Gremlin

[scootstado]

Well, my "gremlin" has come home to roost. It had always been heat related, meaning it did not happen until the bike had been running awhile and happened faster the warmer is was out. The original problem felt like running out of gas then a simple roll off the throttle a pull in of the clutch would clear it for another 5 to 10 miles and the problem would happen only at mid speed, not idle or highway speeds. Yesterday after a 20 min ride the bike just died and I pulled to the side of the road and it would not idle or move when you gave it gas just backfire and die. Tried for 10 min., no luck would not stay running or move without dying. Got some help and put in my truck and brought home. After it cooled off it started OK and ran fine. Today I swapped out the coils and started it up and it ran fine for 15 min then cough, spit and fart and die. Seems to be running very hot for some reason. All pipes are hot 1&4 hotter than 2&3 but none cool. Won't take any throttle without dying but start and run again when it's cool. Is there anything else electrical I could swap out that might be dying with heat. I've done the pickup coil fix and as I said swapped out the coils. I checked all the breather hoses and gas tank vent all seem OK. Any suggestions for this problem? This is driving me nuts (as though I had far to go) Help! I need to get riding again.

[MartyA]

HI Russ!
Might be running lean? When it suddenly cuts out at speed, check the plugs. That is similar to a throttle chop.

Carb boots snug against the motor? Something moving after heating up causing more air to get in?

Also sorta sounds almost like vapor lock.

Vacuum advance sticking? Or the centrifugal advance?

If you test and get spark at the plug after it gets hot and suddenly stops, it might not be electrical.

[Geezer]

My 11 Special was doing that and it turned out to be a fuel flow problem. The next time it happens, one a time drain the carbs into a tin can and see if they all have about the same ammount of gas.

On my special it was easy, I just flipped the lever to prime and it ran great. Your milage may very.

Geezer

[dragxs11]

I'd have to disagree with MartyA on this one. I think it's rich. Your pipes will get hella hot under rich conditions due to afterburn. I'm having some serious richness problems due to pilot jets being to big right now and mine heats up bad! This also explains why it will run when cooler... in effect, your choking it, without choking it. Sounds like the main jets are too big. They operate after 1/4 throttle. As your bike warms up, it will begin to load with too heavy of a mixture, until it won't take it anymore. Incidently, the spitting and poping occurs with mine as well, but at idle instead of after the diaphrams lift. From what I've experienced, and all I've read, ignition problems are few and far between. Hope this can help a bit. I can only speculate cause I can't be there with the bike as it happens.

[MartyA]

Yeah, could be. I was thinking lean because if it was running rich after 20 minutes of running the plugs would foul to where it would not start again when cold without changing the plugs. Still would like to know what they look like after it quits.

Russ said it backfires. Does it matter which direction the backfire? Through the carbs or through the pipes? Would that be a clue?

[dragxs11]

I'm not the greatest expert yet on mixture settings, but I'm learning a lot fast... Pulling the plugs as soon as it messes up would be the way to tell whats going on. Some plugs can be pretty resiliant when it comes to mixtures, I've found. I'm using NGK's right now, and though I have been fouling them eventually, they hold up better than the cumbustion chamber under the crap I've been feeding mine. I wouldn't be too surprised if the engine is giving out before the plugs do. But like I said, these are only Idea's. I don't know the history of your bike to make a more accurate analysis.

[TopCatGr58]

Hey Russ,

Well, I'm going to play devil's advocate, and agree with Marty, that it sounds like fuel starvation to me, too. You say you've checked your vent hoses. How are you fuel lines run, is there a big dip in their length below the level of the carbs? Having it die when trying to give it throttle points to very lean, cause when you open the throttle you're letting more air in, and if there's not enough gas to mix, poof, cough, backfire, die!! Next time it dies, try popping open the gas tank cap, see if you hear a big rush of air, if so, then you may have a vacuum lock, gas not able to flow from the tank after so much flows, too much vacuum building up inside tank, outside air pressure equal or greater than inside tank pressure, won't allow it out thru petcocks! These bikes and what most GURU's have said is that engines run or get leaner as they warm up, the fuel vaporizes more, etc.! Also, before venting the gas tank, pull a fuel hose off of a petcock and see if fuel will flow from it, if not, again=fuel flow problem, not electrical!?

Also, is your oil light working? Poor oil flow can cause it too overheat as well, and that can keep it from running, even seize it up? My bet is on the fuel system, not getting enough. YMMV

T.C. also not a GURU, just interested Xser!