XR 600R Cam timing...degreeing the cam?


I just built up my ancient but amiable '87 XR600 with the second top end of it's life. All new rings, valves, piston(100mm), etc. In the process, I chucked up the upper timing sprocket on a rotary table in the ol' Bridgeport and slotted the holes which locate it on the camshaft by 4 degrees in either direction(advance or retard). I had intentions of RETARDING the cam, realtive to the crank, to get a few more revs out of the ol' beast and shift the torque curve up a grand or so. In the process of assembly, I somehow got interrupted too many times and managed to advance the cam 4 degrees(from stock) instead. It runs great still, but the torque went the opposite way for my purposes. However:

I must say, for anyone needing a trail motor with killer bottom-mid(better than stock), this is DEFINITELY the ticket. It will now lug into a wheelie in what would've been way too tall of a gear before with a mere flick of the throttle, but flattens out real fast in the midrange. Like I say, not a desert motor but WOW on bottom.

Hopefully the same effect will be achieved, but in the right direction this time, when I retard it all the way.

I plan on retarding it back 8 total degrees from where it sits now, 4 before stock, soon. This was my original intention but turned out to be an interesting experiment anyway.

I will post again for those who are interested.

This was all performed with a stock cam, and nothing more than a fresh engine.

Tim Hillsamer

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