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Need help with bad compression on scooter?
I have a 1985 yamaha riva jog that had sat in a garage for 11 years. I recently put new rings in it because the old ones were corroded and allowed blow by. The cylinder has no scratches at all. After installing the new rings I still only have about 50 psi! When I put a little oil in through the spark plug hole and did another compression test I got about 150 psi. Are the rings bad? What else should I check???
3 Answers
- Jon PLv 59 years ago
A cylinder should be honed before replacing rings. A bore can have no scratches in it and still be worn. Pistons wear too. A cylinder bore gauge can check the diameter. Also with the compression ring only, placed squarely in the cylinder with the piston skirt, the end gap can be checked with a feeler gauge. The biggest wear area is usually just above the exhaust port. These specs will be in a manual. Considering it's age I would get it bored to the next oversize and have new piston, rings, and bore.
Source(s): Technical training and experience. - Candid ChrisLv 79 years ago
The new rings need time to seat properly and you adding oil to the cylinder was sort of a mask to tell you that things will work.
Don't change anything, just ride the scoot without going to any extreme RPMs for the first few hours and don't bog it either. UP and DOWN in the revs. Pain in the @ss but it needs to be done.
Source(s): Riding/racing/wrenching for 48+
