proper cylinder compression 99 Poo

indy_500

indy_500

Well-known member
I would say that's low. You want around 120 at a minimum. If my sled were to hit 110 i'd rebuild it. In the process of rebuilding an 01 doo mxz 700 right now that had 105/110. Dang 1 ring pistons!!!
 
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ezra

Well-known member
all depends on the guage I have 3 and all 3 diff lowest is 12lbs less than highest.guess witch one I bring when going to buy a used sled. but prob low at 115 and in need of a top end
 
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bartski

New member
Snodogg one thing to check woud be your clutch I have a 99 600xc and it was doggy on low end and midrange found out the clutch needed rollers and bushings (IE wasn't shifting right), just a thought
Bartski
 
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snodogg

New member
Thanks for your help guys, I asked dealer and said it should be up around 130. In hindsight I checked compression on my 09 and found it to be just under 120, so I'm thinkin' my guage reads a little low... Sending sled over to a mechanic with clutch tools to have him take a look, I think the problem mainly lies in the clutching.
 
indy_500

indy_500

Well-known member
I say anything 120+ is good, 115 is okay but 110 and under i'd rebuild. What kind of gauge do you have?
 
srt20

srt20

Active member
You do not need to worry about compression as much as you need to compare the compression between cylinders. If there is a 15% difference or more between cylinders, then its time to open the motor up. If both cylinders are very close, and compression is over 95, you arent going to gain much thats noticeable by doing the top end. On my race engines the difference between 150 and 120 is very small, like 0.4 on total compression ratio. You will not feel the difference between a 10.0 to 1 engine and a 9.5 to 1 engine. Unless maybe you are doing timed runs on ice with the exact same conditions.

Anytime a sled starts to get slower, the FIRST thing people need to look at is belt and clutch.


BTW, these cheap handheld gauges are not accurate for measuring compression on engines. They are supposed to be used to compare cylinders. You need a pump and whistler to be somewhat accurate to measure compression ratio. Or do a leakdown test.
 
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indy_500

indy_500

Well-known member
srt20 said:
You do not need to worry about compression as much as you need to compare the compression between cylinders. If there is a 15% difference or more between cylinders, then its time to open the motor up. If both cylinders are very close, and compression is over 95, you arent going to gain much thats noticeable by doing the top end. On my race engines the difference between 150 and 120 is very small, like 0.4 on total compression ratio. You will not feel the difference between a 10.0 to 1 engine and a 9.5 to 1 engine. Unless maybe you are doing timed runs on ice with the exact same conditions.

Anytime a sled starts to get slower, the FIRST thing people need to look at is belt and clutch.


BTW, these cheap handheld gauges are not accurate for measuring compression on engines. They are supposed to be used to compare cylinders. You need a pump and whistler to be somewhat accurate to measure compression ratio. Or do a leakdown test.
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I disagree. An 01 DOO 700 had 105/110 and it wouldn't go over 50 mph due to bad pistons. Finishing the rebuild on Friday, wiseco's arrived today.
 
srt20

srt20

Active member
lol, bad gas is a piss poor excuse. You mean somebody had it to lean? If it was scored bad enough that it caused that much of a performance drop, you didnt get 105psi.....just saying Indy....
 
indy_500

indy_500

Well-known member
srt20 said:
lol, bad gas is a piss poor excuse. You mean somebody had it to lean? If it was scored bad enough that it caused that much of a performance drop, you didnt get 105psi.....just saying Indy....
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My harbor freight gauge doesn't lie :p I siphoned out the gas and it didn't smell like gas at all. It was from kwik trip in case you're wondering. No air leaks. It has a can with stock jetting but shouldn't lean it out that much. It ran fine, was between E and 1/4, filled up at kwik trip, 5 miles down the trail and she ran like poop.
 
srt20

srt20

Active member
haha you crack me up. a can with stock jetting, running ethanol gas in a sled that was designed for ethanol, and you didnt figure it was too lean?? C'mon Man! The e-10 gas alone will lean it out quite a bit. And cans are worthless on snowmobiles, all they do is lean it out, make noise and lose HP. BTW Ive never had a problem with Kwik Trip gas. But my sled isnt on the ragged edge either.
 
indy_500

indy_500

Well-known member
srt20 said:
haha you crack me up. a can with stock jetting, running ethanol gas in a sled that was designed for ethanol, and you didnt figure it was too lean?? C'mon Man! The e-10 gas alone will lean it out quite a bit. And cans are worthless on snowmobiles, all they do is lean it out, make noise and lose HP. BTW Ive never had a problem with Kwik Trip gas. But my sled isnt on the ragged edge either.
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hey, it's not my sled ;)
 
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acatzl550

New member
the pistons were scored from water in the gas on the DOO 700, dealer said so when we showed them the pistons and had the cylinders honed, and also the plugs were not lean
 
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