Hi all,
Been a long time lurker and just recently joined the scene. Great forum and knowledgeable people around here! I've recently picked up a 77 CB750 K which will slowly be converted to a "cafe monster" (if there's such a name for it yet) in the coming fall/winter seasons. I have some design ideas but they haven't been drawn out or photoshopped...yet.
In the meantime, I am working on the getting the bike running properly and to give me an idea of what she needs overall. First off some information. Currently,the bike is very responsive throughout the throttle band but backfires on deceleration or when shifting regardless of RPM. Upon initial timing inspection, I discovered the timing was maxxed out - advanced which explains the backfiring. Curious, I put the timing back to spec and she idled smoothly and throttle response under no load was hella nice. However, under load, acceleration was quick and then bogged to the point it stalled. Well, I assume it was the PO's quick fix to a big problem...
Further inspection of the carb revealed fuel seaping to the point of spraying out from between the lower bowl and upper carb assembly (nearest the pump) when the throttle is actuated. As such I have completely broken down the carb and concluded it requires a new gasket among other things. It seems the PO has had the carb serviced before indicated by worn screws.
I'm currently waiting for my gaskets kits and carb rebuilt kits to arrive in the mail. Now i realized after dismantling the #2 carb which houses the accelerator pump that there was no gasket or o-ring sandwiched between the accelarator pump opening and the carb casing? IS THERE SUPPOSE TO BE AN O-RING or some gasket there? If so, it explains the lack of fuel getting into the carb because it's leaking outside the carb. If anyone can confirm this please let me know. Much appreciated.
Other problems discovered:
- #1 needle heavily worn and pitted
- pressure springs on #2 to #4 slide valve assemblies were not seated properly on the needles (they were off center and bent - does this affect fuel delivery?
Hopefully, replacing and properly assembling the carb with new parts will let me run her around for the rest of the summer. Otherwise, the rest of the bike is mechanically sound.
