Compression for 800r

[p.summit]

What should the compression be for a 2008 summit xp? And what % should the 2 cylinders be within? If compression is low should i do the top end soon?

 

[flabbajabba]

I was told new should be around 140-145. Mine was 135 and 133 its 3 years old. I'd be more concerned if they were more than 5-10 apart.

 

[nielsy]

I have never seen a stock 800R with that compression130 is the high with a snap-on compression tester at 3500 feet

 

[treeboy]

Depends on what elevation you are at. Stock at sea level ive be told 150.
Myself here at 1800' I should have done a test on my new motor to see what it was at fresh. But before the new top end went in I was at 120 cold and 115 hot, starting to get alittle low I need ring but did the pistons too while I was in there.

Heres a good link talking about hot and cold compression and the fitness of the motor.
www.mxzx-revzone.com/article/engine-147.asp#compression_check

 

[p.summit]

What is the proper procedure for doing a compression test? Should the motor be cold or hot? should the throttle be held open or left alone? tryed it today and got 118 on the pto side and 119 on the other, the motor was hot.

 

[flabbajabba]

I have never seen a stock 800R with that compression130 is the high with a snap-on compression tester at 3500 feet

With 135 at Edm(2192 ft) I wouldn't be surprised to be around 130 at 3500. I've tried my tester against a Snap on and a Mac and it was bang on with them. I always test with both plugs out/WOT/ and 6 pulls.

Depends on what elevation you are at.

yeh depends on elevation I was talking about Edm with my numbers. And the 140(new motor) I got was from Specialty Sleds I told them I was checking at Edm and wanted to know if I was close. I haven't seen 140 yet out of the 4 I've checked.(stock)

 

[thumperracing]

What should the compression be for a 2008 summit xp? And what % should the 2 cylinders be within? If compression is low should i do the top end soon?

120 is good. Do a cold test with the throttle held wide open with a zip tie or elastic and give it 6 good pulls. As for side to side more than 5psi diff you should be watching it to see if it gets worse. Good luck

 

[Slytly-Stok]

Depends on what elevation you are at. Stock at sea level ive be told 150.

That is correct - I'm basically at sea level (700ft) and mine pulls 150 on the nuts, both sides. Thats on a cold motor with throttle wide open. For the heck of it, I tried it with the throttle closed and it dropped to about 142 or so.

Like other have said, I'd be more concerned with consitancy between both holes - anything more than 5psi apart from each other and I'd start keeping an eye on it....

 

[j335]

130/128 in Calgary with 5 good pulls, not wide open throttle. This is on my 08XP, cold engine.

 

[JasonT]

I was told 120 and up is pretty sold for the R.

 

[DaveB]

120 is good. Do a cold test with the throttle held wide open with a zip tie or elastic and give it 6 good pulls. As for side to side more than 5psi diff you should be watching it to see if it gets worse. Good luck

Those that do the zip-tie / elastic trick :remember to remove it!!

 

[flabbajabba]

Those that do the zip-tie / elastic trick :remember to remove it!!

Yup great advice I taped my throttle open when I shimmed my carbs and forgot to take it off I spotted it on the third pull thank goodness it didn't fire,all I could think of was the picture of sledbunny's ex-sled in the basement next door.

 

[CUSO]

Those that do the zip-tie / elastic trick :remember to remove it!!

What, people can't pull the 800 over with one hand??

 

[flabbajabba]

What, people can't pull the 800 over with one hand??

I tied my throttle to put a shim in the carbs, I found it easier to do with the slides at the top of the carb.

 

[ferniesnow]

So with 3000+ miles on 08XP with ES and motor only warm (off deck and into shop) compression on both sides was 150. Elevation is 4300'.

No throttle pull, just pushed the ES button and read the gauge.

Any suggestions from the guru's? Is the bottom end a concern and how doo I test that.

Sled is still running strong.

 

[snopro]

What, people can't pull the 800 over with one hand??

Have you seen the size of Thumper in his avatar? The pull rope is longer than he is tall! Baaahaaaawwwwaaa!

 

[snopro]

So with 3000+ miles on 08XP with ES and motor only warm (off deck and into shop) compression on both sides was 150. Elevation is 4300'.

No throttle pull, just pushed the ES button and read the gauge.

Any suggestions from the guru's? Is the bottom end a concern and how doo I test that.

Sled is still running strong.

Not a fair test Doug using the electric start unless you are trying to sell it to someome. Lol. Without actually tearing your bottom end apart to visually check the crank all you can really do is a run out test with a dial indicater.

 

[ferniesnow]

Not a fair test Doug using the electric start unless you are trying to sell it to someome. Lol. Without actually tearing your bottom end apart to visually check the crank all you can really do is a run out test with a dial indicater.

and what difference does the ES actually doo kind sir? While you are at it, what is the tolerance for the crank run out? Thanks....

 

[snopro]

and what difference does the ES actually doo kind sir? While you are at it, what is the tolerance for the crank run out? Thanks....

I've been told that you build up more compression quicker and there is no way to do a fair side to side comparison as it is hard to tell how many compression cycles you've made on each side because of the starter spinning it over so fast. Does that make any sense cause I tried to make it sound difficult. Lol. I believe the max crank runout is still around .002-.0025 if my memory serves me correct. Hope that helps ya. If you are running good oil you still got some life in her Doug.

 

[ferniesnow]

....... If you are running good oil you still got some life in her Doug.

Thanks. and I put new oil in after every ride and blow out the clutches.

Maybe another 2000+ in 'er, eh!