Spree starts, idles, runs well to about 20 mph at which point it won't accept any more throttle without running roughly. Good steady response up to this point. Head and top of piston have been thoroughly decarbonized. Spark plug is clean and tan. Why is my compression so high? Exhaust system clogged? If so, how can I test and confirm this? Or, what else might cause my high compression reading?
1) Are you running a stock head gasket? Should be .020 "
2) Do you have a head gasket?
3) If you have a slide micrometer, measure the distance from the surface of the head gasket face of the head to the top of the head casting. Should be about .020" also.
Smaller numbers on any of these raise compression. Increased compression is not a problem unless carbon is present. Your running problem is elsewhere.
Exhaust clog might cause this, but unlikely. If the head was heavily carboned you should clean the exhaust and exhaust port.
Yes, I located my head gasket and it is installed. I assume it to be a stock head gasket. It appears to be aluminum. Is that correct? Don't know the thickness yet. The carbon on the head and piston didn't look too bad to me (1/16" at the thickest spots, mostly less). Gotta go. Thanks
Replaced compression tester guage with spare. Ran a new test on the compression with the same old results - 140 lbs. As suggested, I will check and clean exhaust port when I can. Stay tuned.
I cleaned the exhaust port as best I could with the cylinder in place. Quite a bit of tan dry crud in there - kinda like having the dental hygienest clean your teeth. Compression is now down to 128 lbs. Test ride tomorrow.
