Motorcycle Repair: motorcyle engine trouble, suzuki gs1100e, pod filters

Question
I purchased a 1981 Suzuki GS1100E from a private owner. It has a Kerker pipe, pod filters and has been rejetted. It runs well wide open, but at 1/2 throttle it will tend to carbon up then start to break up. It also doesn't hold a good idle. I have done a compression test and it is on the low side. I'm want to know if it is a jetting problem or elctrical, mechanical issue?

Answer
Hi David,

From the description of the problem, I can safely say the carburetor's mid-range needs tuned. Most likely cause is too large main jet size supplying fuel to the needle jet & jet needle.

You didn't include cylinder compression readings so I can't give an opinion on that. An engine needs adequate compression for the carbs to function properly.

Also perform a cylinder leak-down test to determine the  cause of compression loss.

Respectfully,
mark Shively