Discovered Timing Marks on pinion shaft are off.

[Mag19]

Discovered timing marks are off by two teeth on pinion shaft today while putting top end together and adjusting pushrods. Picture below is showing rear cylinder at actual TDC! First time that I compare actual tdc and the timing marks. I only did a top end on this thing. Anybody got any advice here? Thanks

[kd]

It's possible the engine has rolled over backwards from valve spring pressure.  Turn the crank ahead (clockwise) 2 teeth and your marks will line up. A TDC gauge will tell you where your piston is. (or a straw in each cylinder)

[Mag19]

I did and the actual tdc in rear cylinder is where the sprockets show in the pic

[Mag19]

I did and the actual tdc in rear cylinder is where the sprockets show in the pic

Possible that I had this underlying issue all along? Ive never confirmed that actual tdc lined up with pinion shaft mark at 12 oclock

[rich1]

I would think that if the timing were off 2 teeth you would have a valve hitting a piston. Also, a compression test would show a big difference between cylinders. At least thats my thinking but I am no pro.

[rigidthumper]

Discovered timing marks are off by two teeth on pinion shaft today while putting top end together and adjusting pushrods. Picture below is showing rear cylinder at actual TDC! First time that I compare actual tdc and the timing marks. I only did a top end on this thing. Anybody got any advice here? Thanks

Back wheel off the ground, bike in hi (6th) gear. Rotate the rear wheel in a forward direction, about 10-15°, and you will see the marks line up - top dot at 6 o'clock, lower dot at 12 o'clock, cam timing looks fine to me, but rotate the assembly anyway to verify.

[BigT]

Discovered timing marks are off by two teeth on pinion shaft today while putting top end together and adjusting pushrods. Picture below is showing rear cylinder at actual TDC! First time that I compare actual tdc and the timing marks. I only did a top end on this thing. Anybody got any advice here? Thanks

Back wheel off the ground, bike in hi (6th) gear. Rotate the rear wheel in a forward direction, about 10-15°, and you will see the marks line up - top dot at 6 o'clock, lower dot at 12 o'clock, cam timing looks fine to me, but rotate the assembly anyway to verify.

I think he is comparing the timing mark position with where the piston is in the cylinder 

[Mag19]

Exactly, thats what Im doing.  Just never realized that the timing marks dont line up to actual tdc. Great trivia question lol. So far nobody has nailed it including me obviously. Gonna hit the Moco up today and get an answer.

[rigidthumper]

Remember there is TDC dwell time, so get an actual TDC stop and degree wheel, line up the dots, and remeasure.

[kd]

 

[Admiral Akbar]

Chances are, there is nothing wrong. They use the same sprocket as TCs IIRC. The flat on the pinion is matched to the crankpin.  In that case, since you not longer have a cam sitting in line with the crank, the marks had to move. RTFM, see what it says.

[ziggy24]

The crankshaft can rotate almost 20 degrees in either direction when the piston is at the top of cylinder. There is a point where the piston stops moving, and the crank assembly continues in motion until the rod begins to pull the piston back down.
Just because the piston is at the top ,it doesnt mean the crank is in TDC position. As others have said, rotate the crank, and those marks will line up. If it ran, there is certainly nothing wrong.

[Admiral Akbar]

20 degrees from TDC will put the piston 0.097 inches down in the cylinder.  If you can't see that, you need better reading glasses.  You can get within 3 to 4 degrees pretty easy.

[Hillside Motorcycle]

Degree wheel would settle any doubts.

[JW113]

Dumb question from a non-M8 owner. Does it say in TFM that there is a relationship between the cam/pinion marks, and TDC? For my lower generation bikes, there isn't....

-JW

[Goopdienes]

no it does not. im not sure why people are so worried about rear cylinder tdc and timing marks. if you follow the directions its impossible to be off. both gears are keyed!!!! line up the dots take a straight edge put it across center of cam and crank bolts. do both dots line up with straight edge. if yes your done