xr70 valve adjustment

[bill02364]

just picked this bike up over the weekend. it needs some TLC. It was barley running so I changed the oil, cleaned the air filter and the carb. I have it running pretty good. The idle fluctuates and it doesnt like to idle when cold. I was going to adjust the valves as my next step. I popped off the side cover and to my supise there is an inner rotor installed on th bike. (that explines the taped up wires coming out of the case). My issue is, there does not seem to be any timing marks on the rotor!! I opened up the timing chain cover and one of the valve covers. As i rotate the engine by hand i tried to line the little circle on the timing chain sprockt with the notch on the engine. when it lines up it the engine does not feel like it is TDC on the compression stroke. when I keep rotating the engine to what feels lik TDC on the compression stroke the little circl on the sprocket is at like 5 oclock. I saw a few videos on you tube but all the bike have the standard fly wheel. Any help would be a big help. Also, What is the best gap to run? I read .005 and others run .003 on both intake and exahust. Thanks, A Newbee

[dirtbkr188]

If you remove the nut that holds the flywheel in place on the crank, you should be able to see the keyway notch on the flywheel. At TDC, with the "O" of the cam sprocket on or slightly above the mark inside the head (between the 9 and 10 o'clock position), the keyway notch should be in the same position. You could draw a straight line from the cam sprocket mark to the keyway notch, and they should all be in line with each other.

Valve adjustment for a stock head should be .002" - intake and .003" - exhaust.

At BDC, the cam sprocket "O" will be 180 degrees opposite, or in the 3 to 4 o'clock position. Since the flywheel rotates twice as much as the cam and sprocket, rotating the flywheel 1 more complete turn counterclockwise will move the cam sprocket a half-turn, to the 9-10 o'clock position.

[bill02364]

Thanks for your help on this. Bike runs great when its warm. would mocing the clip on the needle help it run better when cold? It does smoke a ton. I think a new top end over the winter. Also the timing chain is pretty loose as well.