RE: GS550 still running bad.

[Anonymous]

Ron, I have indeed already tried swapping plugs, and replacing them too, cyl 2 still dead. Good ideas with the propane fired engines though. This thing is beginning to really become a pain. I have just for fun, tried swapping plug wires back and forth, and have tried 3 different carbs on cyl 2. still no go. the only other thing I can figure is maybe for some reason I have weak spark and cyl 3 can fire easier than cyl 2. possibly? hate to get a new coil though without knowing. can't swap cause they have different connectors. any other ideas???

thanks
Matt

[Anonymous]

How is your compression in that cylinder?

[Anonymous]

compression is great- 150 psi, and leakdown is 3%

[earlfor]

Re: RE: GS550 still running bad.

Hmmm, cylinders 2 and 3 fire off the same coil, so if 3 is fine and 2
doesnt fire and you have swapped the leads between 2 and 3 and it makes no difference, then I doubt the problem is coil, leads, or plug caps. Swapped plugs, so not that either. Three different carbs and none of them make cyl 2 work either, so doubtful it is the carbs. Compression is good, so also not that. You say cylinder 2 is dead. Do you mean its exhaust pipe stays completely cold regardless of how long you run the bike or what rpm range you run it in, or does it warm somewhat? If we assume that everything is working properly, cylinder 2 can still only fire/produce
power if there is sufficient vacum through the carb to draw a fuel/air mixture. I would put a vacum guage/manometer on the cylinders and check to see what the vacum draw is on no.2 compared to the other cylinders. On my 750, there are "O" ring
seals on the carb intake boots between the boot and cylinder head. With age, these dry out and leak, causing loss of intake vacum. If these seals are bad and there are intake vacum leaks on all four cylinders, the engine will not run at all even though everything else is perfect. I would not switch intake boots to check if it makes a difference since the "O" rings get brittle and you would likely not get them to reseal once disturbing them. They are still available from the dealer and I bought four intake "O" rings for my bike......cost was about five bucks for a set of four.

Earl

Ron, I have indeed already tried swapping plugs, and replacing them too, cyl 2 still dead. Good ideas with the propane fired engines though. This thing is beginning to really become a pain. I have just for fun, tried swapping plug wires back and forth, and have tried 3 different carbs on cyl 2. still no go. the only other thing I can figure is maybe for some reason I have weak spark and cyl 3 can fire easi
er than cyl 2. possibly? hate to get a new coil though without knowing. can't swap cause they have different connectors. any other ideas???

thanks
Matt

[Anonymous]

by dead I mean that it stays mostly cool at idle, heats up as I rev it, and seems to sputter at high Rpm.

Matt

[earlfor]

Matt

If when you start the bike, you start it with choke only, hold the choke to warm it up and never touch the throttle. If the choke circuit on #2 is working, the pipe HAS to heat up. If once the bike is warmed up enough to idle at say 1000 rpm and STILL never having touched the throttle and after running a while, the pipe is cool or cooling down, then the pilot is not flowing fuel. As you rev it up if the pipe warms, then the midrange is working. If it sputters at high throttle settings, we need to know if it is blubbering, saying Buuuuu, or going flat. You may still have some clogged spraybar holes, or the needle could be in the wrong position. Is it only cylinder #2 that is missing at high rpm or is it all of them?
The first thing I would do is to put a vacum guage on cylinder 2
to make sure there is vacum there, because if there isnt, you could spend the rest of your life cleaning jets and it will do you no good at all. If you dont have a vacum guage, any bike shop can hook one up to the fitting on #2 carb on the intake boot between the carb and cylinder head and tell you is there is good draw. It should only take a few minutes for them to do this and cost should be minimal as there is only one screw to turn out and a fitting to turn in.

Earl

by dead I mean that it stays mostly cool at idle, heats up as I rev it, and seems to sputter at high Rpm.

Matt

[Bill + Karen]

This sounds like a vacuum leak to me try the spraying of the carb cleaner trick. Safe Riding, Bill