XR350 camshaft, extra lobe normal?

[y5mgisi]

Well its not an extra lobe actually. Its more of a hilical looking area like a spedo gear would be ran off of it. A buddy of mine has this bike and were trying to get it running. We puller the valve cover to varify cam timing and noticed it. It looks like someone ground all of the "teath" off of that odd little lobe. anyone know about this?

 

[Ol'89r]

Well its not an extra lobe actually. Its more of a hilical looking area like a spedo gear would be ran off of it. A buddy of mine has this bike and were trying to get it running. We puller the valve cover to varify cam timing and noticed it. It looks like someone ground all of the "teath" off of that odd little lobe. anyone know about this?

Could be off an XL350, tach drive.

 

[y5mgisi]

Really? They didnt run the tack off the coil or somthing? But this cam should work fine though? Also do you know why we have two timing parts on the flywheel? and which one im supposed to use to time it?

 

[dirt bike dave]

FWIW, there is apparently a Post #4 that is invisible. I can't view it at all. I think that has happened with other users before.

I'm not familiar with that engine's internals, but maybe it has something to do with an automatic compression release that lifts a valve slightly to aid starting.

 

[anthonysimo]

I have rebuilt few of these and it does sound like you have a cam from a XL350. These did have a drive in the middle of the cam.
XL350 had slightly smaller gudgeon pin, smaller carb(s) and wider ratios in the box if I remember correctly, the cams may have slightly different profiles.