Intermittent loss of power

[CatatonicBug]

I have been chasing my tail on this one, so before I go and spend more money to replace parts that might not need replacing, I figured I'd ask the collective mind...

Bike starts fine, idles fine, and even runs the freeway fine - most of the time. It seems that lately, I'll be tearing down the freeway, and I suddenly feel like I'm running on 2 or 3 cylinders! I can maintain about 70-75mph on flat ground, but no more than that. It will drop out, then return, sometimes a few times per second. Usually, the problem lasts for several seconds to many minutes (i.e., the rest of my ride home). If I turn off the bike, and restart, the problem will go away for a few seconds, then return.

There is no correlation to speed, or RPM, as this has even happened in a parking lot. It does seem to wait until the engine is fully warmed up though. I have taken the TCI apart and re-sweated the contacts, I have cleaned all the terminals on it too. I did notice that my battery will need to be replaced soon, as I let it dry out this summer...

My only thoughts at this point are:
1. Might the dying battery cause this? I doubt it, since it is so intermittent, with the same AMOUNT of power lost all the time.
2. Am I missing a different loose connection somewhere?
3. Possibly a spark plug going bad? At $14/ea, I don't want to replace them AND the battery if I don't need to.

Any thoughts or insight would be appreciated.

[dbeardslee]

My brother recently had an issue that was very similar. It wound up being one of his pickup coil wires that was a little too free. It got up against the timing wheel which removed the insulation and exposed the core of the wire. Sometimes when the timing advanced it would get the bare part of the wire against the timing wheel and short it out, which resulted in it running on two cylinders. Then he'd hit a bump, or whatever, and the wire would move away from the timing wheel and it would start running on four again.

Just looking at it everything seemed okay. I had to feel around on the wires to find the bare spot. After that I redid the clamp that holds the wires in place and covered over the bare spot with some self fusing tape. Problem solved.

[CatatonicBug]

Unfortunately, I checked that too... I even found a wire that had some cracked insulation, and spliced in a new wire. The problem didn't change at all.

[dbeardslee]

Maybe you've got a coil going out. Sometimes they'll check out fine when they're cold, but fail when warm.

[CatatonicBug]

Do they go out like that? I thought they just died all at once. I'll double check the connections on them at least.

[dbeardslee]

Do they go out like that? I thought they just died all at once. I'll double check the connections on them at least.

I added this to my last post, but we were probably posting/editing at the same time. Sometimes they'll be okay when cold but fail when warm. I'd get a read on the plugs when it's exhibiting the problem and see what your pairings look like.

[bikerphil]

I had a similar problem not too long ago, bike would drop 2 cylinders at random. It turned out that the 4 wire connector at the TCI had poor connection due to stretched out terminals. I put a new 4 pin connector on and it was fine after that. This connector goes to the PU coil harness, there is also another connector in the harness behind the fuse panel, I just cleaned/crimped that one. The terminals can be removed from the connector with a tool and then crimped closed and reinstalled.

[BA80]

Try a different TCI Marshal, you may have a solder connection that's cracked making intermittent contact.

[CatatonicBug]

I was contemplating replacing the terminals on the wires in the connectors at the TCI. Had not thought of looking behind the fuse panel. The terminals look ok, but replacing them won't be too difficult, and I already have the new terminals. That will probably be my project tonight.

[CatatonicBug]

Try a different TCI Marshal, you may have a solder connection that's cracked making intermittent contact.

I don't have access to one... I have re-sweated the solder connections in the TCI though. No change to the problem with I did that.

[BA80]

Does it go away if you let off the throttle?

[CatatonicBug]

Nope. Same issue if I let off the throttle. The only time it seems to go away is when I turn it all the way off, and re-start the engine. But then, it just starts again shortly thereafter. I have even had it die at a light because it happened at idle.

[BA80]

OK. That sounds electrical. Whatever it is it probably doesn't show up until the bike is warmed up. Correct?

Have you ohmed the pickup coils?

[BA80]

I have even had it die at a light because it happened at idle.

Mine did that when I had a plug going bad.

[CatatonicBug]

Yes, it seems to start fine when cold, and the problem doesn't start up until the engine warms up. I have not ohmed anything.