78 gs750 valves snapping on the cam

[Guest]

[FONT=Arial] So Ive been tinkering with this basketcase of a bike for a while. I put it together and the Valves would snap violently closed on the cam when turned over. I found that one cam was 180* out of time and I assumed the valves were bent. So I bought a head off of a "running bike" on eBay because it was cheaper than valves. Now it's doing the same thing. Did I buy a piece of junk or am I missing something?

[Agemax]

the valves shut pretty sharpish because they have too! there are some pretty strong springs acting on those valves to keep them shut whenever they are "off cam"

[avgjoe86]

The problem is that the valves hang open after the cam has flattened out. So much so that It won't build compression. Then the buckets smack into the cam.

[Nessism]

I suggest that you remove the valves and check them for straightness per the service manual. Clean the head and buckets and make sure they don't bind in the bore. Assuming all the parts check out, reassemble with new valve stem seals after lapping the valves. Good luck.