2000 VT750C: no power, then power

[flivver]

Originally Posted by rkforrest

Coils like to Open up when Warm so the problem wont be aparrent til they do

By open up, do you mean going open circuit (i.e. non functional)? I ask because the two most recent times it happened, the bike (and weather) were on the cool side. In fact, two times ago, the temps were in the low 30s and the bike had been ridden for less than a couple of miles.

Sent from my Kindle Fire using Motorcycle.com Free App

[John Hopkins]

I think rkforrest was suggesting that as the coils pass current they heat up..the only thing stopping them from shorting out is a coat of varnish around the copper wire, vibration and heat can cause problems as the wire expands..There is also a slight possibility of a dry joint, a poor connection between the connectors and the wires, although unlikely this will make the coil open circuit..

What is important is that both conditions can be caused by heat and leaving the swapped coils will soon show if the front pot stops firing instead of the rear..

As for could fuel/air cause the one pot to fire..yes..you have one carb for each pot..

John.

[flivver]

Update... I've gone out a couple of times since swapping the coils (and finding the bike to be running nicely). Went about 10 miles each time, always staying close to home, just in case. No issues.

I know little about coils and carbs (and clutches, oh my!), but it's looking to me like Mr. Hopkins may be on to something, with continuing to think it's a fuel/delivery issue. My intuition (which I don't trust, which is why I seek the counsel of the awesome people on this forum) says that if it were a coil issue, it would have recurred at some point in the last two outings. I'm leaning toward a disruption in fuel delivery due to some bit of detritus having dislodged.

(I know I've mentioned this before, but the tank was full of rust when I got the bike back in the spring. I don't doubt that there may be residual bits of rust that come loose as the bike warms, cools, hits bumps, whatever.)

I guess what still gives me pause is reliability. When the bike runs great, it runs great for a couple of months at a pop. With it having run poorly recently, I'm afraid to be more than a mile or two from home. I guess, eventually, I'll make my way further and further out.

[John Hopkins]

If you have a good fuel filter fitted the correct way round the rust in the tank should not reach the carbs..If you have a dirty fuel filter the residue has already reached the carbs and they will need stripping and at least cleaning..

You might as well get that done because it will either cure your fault or eliminate the fuel supply next time..

Don't just clean the carbs, fit new repair kits, they only cost about $30 for each carb.

John.