timing gear-timing

[stirracing]

I put in a new piston and cylinder on my 400ex (416). I'm putting in the cam and getting it timed, but when I put the crankshaft to TDC I can't get the index marks on the camshaft to line up perfectly with the head the way they are supposed to, it's a little forward or a little back. Is this common and would it be better to have it forward or back? Thanks for any help.

[GPracer2500]

Go one tooth in each direction and see where the marks line up. They should be way off when you're off by one tooth. That should make it clearer as to which tooth your suppose to be on. A slightly streched cam chain will put the marks just a little off from where you might expect them to be--a whole tooth off in either direction will be obviously wrong.

[stirracing]

Thanks, I tried moving it in each direction all ready, it's just when I put in the chain tensioner it rotates the sprocket back a little. I talked to the Honda dealer today and he said a little back is better than a little foward, so I hope it's ok. Thanks again

[1fst400]

I just put my 400 motor together.


On the flywheel there are 2 marks. Put it so you are like 1mm from the first mark, Rotating counter clock wise. then you should be lined up up top.


OR, yes you want to be a little back up on the cam sprocket.


Befor you start up the motor, try turning it over with a socket. If it is wrong, well at least for me, the valves where obviously hitting the piston. take the spark plug out too, so you can tell if anything is hanging up.

[stirracing]

Thanks, I'll go turn it over by hand right now.

[bwamos]

You're being off is due to the fact that your chain stretchs a little over time.

You want to line up the cam sprocket marks as close to even with the head as possible with no slack on the front side of the chain (all slack should be on the tensioner side.. If it's a little stretched then set the cam slightly toward the rear. If it's a half tooth off, you may want a new cam chain.

[stirracing]

I bought this with the topend tore apart. I got it from a guy that works in a local shop and he said it had a new chain in it and it did have an extra chain in the box of parts. If the new chain is in there should everything be lined up perfect? Now it is exactly like you said with all the play in the back and the gear slightly toward the rear when the tensioner is tight. What can happen if the chain thats in there is streched?

[bwamos]

If it stretches too far, the metal can fatige and fail. Just like the drive chain going from your motor to the axle. Dont worry if it's like a 1/4 tooth off. I've never seen one line up perfectly. Ever. Even with a fresh chain.

[stirracing]

Thanks for letting me know that, this is pretty close so if a little off is ok I'm sure this is fine. I'm probobly being way to picky.