Perplexing Problem - Part II

[Shuriken]

You're welcome. Manual says to test compression when engine is warm. I would re-test...maybe you're not as close to that 14 PSI differential.

One option is to take it to the dyno. They use an ignition pickup which can help in detecting ignition problems. This helped me years ago detect failing Dyna hot coils.

I'll retest warm before I send your adapter back.

I do have a timing light. I suppose there might be some way to use it while riding the bike to see if the light cuts out. Don't know how I will get 12v to the light, plus clamp on to a lead, then drive the bike.....

 

[shawn kloker]

Hi guys,

This is part II of Perplexing Problem (http://www.vmaxforum.net/showthread.php?t=4572).

I'm still trying to figure out why I'm getting some kind of sputtering - some days better, some days worse.....

Took a ride today and the bike wanted to sputter and cough regardless of RPM. This makes me think the problem is not a fuel/carb issue. I have gone through the carbs 2 or 3 times very carefully. I don't have any vacuum leaks that I know of, either, as I've replaced all of the rubber parts.

Anyway, I was just messing around trying various things. Took the DP8REA NGK plugs out and gapped them at 0.033. Checked coil wires and caps, etc. Then I started the bike and ran it up and down the road to fully warm it up. Still had flubs and sputtering.

Brought the bike back, started messing with idle mix screws one at a time. In until the bike wanted to die, out until idle stopped increasing, then back in somewhere in the middle. Did this on all 4. Took the bike out. Still flubbs and sputters but less backfire out the drilled exhaust and more "fuel" smell out the exhaust.

Pulled back into the garage thinking it just has to be some kind of spark issue that has developed since I got the bike. Lifted the plug caps off each plug one at a time to listen to how differently the engine would run when a particular cylinder didn't fire. I discovered that #2, #3, and #4 all seem to drop the engine speed about the same. But #1 hardly drops the engine at all.

In other words, when #2, #3, or #4 are disconnected, the engine really starts laboring just to keep idling. But disconnecting #1 doesn't change it as much.

Started fiddling with the idle screw for that carb and between full in and full out, that cyl pops infrequently and in a mushy sort of fashion. Doesn't seem like the idle mix screw has much effect on that cyl as far as producing a proper combustion on the proper cycle.

Poor compression? Or a problem with that carb's idle circuit? Or, problem with the ignition coil for that cyl?

If #1 isn't pulling it's weight, would that create v-boost issues? I can't tell if this happens at all RPMs on this cyl but it sure isn't working like the others at idle. It might occasionally be firing when I'm out on a ride, which may explain the popping and lurching when I'm trying to cruise. I know it doesn't take much throttle to hold cruising speed in town, so this may be reasonable....

#1 and #3 coils and caps are stock but #1 and #3 coil wires are some non-OEM yellow wires that say "radio supression" on them....

So..... there are a few things I can do, if I have some help.

1. I can do a compression check on that cyl, if someone has the right adapter. I've yet to find one.

2. I can try another set of coils/wires/caps if someone can lend me something to try.

Open to other ideas. Anyone find any clues that stand out in the stuff I've posted?

This sounds to me like The cruising problem is needing to do the shotgun.

 

[Shuriken]

All cylinders are over 150 when the bike is warm:

9-1-08, elevation 5700, temp 70f, engine warm

#2: 151 #4: 155
#1: 152 #3: 155

I'm assuming the engine to be in good shape for its age and mileage and will continue to focus on carbs and electrics.

Very frustrating problem. Took it out tonight and had no sputtering whatsoever.

 

[Shuriken]

Took the bike out again today. Sputtering, crapping out on the mid-full throttle....

So I had my friend get on it and I rode behind him on his BMW. He gunned the max and I saw a huge plume of sooty black smoke puff out the right hand pipe. He said it was sputtering all the way up the RPM range.

So this is a clue to what is wrong. Anyone have any ideas now?

 

[maleko89]

You have stock exhaust correct? Right side muffler is fed by #1 and #4 cylinders. When this happens does one cylinder feel cooler that the other? Sticking valve? Broken valve spring? Valve lash?

 

[Shuriken]

You have stock exhaust correct? Right side muffler is fed by #1 and #4 cylinders. When this happens does one cylinder feel cooler that the other? Sticking valve? Broken valve spring? Valve lash?

Stock exhaust with the end plates removed and holes drilled in the ends. I want to weld the holes up and start from stock.

I don't know about the temperature of the cyls.

I think it has to be dumping way too much fuel into the engine or the ignition cuts out for some cycles.