GS500 running on one cylinder. HELP!

[mattnes17]

Hey guys. Got my GS running for spring (after it running it since it was in an accident last fall) and decided to jet my carbs. The process went very well and my carbs were nice and clean and worked well (to my knowledge). So this week i was gunna take her out and i stared it up and realized that the right hand pipe of the header was HOT (burned my ring finger ) and the left one was almost cold. So i assumed it was running on one cylinder. I assumed spark: Good spark. Even swapped plugs. Still good spark. Swapped ignition coils: Still good spark but not firing on left cylinder. So i assumed no fuel: Plug was getting wet with gas tho... checked floats. Floats were good (not stuck) so i pulled the carbs and checked them over and they were fine... So my final thought in valves? Could either of the valves on the left cylinder be stuck? could the shims be bad? ANY info would be greatly appreciated.

[bombsquad83]

Did you check the fuel level in the bowl with a u-tube from the drain?  That the first thing I would do because I have very little trust in the needle valves on this bike.   The gas level might be too high or too low in the bowl.  If that is ok, the my next step would be a compression test.

[mattnes17]

Yeah, the fuel level in the bowls was fine. I will do a compression test asap and post the results.

[tb0lt]

In 99% of the "right pipe hot, left pipe not" cases on our 500s, the issue is a clogged pilot on the left carb... yes even if you just recently had them cleaned. This is especially true if you put the bike on the side stand more than the center stand.

There is a way to check it easily. Start the bike up cold. Put your hand on the left exhaust and rev the motor up to 4000+. If the issue is a clogged polit jet, the left pipe will start warming up since at this rpm, higher flow jets are passing sufficient fuel to run the cylinder.

[Kerry]

What model year is your bike?

If tb0lt's test comes back negative (the left pipe never warms up) and you have a pre-2004 model, there is a fairly simple electrical check that I can walk you through.  The object is to make sure that your "signal generator coils" (behind the right-side engine cover) are in good shape, along with all of the connectors/connections between them and your other ignition-related electronics.

I've posted relevant electrical diagrams and photos before, but that was years ago ... and never in a "standalone" form that was generally applicable.

[mattnes17]

In 99% of the "right pipe hot, left pipe not" cases on our 500s, the issue is a clogged pilot on the left carb... yes even if you just recently had them cleaned. This is especially true if you put the bike on the side stand more than the center stand.

There is a way to check it easily. Start the bike up cold. Put your hand on the left exhaust and rev the motor up to 4000+. If the issue is a clogged polit jet, the left pipe will start warming up since at this rpm, higher flow jets are passing sufficient fuel to run the cylinder.

I will try this tomorrow (this may work because i always ALWAYS put my bike on the side stand)

[mattnes17]

What model year is your bike?

If tb0lt's test comes back negative (the left pipe never warms up) and you have a pre-2004 model, there is a fairly simple electrical check that I can walk you through.  The object is to make sure that your "signal generator coils" (behind the right-side engine cover) are in good shape, along with all of the connectors/connections between them and your other ignition-related electronics.

I've posted relevant electrical diagrams and photos before, but that was years ago ... and never in a "standalone" form that was generally applicable.

My bike is a 97. If the previously mentioned test doesnt work i would greatly appreciate if you elaborated on this "electrical check"

[jestercinti]

Compression test?  That will tell if there is something wrong with the valves.

[mattnes17]

It was the carbs. I remembered i had a spare set of stock carbs, threw em on the bike, started up and ran on both cylinders. Looks like i need to clean my carbs for a 3rd time...