Low compression 09 - iq 800 - please advise

[Mark Steffen]

I had a situation last weekend - updates all done on my 09 800 iq - bought it used, compression checked out good at purchase - 1000 miles ago. Last weekend about 30 miles into trip - mildly accelerating - approximately 5000 rpms it was liked someone hit the kill switch. Motor completely locked - pulled plugs- nice color brown. Put plugs back in and she fired right up. Ran it the rest of the day- night approx. 50 miles. The next day I burnt the chain and gears 50 miles later so my trip was done. Trip wasted - only 150 miles. Disappointed my whole family with this one.
After putting new gears and chain in yesterday I checked the compression. 105 psi in pto side - 85 psi in rt side - please advise as to what went wrong, what is wrong and a proper rebuild kit.
I have one trip planned to end the season - can I run it the way it is and tear it down later?
Please advise.
Thank you.
Mark

 

[Mark Steffen]

Have to add that I checked the compression at cold and warm engine with throttle closed. Same reading warm and cold- within a few lbs.

 

[CamoKVF700]

Cold engine. ... WOT... 5-7 pulls with both plugs out.


Sent while wishing I was on my snowbike

 

[hdkawi]

Hone the jugs and put the fix kit in


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[Vance Matheson]

I had a situation last weekend - updates all done on my 09 800 iq - bought it used, compression checked out good at purchase - 1000 miles ago. Last weekend about 30 miles into trip - mildly accelerating - approximately 5000 rpms it was liked someone hit the kill switch. Motor completely locked - pulled plugs- nice color brown. Put plugs back in and she fired right up. Ran it the rest of the day- night approx. 50 miles. The next day I burnt the chain and gears 50 miles later so my trip was done. Trip wasted - only 150 miles. Disappointed my whole family with this one.
After putting new gears and chain in yesterday I checked the compression. 105 psi in pto side - 85 psi in rt side - please advise as to what went wrong, what is wrong and a proper rebuild kit.
I have one trip planned to end the season - can I run it the way it is and tear it down later?
Please advise.
Thank you.
Mark

time for a new top end.

 

[CamoKVF700]

I tend to agree with a new top end but you have to do a child compression test with both plugs out and throttle wide open before you do anything. Below 105 isn't good. After the test you could pull the exhaust off and have a look at the pistons through the port.

Sent while wishing I was on my snowbike

 

[Mark Steffen]

Thanks guys for your comments and help,
How about this kit from erape . I ma not be keeping it but I want a quality fix. This kit seems like it has what I need. Can all of this be done with the engine in the sled.
Let me know
Thanks
Mark

 

[timbo]

Contact Shawn at PMS Polaris good guy to talk to.Yes you can replace the top end without taking out the engine.

 

[TDR]

Use one of the proven fix kits. I have done 6 MTNTK kits this year and they are all still fine. Work can be done with engine in the sled.

 

[Mark Steffen]

Okay gentlemen- more information - I have an update - please comment.
- As was suggested to me abov to retest the compression with wide open throttle- cold - so before I retested - I cleaned the exhaust valves and switched them to opposite cylinders. At wide open throttle with a cold engine I now have 100psi in the right side and 107 psi in the pto side. I feel much more comfortable with that - I am not sure my compression gauge is reading right- it could be reading low. Not sure how to calibrate the gauge. No leak down of compression in either cylinder.

I have been told that 105 psi is acceptable with no more than 10 lb difference.
I will still put the new top end on it - do I trust running it?

 

[Mark Steffen]

Next update - I was able to get 135lbs compression at an idle.
I went out today and hooked up the compression gauge to each cylinder and ran it from cold at an idle on one cylinder - each cylinder quickly hit 135 lbs compression. Dead even on both sides running on 1 and testing the other -- is this a false reading. I decided to try the single cylinder idle test as I found that if I pulled it over really hard by hand - I could get the compression to go up on both sides. I did hook up my compression gauge to my air compressor to try and calibrate it. At 110psi by air - I was 3-5 lbs short on the compression gauge.
Just a little more info.
I did use this same gauge on my 07 600 - the motor was tired - both cylinders by this gauge were 105 lbs.
Thanks for any comments and help.

 

[Mark Steffen]

Thanks Gentlemen,
After inspecting the cylinders (exhaust off) I noticed the mag side piston scuffed badly. Just installed the fix it kit with Weisco pistons and I am waiting for an intake adapter boot to fire it up.
Very disturbing to know that this went less than 800 miles on the Polaris warranty fix. I bought this used so I have no leg to stand on.
I also found that the lower ring on the mag side piston was installed over the alignment pin-- tough to know that this our dealers service at work.
Tolerances on the fix kit are much tighter- to spec- should be great- I am excited to take the final trip this weekend.
What is the breakin recommended besides adding oil to the fuel?
Thanks, all for your help.

 

[CamoKVF700]

Break in? Ummmm no. Ride it like you're going to ride it for the first little while. On and off the throttle. Don't keep a constant rpm like you would pulling a big hill. After a couple heat cycles you'll be good to go. Some will say to recheck the cylinder and head torque after a good cycle but that can be hard to get at the bolts.

Sent while wishing I was on my snowbike

 

[Mark Steffen]

Ran engine all weekend with the new update kit- 1st tank 50-1 oil added every other tank -no oil added.
Could only get 7800 rpms out of it- ran great thou. I have not done a compression test yet but I will later on in the week.
What rpms should I be turning?
It got real warm yesterday 48degrees and she didn't seem to run as good 7600 - 7700 rpms in the warm weather.

 

[Fishnuts]

Another good fix for the top end that I did was a cylinder trade through Indy Dan. He sends you his fancy welded, bored, honed cylinder and custom pistons. Very great service through him and very happy with new cylinder and pistons.
My friend had same sort of issue, sled would run good, quit at some point and be seized, free up and run again for the rest of the day. Ended up being a chunk of piston skirt in the crankcase and screwed up both bottom and top end one day.