cold compression: what should I be getting

[mickyd32]

cold compression: what should I be getting, **now with pics

as part of my pre season checks I ran a comp test. This was cold, sled temp was at about 70 degrees when I started it prior to testing. Sled is a 13 800 RMK, approx 2300 miles

I got 101 on the clutch side and 98 on the opposite side. Seems way low to me

at any rate, its getting opened up tonight, I bought a head for it so its getting an inspection one way or another. Dealer knows as much, I told them I would report back if it was in need of some surgery, (still on warranty)

I'll post pics if I find anything note worthy

 

[theultrarider]

I tested my 11 after it had about 100 miles on it just out of curiosity. I had about 120psi on both sides. This was at about 50' of elevation. Yes. Fifty feet.

 

[mickyd32]

try not to ride into the sea at an elevation of 50 feet lol.
I'm at about 1800 feet

dealer says I should be getting 120 as well, I'll grab another tester and make sure the one I used isn't screwed

 

[Lind]

just covering all the bases here but you held the throttle wide open during test correct?

 

[Pro-8250]

I wonder if your tester is inaccurate. A difference of 3 pounds compression between the two is not terrible being that there are several variables. I do believe 120 pounds would be normal as others have stated. We are at 1400'

 

[SRXSRULE]

Compression testing..... I had a good one this summer. My race car dropped a cylinder and I did a quick compression test to try and find the cylinder. They all (v8) tested 110-120 which was low for this engine, should be 190-200.

This was with a Mac gauge set with quick change hoses for different heads. So the next day I brought home a New Mac tester from work. I just brought the gauge and used the same adapter hose I already had. Same exact results...ugh.

Just for the heck of it I tried a different adapter hose and tried it again. Shot right up to 195! Turns out the hose I was using had an internal tear in the hose and the pressure would get in that rip and seal off the hose right around the 110-120psi mark.

Long story short, always make sure your equipment is giving accurate results. Eric

 

[mickyd32]

I retested tonight. 105 105

Same tester read 120 45 on an engine that was confirmed to be screwed when we opened it up


I'm going to gety friend out with his tester tomorrow and see what he gets

And yes. Throttle wide open

 

[Snodawg]

I tested mine at 2000 miles. 1800' elevation Throttle WFO. Cold and Hot both cyls. hit 125+.

Gotta love legend oil and good engine warmups.

 

[slyrydr]

105 is definitely on the low side, and in the poo engine is indicative of a piston/ring change before the engine goes the way of all 800 poo engines...it won't be pretty..

 

[cbc24]

mines at 1000 miles and 115 psi @ 1800 ft. SO i think these engines need cyl heads

 

[mactheknife]

My 13 has 1400 miles. I tested it cold at the 1200 mile mark and got 104 and 106. Also at about 1800'. I'll try it warm in the next day or two.

Sent from my SM-N900W8 using Tapatalk

 

[m1kflyingtiger]

As stated before, seems a little low. My '11 with 11:1 turbo head ran abou 115 ish. Try put some oil in each cylander and do it again. If there's a decent bump up in compression you definatly need a refresh on the top end. If there's not a good bump...then it was a waste of a couple ounces of oil and time as it could mean great seal, or HORRIBLE seal.

 

[mickyd32]

I never got to opening it up last night. Case of beer got in the way

I will try adding some oil and see what I get

 

[gman086]

After sitting in storage all summer the rings will be very dry and adding oil should bump up those numbers so flyingtiger's suggestion is spot on. I would run to operating temp, shut down and do a "hot" check. Then wait a few hours for the "cold" check. That way the rings will be lubed and provide a more accurate reading.

Here's more info on the subject (I had the same question): http://www.snowest.com/forum/showthread.php?p=2791280

Have FUN!

G MAN

 

[mickyd32]

I have about 5 miles on the sled this year already, you would think everthing should be lubed, but I will try your suggestion

 

[mickyd32]

so I pulled the exhaust valves and did some inspecting. To me it looks like the piston is flaking all around the bottom ring. I took a few pics, best I could get with my iphone and a flashlight through the exhaust valve ports

thoughts?

It is hard to see, much easier to see when I look at it on my 60" tv than the laptop, but all around the rings you should be able to see little silver/white marks that sure do look like flaking

 

[m1kflyingtiger]

IMO some new pistons and rings aren't going to hurt.

 

[mickyd32]

I was thinking the same thing. I emailed my dealer the same pics posted here, unfortunately it was after their closing tonight. Hoping to hear from them in the morning before I make the hour drive