Rebuilding yamaha tw125 motorcycle engine?
Answers:
Dead easy without any equipment at all.
Left hand side of bike, Cover and generator rotor off so you can see crank keyway. Line up the center of the crank, the keyway and the center of the camshaft bolt hole in a straight line and you have TDC. The camshaft cutaway at the end of the cam should be facing towards the crankshaft, you now have the correct stroke. Put the cam chain on the sprocket (fiddly this) and put the sprocket on the cam so the sprocket tang fits in the cam cutaway. The timing mark on the sprocket should be close to the timing pointer on the outside of the cam housing, above the sprocket. If it does not line up, note which direction to turn the sprocket, remove it from the cam and move the cam chain around the sprocket, one tooth at a time. Do this until the marks just about line up, refit the sprocket retaining bolt and let the cam chain adjuster take up the slack.
Recheck that the crank keyway is still perfectly aligned with the center of the cam bolt and you just timed your engine.
Works with engines from the SR, XT, TTR, and TW 125 range.
Takes less time to do than to type this.
if ur working from left side,
u want nearest piston at top and last or following piston on open fully down,.
tappets should fall into place from opposite right side if u position the turner on 45 degrees of piston.
ie pointing to 3 oclock.
Rotate the engine in the normal direction, watch the intake valve tappet, when it goes up, and then travels down, the # 1 piston is approaching TDC on the firing stroke. Rotate the engine untill the piston stops moving upward, and that is it.
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