chain tensioner and new piston

[Skinut]

well i figured i might as well put these two questions in one post. So i want to replace my piston in my 1971 atc 90. I have a gerneral idea of how it is done but the only question i have is, do i have to take apart the cam shaft and all the valve components, becasue i am not to fimular with all that? And my other ??? was how tight should the chain be on the machine, Should i tighten the chain tensioner all the way or what? thanks guys skinut

[Skinut]

anybody with a atc 90??

[jeswinehart]

I do not have a atc 90 but do know you will hafta take the whole top end aprt to get to the piston. That includes headcap + valve cover + head and then you can slide the jug off the piston and be able to get to it for replacement.
You will not need to take the valves themselves out of where they are bolted in ,,, just remove that portion as a complete part.

Chain tension should be about a half in up and a half inch down play ,,, no tighter then. I don't run my chain driven machine that tight myself ,,, 3/4 up and down play for me.

john

[MTS]

You Have to take the motot out of the frame first (3 or 4 bolts cake) You have to pull the cam shafte out to get the cam chain off to pull the head, just make sure the lobes on the cam are pointing down or else it will hang up on the rockers and wont come loose, cam chain tension, there is a 14mm nut under the pull start if i remember correctly, while the motor is running, losen it off give the center pices (slotted) a turn untill you hear the chain stop clacking then tighten the nut back up, if it still presits to make noise there is a large nut under the motor (looks like a oil drain nut) take that off there is another adjustment, turn it in till it stops making noise.

[Skinut]

awsome guys thanks alot for the help, and info, jsut got a workshop manuel. So i am goign to attempt to do it