I hate this bike (one cylinder looses spark)

[darcy77]

First time poster (long time lurker) with a problem that has me stumped. I'm not a mechanic, so please be gentle with your responses.

I bought a 2001 GS500 last fall as a winter project. According to the seller, the bike ran poorly and the Suzuki dealer told him the pistons needed to be changed. I got the bike home, and it ran great when cold, but after 5-15km the right cylinder stops firing. It still does this, despite me having either replaced or checked the following:
*Head, Cylinders, Pistons, and rings replaced
*Carbs rebuilt
*Coils replaced
*CDI replaced
*Spark Plugs replaced
*Oil and filter changed
*Pick up coils tested and in spec.
*Battery is great
*Compression is good.
*Valve clearance checked and adjusted

On the upside, I now have a great collection of spare parts, and can strip this bike down in no time flat. But this bike still drops the right cylinder after about 10km. It doesn't miss fire, it just runs awesome, then in an instant the right cylinder drops.

Anything electrical I can stick the multi-meter to and test is in spec, but after all this I'm of the opinion that it is some sort of electrical problem.

Anyone have any thoughts; I am at my wits end, so any helpful advice would be appreciated.

CONCLUSION: And the winner is Paulcet.

I took the bike for a ride up the parkway (even got pulled over for speeding by a cop who was nice enough to let me off with a warning), and when the right cylinder stopped firing, I jumped off, checked the resistance, and one of the signal generator coils was broken (open circuit).

Thanks so much for everyone's help, you've saved this GS from being pushed off a cliff.

[Big Rich]

Hmmmm. Only the right side, huh? I know you said the coils are good, but have you tried swapping the left and right coils? That would eliminate that completely. Could possibly be the timing but a single wire heating up after 10k isn't likely.

Speaking of which- is it only after riding for a while or does it do it idling for a while as well? Only other thing I can think of is a blocked vacuum passage in the right carb, but that doesn't make much sense either.

[RichDesmond]

Try a new spark plug cap on the bad side. Very common in the SV world, the caps loosen up over time and don't make a good connection.
No guarantees, but at least it's a cheap/easy experiment.

[Paulcet]

Someone here had a bad pickup coil that would only fail when hot.

[darcy77]

And the winner is Paulcet.

I took the bike for a ride up the parkway (even got pulled over for speeding by a cop who was nice enough to let me off with a warning), and when the right cylinder stopped firing, I jumped off, checked the resistance, and one of the signal generator coils was broken (open circuit).

Thanks so much for everyone's help, you've saved this GS from being pushed off a cliff.

[utgunslinger13]

Thanks so much for everyone's help, you've saved this GS from being pushed off a cliff.

Glad you were able to figure this out!  I know what its like to chase electronic gremlins and know how aggravating they can be!

[The Buddha]

And the winner is Paulcet.

I took the bike for a ride up the parkway (even got pulled over for speeding by a cop who was nice enough to let me off with a warning), and when the right cylinder stopped firing, I jumped off, checked the resistance, and one of the signal generator coils was broken (open circuit).

Thanks so much for everyone's help, you've saved this GS from being pushed off a cliff.

You need to post and ask questions and do proper trouble shooting and searching here before replacing parts @ random.
BTW The dead when hot coil probably was me, cos it happened to my 89 in 1998 and sledge and maybe someone else posted about it opening up when it got hot. Of course its happened since to me on other makes, yamaha's in particular.
Cool.
Buddha.

[Paulcet]

Happy to help darcy77!  Now, tell me how you find a bike with an apparent terminal illness for cheap, and it really just needs a cleaning and less than $100 in parts?

You need to post and ask questions and do proper trouble shooting and searching here before replacing parts @ random.
BTW The dead when hot coil probably was me, cos it happened to my 89 in 1998 and sledge and maybe someone else posted about it opening up when it got hot. Of course its happened since to me on other makes, yamaha's in particular.
Cool.
Buddha.

Yeah, might have been the Buddha, but I was thinking it was someone else...  In all fairness to the OP, if he had posted the question, he probably would have gotten as many answers as parts he has replaced!    Well, one more, being the right one.