1980 CB750C Restoration

[Kajpaj]

Hey Forum!

Much to my fiancé’s laughs in disbelief, I bought a complete project bike, the bike it self has not ran for about 20 years. As you can see the bike does not only need some tlc but also parts...

I am a complete novice when it comes to bikes and gas engines so you cannot dumb things down too much for me. I have some experience with Diesel engines so I know how to use a wrench.

So far down the road,

I have done all the valve adjustments and getting fairly consistent compression (80psi) on all cylinders. Done some electrical work as well and have sparks in all cylinders as well.

The challenge that I am facing right now is that when I turn the engine with the starter it turns “unevenly” and slow, battery is fully charged and drops to 9-10V under load, I’ve tried a different starter with new brushes and I have bypassed the solenoid.

Still having issues...

https://youtu.be/E5BBq49cMM8

Any suggestions?

 

[irk miller]

80 is not good compression. It won't run under 90. Are you completely opening the throttle when you test compression?

 

[Nybz]

Sounds like low battery or dirty connections.
What’s the history on the battery? They don’t like to sit discharged too long.
Check the main fuse, when I first touched mine it crumbled into dust. Those old dog bone fuse can be upgraded
Check all connections, and be mindful of grounds!

80psi is non running state for these bikes. Which come stock at 170psi
There are ways in which you can find where the compression is escaping from.

There are online forums for these bikes cb750c and cb1100f.net that are super helpful


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