four times, once to get the external grime off, a second in hot soapy water and again with the carb cleaner (Berrymans). As mention above I use electric guitar strings to chase every passage possible then finish with compressed air and then double check that the passages are clean by spraying the carb cleaner again and verifying the carb cleaner exits all passages and orifices.

I also made a cheapo sonic cleaner for about $12.00 that works great at cleaning the carbs internally and externally while using the hot soapy water. The reason the hot soapy cleaning is necessary is because sometimes calcium deposits will plug the carbs from water being in the fuel system and petroleum based solvents will not dissolve them.

Heres a pic of the sonic tub

[steve murdoch icoa #5322]

Jeff, knowing how frustrating the carbs can be at times i can see why a hand gun might be required to keep the bandits away from your clean carbs .

[CopperCollar]

Ross, I be facing the same issues when it comes to these carbs. I have wrenched on bikes for many years but the carbs on the CBX threw me for a loop.

I rebuilt the carbs, got them damn clean and the bike fired right up. She wouldn't run for shite below 4k and seemed fuel starved. I pulled the carbs off and this time I threaded the pressed in idle jets and pulled them out. I found 3 of the six clogged solid, the other three were partially clogged. I thought I had done a good job of clearing them. guess my .013 wire really did not go through them.

The clogged jets would not open, not with a week in Berrymans nor the application of heat. I gave up and ordered a set from sirrus....two week shipping time with Canadian customs and air mail...go figure.

In the mean time I cleaned the old ones out but it took the cutting torch tip cleaner, not bad but the tip cleaner is a 0.015, not the 0.013....so I can't use them, it may be to rich for the bike.

Mike

[ajs350]

Thanks for all of the suggestions. I have idle jets ordered from Sirius which might get here late next week. So in the mean time I'll be collecting all the required chemicals and guitar strings to take another crack at the carbs. I'll let you know how I get on. Thanks again. The help on this site is amazing. Ross.

[ajs350]

Carbs are off and I have pushed a guitar string through the idle circuit from the air bleed at the top through the idle jet orifice at the bottom. I've blasted Berrymans B12 through all orifices and if I squirt it through the air bleed while holding 2 fingers over the idle and mixture holes I get cleaner blasting out of the 4 holes in the venturi. Accelerator pump is working fine also.
I removed the idle jets but to be honest they look the same as the new ones I bought. I wish I had found something specific that would give an "Ah ha" moment but no luck.
Not sure I have done anything to make # 2 run cooler or eliminate the stuttering and hestiation below 4K.
Any other suggestions before I put it all back together?
Thanks Ross

[oilheadron]

When you press the CV slides up and then let them return do they all feel about the same? No sticking?? Sometimes their edges can get dinged and cause drag in the bores. Are the slide bumper rings installed correctly (with the ridges facing upward if I remember right)?

[ajs350]

When you press the CV slides up and then let them return do they all feel about the same? No sticking?? Sometimes their edges can get dinged and cause drag in the bores. Are the slide bumper rings installed correctly (with the ridges facing upward if I remember right)?

Ron - thanks for the new idea.
All the slides move freely up and down. The slide bumpers are pressed in with the round edge and o-ring first.
Ross