xr100 timing gear

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.