CAM you help me....

[Lester]

Hey guys,

I just picked up a 1980 XS650 for the wife.... its been sitting in a barn since 1994 with a rebuilt engine that wouldn't start after rebuild.

Any how it turns over OK and all else seems good so I got to thinking.... the cam.... I pulled off the exhaust valve covers and turned the engine.... sure enough.... the valves didn't move simultaniously.... so the "performance" cam that was fitted during rebuilt is for a refased engine.
I'll leave the refaseing to the experts... I need a standerd 650 cam.
Snooping around E-bay I noticed some cams are 36 tooth and some 34....
My leg is in a cast at the moment so I am unable to pull the cam out right now, but I would like to order one so I can get cracking as soon as the cast goes off. Which cam do I need 34 tooth or 36 thooth? Any thing I can look for with out pulling the cam out.

Thanks

Lester

 

[XSLeo]

The exhaust valves don't move together. When one cylinder is comming up on compression the other is coming up on exhaust. One cylinder the valve is closed, the other it's open.
Also if the cam where rephased the crank would have to be too. You can't run a stock cam on a rephase crank. Or a rephase cam with a stock crank.
I think what you need to do is pull the plugs and turn the engine over with a finger in the plug hole and watch your timing marks.
The left side is easier to watch, as you turn the engine and it comes up on compression you will feel the air push on your finger, this tells you both valves are closed. You will see this by watching both valves move. When the timing marks line up at TDC both valves should be loose.
Now put your finger in the right side, watch the valves as you turn the engine. When both are closed and coming up on compression look in the plug hole to watch the piston as it comes up to TDC. Once you find TDC this way look at your timing marks. If they are pretty close then your not rephased. If they are about 90 degrees away then you have a rephase.
Your 80 engine uses the 36 tooth cam sprocket, the 34 was the early 256 engines, Yours is either a 447 or 533 engine.
Leo

 

[Lester]

The exhaust valves don't move together. When one cylinder is comming up on compression the other is coming up on exhaust. One cylinder the valve is closed, the other it's open.
Also if the cam where rephased the crank would have to be too. You can't run a stock cam on a rephase crank. Or a rephase cam with a stock crank.
I think what you need to do is pull the plugs and turn the engine over with a finger in the plug hole and watch your timing marks.
The left side is easier to watch, as you turn the engine and it comes up on compression you will feel the air push on your finger, this tells you both valves are closed. You will see this by watching both valves move. When the timing marks line up at TDC both valves should be loose.
Now put your finger in the right side, watch the valves as you turn the engine. When both are closed and coming up on compression look in the plug hole to watch the piston as it comes up to TDC. Once you find TDC this way look at your timing marks. If they are pretty close then your not rephased. If they are about 90 degrees away then you have a rephase.
Your 80 engine uses the 36 tooth cam sprocket, the 34 was the early 256 engines, Yours is either a 447 or 533 engine.
Leo

....... got ahead of myself didn't I.
Of'couse I realized this just as I presses the "submit post" button.....

Thanks fot putting me straight Leo
I'll limp out there tomorrow and do the check you mentioned.

cheers
Lester