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xr100 timing gear

Joined
Jul 26, 2006
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#1
Hello I just overhauled a 1994 xr100r for my neighbor. the bike jumped time because of chain and gear wear. I replaced the chain and both gears,crank gear had to be cut with a die grinder and then knocked off with a chisel. Installing the new gear had to be driven on with a punch,no keyway just a press fit.reassembled entire engine.started on first kick then had an awfull rattle and quit. no compression so I removed the valve cover and the cam was not turning,upon more investigating the crank gear was spinning on the shaft. will sleeve and bearing locktight hold this on or do you think it might need a little spot weld? There is nothing that tightens against the outside of the gear just a seal next to it.
thanks confusedtech
 
Joined
Jan 27, 2000
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#2
The gear/sprocket can be held on with a couple of spots from a tig welder. Oiginally it is a interference fit of a couple thousands of an inch.

Unfortunately, you may have damaged your engine. If you did not line the press-on sprocket up properly or time the cams after you pressed the sprocket on, you may have some bent valves.

What I mean by timing the cams is to take a degree wheel and a dial indicator and check the proper opening and closing of the valves. Not just lining up the marks. Guessing or eye-balling this is not close enough. It has to be timed within a few degrees to run properly and not have the valves interfere with the piston.

When you replaced the crankshaft sprocket, you should have heated the new sprocket and frozen the end of the crankshaft before installing the new sprocket. By driving the sprocket on cold, it removed enough material from the sprocket or crank to give you a slip fit.

When you install the sprocket again, take a straight edge and align the sprocket tooth up with the crank center shaft and crank pin. The tooth should be pointing directly at the center of the crank pin. Then after aligning the cam sprocket take a dial indicator and degree wheel and check the cam timing.

If the bike still has no compression, you may have bent valves.
 
Joined
Jul 26, 2006
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#3
Thanks for the reply. Yes it did bend the exhaust valve. I went ahead and welded the gear on,and fixed the valves.
thanks confusedtech