Sound like a heat, or electrical problem?

[Lucien Harpress]

I decided to take advantage of my day off and take a relatively long bike cruise. Of course, about 2/3 of the way through SOMETHING had to come up. Here's the deal:

Relatively short rides (30-45 minutes) are fine, no problem. But twice now when I've taken a trip of an hour or more, the engine starts acting up. It seems like I drop a couple cylinders, and at speed (55/60 mph) it starts backfiring like crazy. I've usually be able to pull the clutch in, let the motor drop to ilde RPMs for a minute, then rev back up and it's fine (apart from a "pop" or backfire).

I thought it might've been a heat issue, because it was easily 95 today, and the few times I let is sit for a bit to cool down, it seemed to run better for a while. In addition, short rides don't have the same problem.

I'm thinking it might have to do with the pickup coil wires. The symptoms seem identical, and I DID have to re-solder them already. I wouldn't think the heat would mess with them, though.... I'll pull the sidecover anyway to check it out, but I figured I'd get your opinion as well.

[TopCatGr58]

Hey Lucien,

I could be heat, but it could also be fuel starvation related...due to the gas tank cap vent not venting, and after running a while it builds a vacuum due to fuel flowing down/out, but no air or very little air getting in thru the cap!

Test is to leave cap open with less than a FULL tank, and ride it and see if it happens, or if you have a spare key, leave it in the cap, leave the cap tight, ride it till the problem occurs, then open the tank cap and see if the problem goes away!

Some folks have found their ballast resistor cracked, and separating under load/heat, but that usually will kill the bike since both coils aren't getting any power when it separates!

Yes, revisit the PU coil wires...you say you soldered them, but did you actually replace them with NEW flexible test lead wires??

T.C.

[petejw]

you could also try pulling the spark plugs
out and seeing what they look like, it should
give u an idea of whats going on inside the engine.

like tc stated recheck the pick up wires again, they can be a bugger at the best of times.

[motoman]

Soldering pick-up coil wire is NOT a good choice........second, kinda sounds like it happens heat associated.......pri. or sec. ign. source is likely culprit!.......occassional float hanging if same cyl./cyls. dropping from loading up with fuel, but anything associating with carbs is LAST thing to suspect.

[James England]

It sounds like fuel to me. My venty cap hole, as referred to by TC, was blocked only a few days ago. Almost completely (see thread about whistling cap which I started).

[DGXSER]

If it were me, I would definitely start with the gas cap vent. It is very likely from what you describe, and it is fairly simple to check and clean. If that is the problem and you start down the road of the pick-up coils you could chase your tail for days with no results. If it is not, you only spent an hour or two at most.