compression

[MIKE DAVIS]

what should the compression be for a newly bored CBX in psi. Not broken in.

[daves79x]

Depends on what compression the pistons are. Is it a Cruzinimage kit, or a higher compression Weisco, or something else. 170 at a minimum for any, higher for the high-compression kits.

Dave

[MIKE DAVIS]

It is a Cruzin Image set. set up at .001. valves were lapped. 85 psi accross the board

[daves79x]

185 you mean?

Dave

[MIKE DAVIS]

No, 85 psi.

[jnnngs]

Mike,

Did you do the reading with the throttle wide open (if the carbs are fitted)? It does make a difference.

85 is very low, may also want to check your gauge is reading correctly / accurate.

Paul.

[daves79x]

Even having not run the bike, I would have expected much higher. Do you plan on running it soon? Did you suspect something was wrong that led you to do the compression test on a new engine? If you are this far, and are absolutely sure the engine is assembled correctly (cam installed correctly especially), I'd run it some break-in miles and see what you have. But I still would expect much higher readings now. Do you trust your compression gauge?

Dave

[MIKE DAVIS]

I tried two different gauges, still the same. Even tried it withe the carb slides out. Also pulling only 2 1/2 inches of vacuum. I'm beginning to expect valve problems even tho I lapped them. 4,500 ft of elev. could be part of the vacuum issue but only a little. I think there's no choice but to pull the head, again.

[tevan]

I tried two different gauges, still the same. Even tried it withe the carb slides out. Also pulling only 2 1/2 inches of vacuum. I'm beginning to expect valve problems even tho I lapped them. 4,500 ft of elev. could be part of the vacuum issue but only a little. I think there's no choice but to pull the head, again.

Did you do a wet test on your head after laping them?