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Gearheadtom
06-22-2017, 06:12 PM
Any guess what caused this? I thought excessive piston to cylinder clearance causing the piston to "rock" and skirt damage, but noticed the piece gone seems to match the rod quite well. Maybe pure coincidence?
Rod bearing and wrist pin both tight. Motor was running before disassembly.
Piston skirt is scuffed bad both sides, I think dirt ingestion may have played a factor. Had only a metal screen air filter when I got it, and I figure it probably sucked a lot of dust.https://uploads.tapatalk-cdn.com/20170622/a5035dcee63e2e450007213c4e15175c.jpghttps://uploads.tapatalk-cdn.com/20170622/a2a5d67cc76ce5bf091c9101412a9a21.jpg

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BarnBoy
06-22-2017, 06:17 PM
Yikes, yeah I would say it sucked in a little dirt. I would guess that broken piece would be from piston slap.

Why did you pull it apart? Low compression? Obviously it needed to be taken apart but I am just wondering.
Gearheadtom
06-22-2017, 06:23 PM
Yikes, yeah I would say it sucked in a little dirt. I would guess that broken piece would be from piston slap.

Why did you pull it apart? Low compression? Obviously it needed to be taken apart but I am just wondering.
Smoked, and sounded bad, I thought horrible timing chain and guides, but I'm thinking now it was mostly piston slap.


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BarnBoy
06-22-2017, 06:27 PM
Oh, ok. Yeah, I think you are right. How does the cylinder look? I would assume there is a good chance it needs to be bored over based on the looks of that piston.....did you measure it yet?
Gearheadtom
06-22-2017, 06:31 PM
I've already got a .020 oversized piston waiting haha. I was expecting to bore over anyway, I pulled the head a few weeks ago to look at the piston for an oversized stamp and measured the cylinder. Still standard bore.

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barnett468
06-22-2017, 06:33 PM
see if there is aluminum from the piston in your cylinder.


PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR
Gearheadtom
06-22-2017, 06:44 PM
Looks to be a small amount of metal transfer near the bottom. Definitely seen a lot worse on snowmobile cylinders... I'm a Polaris tech by day haha

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barnett468
06-22-2017, 08:17 PM
Looks to be a small amount of metal transfer near the bottom. Definitely seen a lot worse on snowmobile cylinders... I'm a Polaris tech by day haha


can you post a photo of the end of the spark plug?

at least part of the cause of the damage is that it seized.

it is impossible for it to be so loose that the rod hit the piston.

i would just bore it out and remove the clutch cover and clean the oil filter and look for sand and metal in the oil . drag a magnet thru the oil to see what you get . maybe run some new oil in there just for around 30 minutes then drain it to try and rinse any more debris out that might be in there.
check the rocker arms and cam and cam bore in the head etc.

use good oil like mobil 1 v twin 20w-50


PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR
Gearheadtom
06-22-2017, 08:35 PM
Motor had many gasket leaks, so it was getting a complete tear down anyway. Cam and rockers looks good, very little wear.

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BarnBoy
06-22-2017, 09:31 PM
How does the rod bearing feel? Any play?
Gearheadtom
06-22-2017, 09:41 PM
No play in the rod at all.

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barnett468
06-22-2017, 09:47 PM
No play in the rod at all.


Damn, I wish I could still say that. :(



PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR
Gearheadtom
06-24-2017, 02:28 PM
I'm thinking that part of the cause was a wrist pin that began to seize. There's galling on the wrist pin. I've seen similar but worse damage on engines with completely seized wrist pins.
So I might have to send the crank away to have the rod replaced, not a shop in the city does it.

https://uploads.tapatalk-cdn.com/20170624/7a6689ea9ecf27a5e5eda01f00313ede.jpg
Gearheadtom
07-06-2017, 07:34 PM
Rod kit is ordered, and sending my crank away once I get it. CV Tech in Quebec, Canada is who I'm sending it to. We deal with them a lot at work with all the Polaris stuff and no issues.

Started stripping the bottom end, and found that piece that always breaks for the shifting (can't remember the proper name), has been "repaired" before. Looks like a bolt was cut down, and a nut was held in place with a little JB Weld haha.
https://uploads.tapatalk-cdn.com/20170706/e056fbf5b422452bcc2ea16e287b0a43.jpg

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