72 CB750 engine rebuild/resto-mod cafe racer...

[jojo]

Hello everyone, my name is Joe and ive been reading up on here for the last 3 months or so. Here is a quick intro with many many questions to follow.

I bought my bike for 1300 with a bad second gear but everything else was running. Rode it until i did something to the engine on the highway (went bang when i downshifted) and it stopped running well. It would still turn on but it seemed like it was misfiring.... so i decided to tear it down and dive in head first into my first build.

Pics coming soon.

 

[jojo]

Tearing down the frame. and my work bench on my kitchen table.

 

[jojo]

Couple of engine questions. When i was removing the valve springs with the spring compressor one of the springs broke from the base. Can i replace just this one spring or should i replace all of them? Also, intake valves 1 and 2 were stuck and gave me a really hard time when i was trying to remove them. Could the be bent? If so, how would i confirm/check that? One last question, is it normal for them the valves to look that (white residue)?

 

[SteveG]

Hi,
Replace them all, if one failed, the others may be on their way out. As for checking the stems, you can roll them on a flat surface like a sheet of glass and any bending will be obvious. It's also worth checking the diameter of the stems for wear while you have them out.

 

[jojo]

Thank you SteveG. I will spec them as soon as my mic comes in. Is it normal for the valves to look that way?

 

[jojo]

dropped the engine off at the machine shop to get a head job and hone the cylinders. turns out i had a tweaked intake valve and another with a bad seat which was causing it idle rough.