i bought this motor from a sled dismantler, it had a melted(badly) piston, and due to the machined block he couldn't part it out, $750.
before i bought it i talked with Art, engine-tech owner, he told me where he got his pistons and that with a little machine work i'd be fine.
found a good deal on the recommended piston, so i bought two. they came and needed A LOT of machine work to match what came out. not to mention a damaged dome to replace/fix.
in searching for advice, i came across a pair of pistons, cylinders, and head w/domes, that CMX had taken off an old sled(art use to supply them w/ motors) SWEET!
put it all together. was a bit weirded out on the ring gap, it was HUGH, and piston to cyl was alot too! checked it all with the other set i had and it was the same. maybe the slop is taken up with expansion, has to be a reason for it right?
rode the sled for about 300 easy miles, was not impressed (was coming from a turbo'd 700)
then i melted a ring, took it apart and also had detn marks on the edge of piston. no problemo i had one more good piston, cylinder took it all well (no nikasiling, hardened liners). i go to 100ll mix 20%
rode for another 200 miles less easy(deeper snow) and i lose a piston! WTF
big hole right through the piston!
ok, i break down and machine the new cast pistons i had bought earlier.
and put it all together, and there is that blasted gap still, it bothers me, i don't like it!
i start it up and run around to check carb adjustments. get a nice plug reading and put it in the truck for the weekend.
then i start doing more piston to cyl. research here on snowest, read lots of posts about polaris' 800(09-on) and the fixes and the piston changes and the aftermarket pistons kits.
so i decide i will order a wiseco forged piston of the like that art recommmended. and then it gets interesting, wiseco doesn't offer that size, they offer smaller(no friggin' way) or up to 90.00mm(art recommended 85.5)
so i get the 90's thinking i'll punch the spare cylinders out for them.
when i go to see how much i need to do that the piston slides nicely in.
this is what was originally intended to go in!
i still had some work to do on the skirts (had to for the others also)
i pulled the motor apart again and did some measuring
wiseco askes for 0.004 clear i had 0.006, on one 0.007 on the other
normal ring gap is >0.02, i had 0.028 and 0.032
sweet!
ok now back to checking carb tuning
i start it up and it's idles really fast, dang what did i do?
check everything and it's all good start it back up and lower the idle set screw, it comes down nicely, that means the pistons weren't firing well at low rpm(leak down from sloppiness?)
as i recall both times it blew were when it was ridden at slow speeds.
got the jetting set for a bit rich to set pistons/rings and the thing about snaps out of your hands, and the power is instantaneous.
this is why i went to a big bore
so what did i learn?
the pistons art used were not correct.
wiseco #716m09000 are the way to go, they are for a seadoo 950 w/2.00mm overbore
also needed is a new pin bearing to convert the smaller pin to the polaris rod sized 21mmx27x25 (fits a skidoo 800)
and some machine work with a die grinder/dremel, the bearing slot on the underside of the piston needs to be widened 1mm, and the skirt needs to be shortened at least 1mm, 2 is better, i went ahead and matched the piston skirts to the liner,taking away material where the transfer ports are, don't know what this does but arts' machined pistons are this way.
i hope this saves a frustrated engine-tech owner someday. and if not i might buy your block for my other set of parts
before i bought it i talked with Art, engine-tech owner, he told me where he got his pistons and that with a little machine work i'd be fine.
found a good deal on the recommended piston, so i bought two. they came and needed A LOT of machine work to match what came out. not to mention a damaged dome to replace/fix.
in searching for advice, i came across a pair of pistons, cylinders, and head w/domes, that CMX had taken off an old sled(art use to supply them w/ motors) SWEET!
put it all together. was a bit weirded out on the ring gap, it was HUGH, and piston to cyl was alot too! checked it all with the other set i had and it was the same. maybe the slop is taken up with expansion, has to be a reason for it right?
rode the sled for about 300 easy miles, was not impressed (was coming from a turbo'd 700)
then i melted a ring, took it apart and also had detn marks on the edge of piston. no problemo i had one more good piston, cylinder took it all well (no nikasiling, hardened liners). i go to 100ll mix 20%
rode for another 200 miles less easy(deeper snow) and i lose a piston! WTF
big hole right through the piston!
ok, i break down and machine the new cast pistons i had bought earlier.
and put it all together, and there is that blasted gap still, it bothers me, i don't like it!
i start it up and run around to check carb adjustments. get a nice plug reading and put it in the truck for the weekend.
then i start doing more piston to cyl. research here on snowest, read lots of posts about polaris' 800(09-on) and the fixes and the piston changes and the aftermarket pistons kits.
so i decide i will order a wiseco forged piston of the like that art recommmended. and then it gets interesting, wiseco doesn't offer that size, they offer smaller(no friggin' way) or up to 90.00mm(art recommended 85.5)
so i get the 90's thinking i'll punch the spare cylinders out for them.
when i go to see how much i need to do that the piston slides nicely in.
this is what was originally intended to go in!
i still had some work to do on the skirts (had to for the others also)
i pulled the motor apart again and did some measuring
wiseco askes for 0.004 clear i had 0.006, on one 0.007 on the other
normal ring gap is >0.02, i had 0.028 and 0.032
sweet!
ok now back to checking carb tuning
i start it up and it's idles really fast, dang what did i do?
check everything and it's all good start it back up and lower the idle set screw, it comes down nicely, that means the pistons weren't firing well at low rpm(leak down from sloppiness?)
as i recall both times it blew were when it was ridden at slow speeds.
got the jetting set for a bit rich to set pistons/rings and the thing about snaps out of your hands, and the power is instantaneous.
this is why i went to a big bore
so what did i learn?
the pistons art used were not correct.
wiseco #716m09000 are the way to go, they are for a seadoo 950 w/2.00mm overbore
also needed is a new pin bearing to convert the smaller pin to the polaris rod sized 21mmx27x25 (fits a skidoo 800)
and some machine work with a die grinder/dremel, the bearing slot on the underside of the piston needs to be widened 1mm, and the skirt needs to be shortened at least 1mm, 2 is better, i went ahead and matched the piston skirts to the liner,taking away material where the transfer ports are, don't know what this does but arts' machined pistons are this way.
i hope this saves a frustrated engine-tech owner someday. and if not i might buy your block for my other set of parts
