ST90 Loses Compression when hot.
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Join Date: Dec 2001
Location: Gahanna,
OH
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ST90 Loses Compression when hot.
I think the answer is apparent but just wanted to confirm. I have an 8 year old Supertigre 90 that has been stored for 7 years. It has about 30 flights on it. It starts fine cold and runs strong but once warm when you go to idle it slowly stalls and wont restart. The compression seems to go away. Doesn't have nearly as much as when cold. Doesn't even bump when turned over by hand when hot. When it cools down completely it starts back up easily and repeats the cycle. Piston ring? Some lite score maeks on the piston and liner but not too bad.
Rex Birkinbine
Rex Birkinbine
#2
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RE: ST90 Loses Compression when hot.
It sounds like the ring has lost its ability to push out against the liner and cause a seal. When the engine gets warm, the liner expands away from the ring and you lose compression. You can try a new ring. Lightly sand the inside of the liner with 400-600 grit wet or dry paper coated with oil. We just put a piece around our finger and lightly smooth the inside. You'll only need a few strokes.
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RE: ST90 Loses Compression when hot.
Thanks Bill. Appreciate the help. Love those Supertigres. They have to be the best value out there. I have several that are 10-15-years old and find it amazing how long they last and how well they perform.
Rex Birkinbine
Rex Birkinbine