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Bobsledder
Well-known member
Whats the thoughts on pistons and rings needing to be changed out in these engines? What mileage and should it be done based on mileage or compression?
850 Top end
- Thread starter Bobsledder
- Start date
If you are able to do regular compression tests, and it passes, then the milage hasn't worn out the parts yet.
The real issue is will YOU do the top end yourself, or be forced to schedule your sled into a shop right in the middle of the season when you could end up without the sled for weeks while you wait on parts.
If doing it yourself, order the parts and keep them on your shelf.
When she fails the compression test, YOU can do the rebuild pretty much right on the spot.
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Bobsledder
Well-known member
Would do myself. Just curious because my experience with 800HO and 800etec was crank runout was out of spec while compression was still in spec.
VALID POINT.
I haven’t seen a lot of top ends go on these 850 motors. The 19 my wife is on now went to 2900 miles no problems. With no real sign it lost a bearing in the bottom end, luckily it was still under warranty. I had a buddy do a top end last year as preventative maintenance and then he lost the same bearing in the bottom end. It was the bearing that holds the connecting rod to the crank. I’m not saying this is the case for all of them but I personally have only seen bottom end failures, there are also a few in our group that have 4-6k miles with no issues original everything.
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Bobsledder
Well-known member
I am at 2700 miles all mountain riding. Runs strong Just curious if like old two stroke thinking peple do top ends or just run em as long as compression is good
Considering most sleds probably have an hour meter, I would really be curious how many hours and miles a sled has before it needs a top end and/or crank bearings.
Doo you know what oil they were running in each case?
turbo800
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Klim
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I lost the engine in my '17 last spring at 4000 miles.
I thought it would hear the rattle signs of piston skirt collapse...nope.
Earlier in the day, ran just as good as it ever had.
It peeled the top of the piston off above the ring on the exhaust port side...at just above IDLE going down though the trees!
I agree with you, have the parts ready to go so you can minimize the downtime, if you don't already plan on doing it during the summer (recommended).
What a TESTAMENT to how well built these engines are now.
turbo800
If your not first, your last - Talladega Nights
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That's what I'm running in my turbo '17
It was a rental prior to me owning it, running XPS 2T as well.
I've always run Klotz in previous sleds, aside from the cost of XPS...I'm sold on it.
I've even switched over my oil injected Husky TE300i dirt bike from Motorex to XPS 2T.
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FlynHigh
Well-known member
In regards to a 2020 850 RMK. When pistons are replaced as a preventative measure does anything need to be done to the cylinders bores if they are in good shape? Are you guys also replacing wrist pins and wrist pin bearings? I have had a some DET codes over the years and just broke 2,000 miles so I think its time for a refresh just to be safe.
Had 2 friends this winter lose topends on turbos, both just over 5000 kms and under 6000. 1 had warranty, 1 did not and both windowed the cases. Mine has 4300 kms and will be doing mine before next season. On another note have rebuilt 2 other 850s this year due to PTO bearing failure, 1 had 1000 kms on a new long block and the other had 2200 on original motor. Lots of oil at both bearings but inner race piled up on both. No damage to rest of engine.
