Compression test question

[rags319]

I have a 2011 800 pro. What is the best way to test compression. Warm/Cold motor. Throttle open/closed. Put the tester on one cylinder and leave plug unplugged in other? Also what should it be for psi. Thing is starting to make alot of vibration and noise at idle. Piston slap I would think. Only has 800 miles and warranty yet this season but would like to ckeck compression
Thanks.

 

[granto]

Im not sure what the best way is but i had both plugs out, cold motor with the throttle closed and i had 120 each side. I have 1800 miles on a 12 rmk assault.

 

[Woodsrider]

Compression tests are allot like dynamo meter tests unless every thing is the same results will vary. Best is to check compression just after break in and then test the same way every time.
If you are concerned about engine condition I would pull the power valves and look at the pistons.

 

[Snodawg]

I did mine both hot and cold with no changes. 2011 Pro 800 2000 miles. Both plugs pulled, full throttle, 125 psi+ both cylinders. Altitude 1800'.

 

[4Z]

Like 'dawg, pull both plugs, screw in gauge in one hole.... pull as fast as you can, over and over, until needle stops moving up. Repeat on other hole. (you can do a warm vs. cold engine if you like)

THEN, I like to shoot some oil down the holes to seal up the rings, then repeat the above process.

Compare the two results.... if one hole is WAY different than the other, you have an issue. If wet vs. dry is WAY different, you need new rings (and might as well throw in pistons).

Please!!!! nobody ask what pistons!!!! (I always use stock ELKO pistons....... yes, ELKO still makes the OE pistons .... even though it doesn't say ELKO on them anymore )

 

[mtncat1]

Like 'dawg, pull both plugs, screw in gauge in one hole.... pull as fast as you can, over and over, until needle stops moving up. Repeat on other hole. (you can do a warm vs. cold engine if you like)

THEN, I like to shoot some oil down the holes to seal up the rings, then repeat the above process.

Compare the two results.... if one hole is WAY different than the other, you have an issue. If wet vs. dry is WAY different, you need new rings (and might as well throw in pistons).

Please!!!! nobody ask what pistons!!!! (I always use stock ELKO pistons....... yes, ELKO still makes the OE pistons .... even though it doesn't say ELKO on them anymore )

can you explain to me what you learn from doing a wet compression test on a 2stroke engine.

 

[Jay]

The oil seals the rings better than if they are dry. If you have more compression with the oil that means the rings aren't sealing as well as they should when they are dry. Your always going to have more compression with the oil, like 4Z says WAY different and you got problems. I do it the same way 4Z says except I like to give it one hard pull first and see what that one pull gives me, then I'll pull till I can't get anymore.

 

[Snodawg]

I like to give it one hard pull first and see what that one pull gives me, then I'll pull till I can't get anymore.

Classic!!! LMAO

 

[Jay]

We're still talking about compression testing here aren't we?

 

[2XM3]

Do your self a huge favor and do a leakdown test, you can buy the proper guage from summit or jegs I like the moroso one.

 

[ENDO1]

Gave it a try , have 114 pis both sides cold, 110 psi hot, is this good?
this is on a 13 RMK PRO 800, 1250 miles.

 

[TRS]

Do your self a huge favor and do a leakdown test, you can buy the proper guage from summit or jegs I like the moroso one.

Yes sir, that is the only way to get a good indication of engine condition.

Compression test does not give a true reading of engine condition. You can't compare numbers on the forum. To many variables come into play. Elevation plays a huge roll in readings (7# difference from my old dealer's shop to mine). Readings will also differ if you use a cheap walmart gauge vs. professional grade.

 

[TRS]

Classic!!! LMAO

Sorry Jay.

The wife and I are still tearing up from laughing.

 

[Jay]

Hey, if you can't laugh at yourself your taking life way to seriously. Next time I'll give it a little more thought before I hit the reply button.

 

[dyllaboy]

First take out the spark plugs, hold the throttle wide open, pull until the gauge doesn't go up anymore. It's nice to have a buddy to watch the gauge and hold the throttle. I'm at 1,200ft and my compression is 140psi in each cylinder. Stock pistons after 600 turboed miles.