Any body ever noticed this on a typical top end rebuild?

[modman82]

Hey guys great forum! I recently did a typical top end rebuild on my 787 in my 96 XP and found something that interested me... Have y'all ever noticed all the side to side play on the piston when fitting one to the small end of the rod? Seems like too much movement when assembled on the pin to me. Is this supposed to be correct? I can't seem to think they're going to be rocking side to side much anyway in the bores, but man they move alot on the bearing! I took a look back to the old Seadoo pistons and they were even worse than my new Wiseco set-up(2nd oversize at 82.50). Please take a look at the pictures I took of the stock Seadoo 82mm piston and my the improved forging of Wiseco's. The first should be the Wiseco and the second the Seadoo. The small end of the rod moves alot more on the Seadoo... There are other pics of me measuring as well with a digital caliper. Let me know if my concern is of any and why there is SO MUCH slack! Thanks

 

[racerxxx]

Yep, that's normal on the OEM pistons. I guess they are giving a lot of play for small assembly tolerances? If you think about it, your cylinder is going to hold it laterally. Every Bombardier I've had apart is like that. Nothing to worry about. I guess you can't use the OEM wrist pin bearings with those wiesco's? That is one of the things I really like about the late model rotax engines, more needles on the wrist pins.

 

[modman82]

Cool and ya, the new Wiseco piston kits come with rings, pins, and clips anyway. I really figured that there's not alot of side to side movement in the bore anyway. I went with the caged Wiseco bearings too. Thanks man!

 

[DSchmidt54]

Yeah , when i rebuilt out 720 in our speedster , i noticed that as well.