Topic: Freshly rebuilt CB400F engine, bad compression in one cylinder

[monstergarage]

I just got a compression tester this week (don't know why it took me so damn long to get one) and thought I'd try it out on my freshly rebuilt engine, 3 cylinders were perfectly fine, I think, got to about 105-110psi using the kick start before I got worn out, would probably go further with a starter, but that last one was only getting up to 60psi. Full disclosure, I haven't started this engine yet after rebuilding, the piston and rings were so clean I could eat off of them when I was finished, so they have no carbon or oil in the rings yet. A little bit of oil in the spark plug hole and it was getting better compression than the rest of the cylinders.

So the big question, should I tear it down now, or wait for the engine to start up for the first time and break in a little? I'd imagine with a little bit of carbon and oil between the rings it would probably be fine.

So what do you think?

[strynboen]

is the valvets adjusted..if they are to teight there is no kompresion ...

broken rings is often a problem if the differens is so big..and one is fallen så far aut from the rest...dirt can not..is the rings gaps moved so they not are in a line..so blow davn kan run througt the gaps in a line..if that is the problem..just run the engine and they vil turn..and solvent the problem by themself

[MoMo]

If you broke a ring during assembly you'd most likely notice it while turning the motor over...Larry