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  1. #1

    kwaker js300 piston clearance

    hi all new to jet ski,s and have just been given a 86 js300 stand up ,it has had a top end failure and requires a piston kit and a rebore ,what i would like to know is the piston clearance that it will need i have ordered a 77mm kit for it and can not find any reference to piston clearance i have assumed it would be .006 would this be correct ,piston being used is a wisico cheers paul

  2. #2

    Join Date
    Apr 2006
    panama city beach 'fl
    will say on piston box

  3. #3
    If you are going to use wiseco then .006 is probably ok. I personally don't like them in 2 strokes because they are forged and expand more than a cast piston. I used to typically set mine up (cast piston) around .004. Since you have a top end failure you would be wise to disassemble the cases also. Check the crank, replace the crank seals (with a a new top end, your motor has increased crankcase pressure and vacuum and old crank seals will leak and cause another top end failure. Cheap insurance IMO

  4. #4
    thanks for that information i have already split the cases and checked out the bottom end and have new bearings and seals to put in once i get all the parts,have you had touble with wiseco pistons before bduncan as i have heard of them nipping up due to different expansion rates as compared to cast but have never had it happen on any of the bikes i have rebuilt

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