Does any one know the recomened tolerance for ring/cylinder wall clearance? Also witch location, on the piston, should the ring gap be facing,(i.e. "V" pattern @ 45degrees??)
Make sure the arrow on the piston points to the front, right? The piston WILL go in backwards......just won't work too well (read: not at all!)
I am not familiar with 250s, let alone '91s..but you generally are not going to be making any changes to ring gap. While you can file 4-stroke rings, you won't be doing that with 2-stroke rings cuz they are keyed (dyke sets or whatever). AND, you can't buy (that I know of) oversize rings for a 2-stroke (for you to file-to-fit).
Generally speaking, ring gap shouldn't be less than .012", piston-to-cylinder clearance not less than .0015", greater with a forged (wiseco for example) piston.
Piston-to-cylinder clearance should be measured at point of greatest wear which is the thrust surface axis (front-to-back).
Here's a complete BTW..when putting the top-end back together, put the piston (rings on, natch..pin clip on one side) in the cylinder FIRST. Then, place the cylinder/piston over the rod and put the pin in. Don't forget the other clip!!
Putting the piston on the ROD first, you have to compress the rings into the cylinder while it's attached to the rod...and that is usually tough.
Oh..make sure you have the crankcase protected (stuffed with clean rags or something). About the time a pin clip goes -sproing- into the case, you'll have a big headache.
Yea I got alot of insite from (http://ericgorr.com/)
this was my first 2-stroke rebuid.
I rode sunday to break it in & after afew miles igave it some throttle afew times. it runs great
Ialso polished the intake /exaust ports to mirror finnish. I noticed a smother Idle & acceleration but no noticeable Power. I'm thinking of a jetting /pipe change.
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