Snowmobile Compression Test - S2E#12
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- Опубліковано 14 лют 2016
- This video covers how - and why - to test the compression in your 2 Stroke snowmobile engine. Tested on a 1997 MXZ 670.
What is compression? What reading is optimal When should you do further investigation?f
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Please watch: "Snowmobile Track Inspection, Maintenance and Tension"
• Snowmobile Track Inspe...
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I tell you what man, I am a mechanic and I enjoy watching vids about this stuff...I just want to say that you explained this is a way that a 4 year old could understand it...nice job
+Gary Ferguson Jr Thanks Gary. Appreciate the feedback.
exceptionally well done video sir!
Thanks very much. Sorry for the delay in replies.
I would like to add that if your compression is low, you can add about a teaspoon of motor oil then redo the test...if the compression goes up then the problem is more than likely the rings...this is called a wet test...it let's you know if you need to just replace the head gasket or have to remove the jugs to inspect cylinder and replace rings...I heard you say bleed down test so I know you know this already...and I understand you are just keeping it as simple as you can...I just figured I would add this for people who wanted to go a step further...great vid man...
Great tutorial! Will benefit a lot of people.
+owenlonghorn Thanks Owen. Glad you enjoyed it.
Great video with alot of information. Thanks man.
Hey Jeremy. Glad you liked it. Thanks for taking the time to comment.
Thank you
I like your videos here from Maine
Thanks Benjamin!
Hi Dave. Great video. I checked my compression on my 98 ski doo and was glad to see 120lbs on each cylinder. Can you explain why some suggest to hold the throttle open. I don't see the relationship. Incidentally I checked mine without touching the throttle. I also have electric start. Can this test be done simply by turning it over with key and the kill switch off?
There is no need. You hear that all the time, it will make no difference to the maximum compression reached in the cylinder, I have tested that multiple times. Yes, turning it over with the starter would have the same effect.
I just put new pistons and rings in my 583 and now I have 150 in one cylinder and 120 in the other. Will they wear in with no issues or should I not run it that far apart?
Hey Dave, firstly, great video, and I just had one question. What did you do to turn the fuel off to the cylinders before you started the test? Is there a button or switch of some sort? Thanks!
Yep, the 670 has a fuel shutoff, my 600 has a flooded mode that prevents the injectors from opening
Thanks for the great info. I just bought a sled, and it runs and idles just fine. Revs up and the track moves no problem. I did a compression test with a rented gauge just out of curiosity and the reading I'm getting out of both cylinders is only 30 PSI. Am I correct in thinking that if this were true, there's no way the engine would even run? It's a 2005 Ski Doo Summit SDI 1000
Generally with much less than 100 they won’t run. If it runs an idles and moves fine, I would be wondering about the gauge
Elevation will make a big difference too. I am just above 5K feet and get a reading of 95-100 PSI (which means a new top end or some engine work) but I need to multiply that by 1.15 for my elevation to give me a sea level equivalent, Which puts me at ~115 PSI which is just fine to keep running on.
Yep, close enough. Factor .8617 so your reading x 1.1383.
Hello - I just tested my 2000 AC zr600, closed throttle, and got 90 in both cylinders. Not sure what to do next as it is obviously low. Wet test (teaspoon of oil), or leak down test?
Thats pretty low, id test it warm. You can try with throttle open and closed. At 90 id be thinking about a top end rebuild but i might check some of the forums for that sled. It must be running crappy with compression that low?
If its starting and running at 90, i might try a different guage, and if you still get 90, i think kts time for a top end.
Just bought a sled it’s a 1998 670 summit x and still holding 135 on each cylinder which I think is great paid $700 for my sled she’s mint
Hey congrats on the new sled. Hope its a good season
Is it still running good? That’s a crazy steal
What about testing a four stroke with no pull cord, Can you just crank it over with the electric start?
+Royal Productions Yes, most of the info will be the same. Should still be greater than 120, though 4 strokes can be higher. Yes you can crank it with the starter until gauge stops going up. I'd check the forums or find a service manual. Sorry, have never owned a 4 /stroke.
My Old Sled
Youre missing out ;)
is it normal that my formulax mx 1993 470 have around 140-145 of compression (equal in both cylinder) it has 2700km with original engine
Higher than I'd expect, I'd double check it, but sure.
Hi ,going to go look at a 99’ 670 mxz this weekend .The guy did the pistons and seals ,it ran then sat for a few months and he said the carb and fuel lines will need cleaning .So I doubt it runs right now as he is asking below average price . Unfortunately it has 8900 miles but I’m not afraid to put a little work in. So I wanted to run a compression test to be sure and was wondering what I could expect to get with it not being warm??
I know you do mention it’s best to test when hot as everything expands/seals but it likely won’t start .
Hmmm…maybe 110. Ill go check mine. Also check spark it wont run because of fuel lines, check spark.
I’ll check mine cold tomorrow but I think around 110 anything north of 100 should run but when you’re around the 100 range you’re probably close to a rebuild. Mostly make sure they’re pretty close to the same. Otherwise u have a problem in one cylinder
Okay sounds good , I’ll wait to hear what you come up with . Appreciate your time !
What color should your plugs be on your sled
Kinda light brown or grayish- tan on side electrode. What's up?
my old sled what can I do to fix my recoil permitly from breaking I have the same sled as you
+Caleb Austin The Recoil is pretty straight forward. I recall paisteboy has a video. In terms of fixing it permanently, everything's going to rear out eventually. The parts are all available still. What's going on with yours?
My Old Sled it was replaced but broke again it wouldn't recoil back in
Just pointing out you want to hold the throttle open when doing a compression test.
Hi Ben, I know you read that often and I do reference that in the video. The compression test measures the compression in the cylinder. There should be no difference in that value across a number of pulls regardless of throttle position. As I mention in the video, I've tried it both ways with zero difference.
I must have missed in the video, but as a rule with any gas engine you normally want the throttle open, with it closed it can actually create a vacuum when the piston is traveling down and then when it goes into the compression stroke it needs to zero out the vacuum before it even starts making positive pressure. On your sled the throttle blades on the carb or carbs may be open enough to let enough air through to not cause a problem, but lets say some one was looking at a sled that just had the carbs rebuilt and the idle wasn't set correct and the throttle was 100% closed then you would see a difference with the throttle open vs closed. Not trying to be that guy! Just another gear head putting in his .02
Oh hey...never feel like you're "that guy"! I Love the comments and people sharing their experience. Just a thought, on a 2 stroke, the piston, at its lowest point in the cycle will be below an open exhaust port, at which point the cylinder would be equalized with the ambient air pressure. The only way it would get any higher would be if it was forced in. But, on the flip side, it won't do any harm either.
I honestly spaced on the 2 cycle part, so I would agree with that. I was honestly thinking for cycle. haha, I will shut up now.
:) It's all good. Sharing is the whole point.
what product are you using to test it? a name would be great
Innova..but there are lots. Search compression tester on amazon. Very sorry for the delay.
Didn't I already see you do this video before ?
+doobyboy21 I did a compression test video on my old channel, there were a couple things I wanted to improve.
What to do if there's no fuel shut off?
Sorry I don't know how best to disable fuel on all sleds, but you don't want fuel entering the cylinder. I'd check with a dealer for your sled and ask what they suggest.
you should make you vids a little louder i love watching them and have helped me in the passed but some times when im watching on my android products i have a hard time hearing them if there's background noise in the house cheers
+matt sheffer Thanks for the feedback I'll look into it,
yes, I agree
+Gary Ferguson Jr Thanks. I picked up a new mic, hopefully the issue will improve
isnt the rotax engine a rotary engine?
+Attackofthezach Hey AOTZ - nope.
my bad, thanks for the answer lol. i have a 97 formula z 583 and one of my dads friends thought the rotax engines were rotaries
+Attackofthezach Probably thinking of the rotary valve, which opens and closes the air/fuel passage from the carb.
I have 80
What kind of sled. Hows it running?