Topic: Compression Test?

[Bee Joenz]

Hey guys -

Just a quick question: I have a friend doing a compression test on my 77 cb750 F and he's getting a reading from left side 1 = 90 pounds and 2, 3, 4 = 60 pounds. I know that they're all supposed to be at 170. Curious as to whether this will require a rebuild/replacement of the engine or what exactly.

Any and all suggestions would be greatly appreciated.

The engine is being tested with the carbs on but again my concern is the fact that the pounds are so low in the first place.

Thanks

[Johnie]

Are you doing the test with the carbs wide open? Would help to let us know a bit more about the motor like how long it was sitting. How many miles? Many times the rings are just a bit stuck and once you do the 3,000 mile tune up and ride the bike they will free up and compression will rise.

[70CB750]

Dont sweat the 170 either, it depends on the tester a lot.

Important is to have values within 10% and daily ridden bike will have better values than a fresh barn find.