Perplexing Problem - Part III

[Shuriken]

This thread is a continuation of the following threads, part I and II....
http://www.vmaxforum.net/search.php?searchid=83806

....

Bought an inductive light today - as an upgrade to my existing one - that has an RPM meter built in.

Warmed the bike up to operating temp, then clamped pickup to plug wire #1. Took the bike out. In first gear, with the trigger pulled, I accelerated as safely as I could, having only one hand on the bars. I could not see any drop out in strobe when the engine started to crap out.


The Max has 2 pickup coils. Can I assume that the following are in decent working order?

• #1 and #3 spark plug
• #1 and #3 lead wire
• #1 and #3 ignition coil
• pickup coil for #1 and #3

Since #1 and #3 are on the same pickup coil, I assume that repeating this test on lead wire #3 will produce the same result. That is of course, unless ASSuming is going to turn me into a fool...
I cannot test #2 and/or #4 with the light, tonight, because someone will probably call the cops on me due to the noise from my drilled mufflers....

If I do the same test on #2 and/or #4 coil(s) and don't conclusively see a lack of strobe, I'll have to assume that my carb rack is jacked up.

 

[maleko89]

I agree with your assumptions. My question is has anybody ever have an early model coil go out but only affect one cylinder? In my case, I dropped two cylinders as expected. I don't know, it might be worthwhile to test all four cylinders but would test #2 or #4 first.

I wish I still had a spare rack of carbs...I would mail those for you to try. If snow was flying here I'd mail you my carbs.

 

[dave741]

hi guys , i dont know if this will help but i worked at a gm dealer for a long time . many gm cars used one coil for every two cyl . i dont know if it relates but i can tell you 4sure that at least in cars half of your coil can go bad . but i dont think thats the problem your haven because coils work or they dont . coils do not stumble now and agin unless they are told to , meaning try testing the power sig befor the coil at the rpm and see if maybe something is telling the coil to stumble . my max is in the dealer getting the valves shimmed . it should be done thurs or fry , ill tell them the problem your haven and what you have done so far and see what they say .

 

[Neil-3446]

You've got a weak v-boost gasket maybe???

He'll pop and crack and sound like the meanest bitch ever, until I wonder about the valves....

Really, high end cracking is a lean condititon!!!

This one is almost 99% right. Notice the berp on the right hand side!

http://www.youtube.com/watch?v=57CV_522SbM

Neil

This bike runs sub 9's after 23 years, and sounds like shit!

8.57 on gas at 161.293 MPh

Nothing special!

 

[Shuriken]

hi guys , i dont know if this will help but i worked at a gm dealer for a long time . many gm cars used one coil for every two cyl . i dont know if it relates but i can tell you 4sure that at least in cars half of your coil can go bad . but i dont think thats the problem your haven because coils work or they dont . coils do not stumble now and agin unless they are told to , meaning try testing the power sig befor the coil at the rpm and see if maybe something is telling the coil to stumble . my max is in the dealer getting the valves shimmed . it should be done thurs or fry , ill tell them the problem your haven and what you have done so far and see what they say .

That's a good idea. Why not connect the voltmeter to the 12v wires feeding the coils? Then take the bike out and see if there is an input voltage problem..... that's another test I can do to help eliminate electrical as the culprit....

I'd be interested to know what the dealer says.

I'm leaning more and more in favor of a carb problem. But I can't for the life of me figure out what carb problems there would be. Unless I've missed something. I've cleaned and inspected them 3 times now, soon to be 4. Just not sure what could be going wrong if it is a carb issue.

I thought it would happen all over the range but it seems like now it's really only from mid through WOT. So this would bring the main jets, jet needles, vacuum diaphragms and springs into play.

If I can't find a spark issue, I'll yank the carbs yet again.

If I decided to replace/upgrade the carbs, what other years could I swap?

 

[Shuriken]

You've got a weak v-boost gasket maybe???

What do you mean, the o-rings under the v-boost manifolds?

I replaced the air intake boots, rubber v-boost boots, and also intake manifold boots and o-rings.

Also, this problem is not dependent upon engine RPM. It start crapping out long before VBoost should ever open up. If VBoost comes on based on engine RPM at say 6700, this problem starts before that, so I assume VBoost to not be a factor.

 

[Shuriken]

Okay.....

The other night I didn't operate the timing light correctly. Tonight I did.

What I found did not surprise me. The timing light indicates that the bike is getting good spark.

The only time the light would shut off was when I disconnected the inductive sensor from the spark plug lead and occasionally, on deceleration on only the front 2 cylinders.

I was not able to observe any loss of spark when the bike started to flub when I opened it up from mid to full throttle. I repeated this test on all 4 cylinders.

Therefore, I am concluding that whatever problem the bike has is a carb problem. I just can't see how it could be electrical.

The only strange thing I noticed is what I already said, which is that the spark seems to drop out for a few cycles on the front cylinders only when decelerating. This does not seem to happen on the rear cylinders. The front cylinders are fed by stock coils, caps, and lead wires. The rear cylinders are fed by stock coils and caps but with yellow aftermarket lead wires.

So.... now, what the hell is wrong with these carbs? I don't think I screwed them up. The bike would not idle or run very well when I bought it, so I removed them. I cleaned them with cleaner and compressed air, checked everything, reassembled, and then synched them. Then the bike ran pretty flawlessly for months. Then while riding straight and level on the interstate, I noticed all the sudden I had no VBoost, and the saga began.

The only thing I can think of is that the bike is getting a crap load of fuel on mid and full - too much to burn, hence the black smoke cloud, sputtering, etc.

Should I spend more money on rebuilding the carbs or should I just buy a a newer set?

If I stay with these carbs, I will need new bowl gaskets. I have smaller main jets to install. I plan on welding up the exhaust pipe holes to go back to stock.

What would be the result of leaking black rubber jet block plugs?

 

[maleko89]

If those rubber plugs leak then you'll run rich.

 

[Shuriken]

If those rubber plugs leak then you'll run rich.

That was my thinking, just verifying. How rich? What if there were no plugs at all? No run at all?

Trying to weigh getting a new/newer set of carbs or dump more cash into the ones I have...

 

[maleko89]

If it's the plug that goes over the pilot jet it'll run with or without. Some have put that plug in the far right tube that's blank and it ran. But that was only one carb. I'm not sure what would happen at idle if all four pilot plugs were off. Defiteily rich.

I think the middle plug would be worse since that covers the emulsion tube. This would affect running everywhere since all mixture goes through that at some point.

 

[maleko89]

One option is to mail me your carbs and I can put them on my bike. If I get the same symptoms we know it's the carbs. Then I can break 'em down and see what's up. Two pairs of eyes are better than one.

 

[COP RUNNER]

one option is to mail me your carbs and i can put them on my bike. If i get the same symptoms we know it's the carbs. Then i can break 'em down and see what's up. Two pairs of eyes are better than one.

man , thats what i would do ! No dought ! And pay him what ever he want's to fix them ! Whatever it is will be a tenth of what a dealer would charge & they would just screw them up !

 

[Shuriken]

One option is to mail me your carbs and I can put them on my bike. If I get the same symptoms we know it's the carbs. Then I can break 'em down and see what's up. Two pairs of eyes are better than one.

That's a hell of an offer. You've been more than helpful already. I don't think I can turn this down.

Let me yank the carbs and see what I find first. In the meantime, I'll send your adapter back. If I don't see anything amiss I'll send you the carbs and we'll go from there.

 

[Buster Hymen]

That's a hell of an offer. You've been more than helpful already. I don't think I can turn this down.

Let me yank the carbs and see what I find first. In the meantime, I'll send your adapter back. If I don't see anything amiss I'll send you the carbs and we'll go from there.

Mark is definitely one of the stand up guys on here that will go that extra yard to help someone out. :thumbs up::cheers: He just sent my laundry back, freshly washed, ironed and folded!... Thanks Mark! unk::biglaugh:

 

[maleko89]

Mark is definitely one of the stand up guys on here that will go that extra yard to help someone out. :thumbs up::cheers: He just sent my laundry back, freshly washed, ironed and folded!... Thanks Mark! unk::biglaugh:

Glad to help Buster. I hope you don't mind, I left you a present in one of your tube socks.

 

[COP RUNNER]

" LOL " :rofl_200::rofl_200::rofl_200:

 

[82ndCowboy]

Glad to help Buster. I hope you don't mind, I left you a present in one of your tube socks.

:rofl_200::rofl_200::rofl_200::rofl_200::rofl_200::rofl_200:

 

[Shuriken]

It's not a carb problem, as Mark ran my carbs on his bike and they were fine.

Does anyone have a spare VBoost sensor and/or ignition module I could try?

 

[Shuriken]

Question: Will the bike run with the boost sensor and vboost controller unit disconnected? I don't remember if I have tried that. Both devices connect to the wiring harness. Yes I'd loose boost but if the bike doesn't sputter, then I've found the problem.

If it still sputters with those devices disconnected, I will swap ig. coils. If it still sputters, I will swap pickups. Still sputters then I will have to assume wiring harness/connector problems and/or ign. module.

 

[maleko89]

The bike will run fine w/o vboost controller. The sensor feeds the ignitor which controls supplemental ignitino advance. I'm not sure how it will run w/o it.