Wossner Piston Clearance

tratch2 · Feb 19, 2014

Hello, i pulled apart my 2011 800 with 900 miles today because of slowly losing wot rpms and power. I found that the piston looked in great shape but was extremely loose in the cylinder and that the rings were flaking badly and ringlands extremely loose. The cylinder is perfect and has cross hatch still. Zero taper or wear at all on the cylinder. When I measured everything the wossner pistons were nearly .003 larger then the oem worn pistons and it only leaves me with .004 piston to cylinder clearance. .005 is the recommended piston/cylinder clearance from wossner. Any advise? run it with proper break in or is it to tight? Thanks!

mtncat1 · Feb 19, 2014

should be ok to run be sure your ring gap is in spec, and hone cylinders .good luck

rmscustom · Feb 19, 2014

Just curious but how did you measure your cylinders and what were the measurements?

X2 on the ring gap.

tratch2 · Feb 19, 2014

well im sure hoping it will fix all my issues im having with this sled! I cant believe with that low of miles that the pistons are in such bad shape. Ive had pump turned up from day 1 running at 50-1 ratio. The coating was still on the piston skirts even! Ive got the cylinders honed and the pistons sure fit nicely in the bore now and dosnt have half the rocking that the old pistons had. The ring gap is set at .016 spec was .012 i beleive. Has anyone done a rebuild with wossners lately? Break in procedures? heat cycle few time then on off throttle hard? First time for me running forged pistons.

tratch2 · Feb 19, 2014

I used a micrometer and bore guages, sorry i cant remeber what the measurements were. I have them written down in the shop can get the info tommrow.

rmscustom · Feb 19, 2014

Where did you get the wossners from?
That ring gap seems really tight.
I put wossners in from Rkt and ring gap spec on them was .020" I also had .005" piston to cylinder clearance.
For break in I was told varying throttle for the first 10 miles, check plugs and wash and then ride it like I stole it. I also did some heat cycles before.
With the clearance you have I might take it a little easier.

There was just a thread on here with wossners from bikeman with the ring gap set to .016" that had some cylinder problems... Not sure if the cause was ever determined but it sure looked like the rings were too tight.

tratch2 · Feb 19, 2014

I picked up the pistons from my local sled parts shop they had them in stock. The specs were right on the box. These pistons are the oem direct replacement pistons not the bmp drop in kits. Not sure if that matters or not. The ring gap said .004 though per inch of bore. The rings were .016 so i left em at that.... should i tear it back down now?

rmscustom · Feb 19, 2014

Not sure, my only experience is with my motor (800 miles this year on wossners and still going strong). You'll probably get some more opinions from people that know more than I do.

polarisperformance · Feb 19, 2014

I was at 0.016 with the durability kit with wossner piston .... finally I gap them to 0.020 cause the ring were too tight at 0.016 ....causing wear on my cylinder.
So ....gap them to 0.020 !!!

w browning · Feb 21, 2014

How did you determine they were causing excessive wear n your cylinder?

polarisperformance · Feb 21, 2014

I removed them ...scuff all around ...

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Wossner Piston Clearance

tratch2

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mtncat1

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rmscustom

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tratch2

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tratch2

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rmscustom

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tratch2

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rmscustom

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polarisperformance

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