tuning question

[myfastbike]

I've just installed a new engine in my bike and am having trouble getting it to run correctly. Just before she blew last year I had the carbs cleaned, sync'd and bike running perfect. Now, It idles fine but I cant rev past 4500rpm. The motor, carbs, and exhaust are all stock. The pilots are 1-3/4 turn out (where I had them set previously) and the carbs are sync'd albeit the vacuum is much lower than my old bike 0-12 vs 18+. I've checked the compression and its consistant at 135psi. What gives? Any help would be appreciated!

[Hammerhead]

You said the vacuum was low. This would indicate a problem somewhere in the vacuum lines or system. Check the vac lines and connections and anything connected to them. Also check the diaphragms in the carbs for leaks and proper operation. If nothing is found there, check intake valve clearances and intake cam timing.

[myfastbike]

Supposedly this engine was just serviced and the valves adjusted prior to its removal. Based on the compression I've ruled out the valve clearance but I have not checked the timing yet. I'm with you on the vacuum issue but there really isn't much to that side of the system when the air box it. I've checked the diaphrams before I posted and they look great and are operating fine. I thought maybe it had an ignition advace installed (which could explain a drop in vacuum) but it's stock. Once I get a new gasket on the timing cover(tonight) I can run it again to make a few more checks. I Also just noted a typo on the vacuum #'s in the previous post. It's 10-12 not 0-12.

[Hammerhead]

If you don't have the air valve block-off kit or the homebrew version, check all those connections and the valve itself which is operated off the vacuum system. something could have gotten knocked loose in the changeover.