Author Topic: C14 Engine Compression  (Read 486 times)

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Offline Roger B

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C14 Engine Compression
« on: April 20, 2017, 03:15:17 am »
Curious what engine compression have some of you seen when you checked and how many miles were on it when checked?   What is the new compression psi?
Thanks.

Offline jwh20

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Re: C14 Engine Compression
« Reply #1 on: April 20, 2017, 10:13:43 am »
Compression checking is not based on the absolute measurements but the relative measurements between your cylinders.
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Offline Roger B

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Re: C14 Engine Compression
« Reply #2 on: April 20, 2017, 02:17:48 pm »
Understood, but would still like to know what numbers others have seen. I know each gauge is different. Thanks.

Offline jwh20

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Re: C14 Engine Compression
« Reply #3 on: April 20, 2017, 02:33:31 pm »
I've never done a compression check on mine.  It's usually a diagnostic procedure and I've not had any reason to run the check.  I'm not clear why anyone would run one on a new bike, it's a lot of work for minimal gain.

There is also the question of what is the normal valve clearance on a new C14 but I don't think anyone is likely to buy a new C14, ride it home, and then tear into it to check the valve clearances.
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Offline Rev Ryder

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Re: C14 Engine Compression
« Reply #4 on: April 20, 2017, 02:51:30 pm »
<SNIP> but I don't think anyone is likely to buy a new C14, ride it home, and then tear into it to check the valve clearances.

Actually, I believe one guy has done this. LOL 
Yes, I completely agree not everyone is that excited to rip apart a new machine, but when Fred Harmon, our current C-14 Tech Editor, bought one of the "then" brand spankin' new C-14s in 08, he did just that to find out what made it tick.  Even then, as you said, I don't think he did a compression check on it though as it is typically a diagnostic measure, but I wouldn't be even a little surprised if he measured the valve lash. 
Curiosity may have killed the cat, but it keeps Fred, and some other guys around here, motivated.  Totally weird... but invaluable for the rest of us.  :motonoises: 
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Offline jwh20

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Re: C14 Engine Compression
« Reply #5 on: April 20, 2017, 02:58:41 pm »
Yep that does make sense.  But I'm sure his purpose was to create material for his DVDs. 
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Offline Rev Ryder

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Re: C14 Engine Compression
« Reply #6 on: April 20, 2017, 03:09:47 pm »
In those early days, IIRC, Fred's bike was getting the plastic ripped off and put back on about every other week.  But his instructional DVDs did come in somewhere not too far down the road. Definitely within the first six months to a year I think.
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Offline Roger B

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Re: C14 Engine Compression
« Reply #7 on: April 20, 2017, 10:51:24 pm »
Has anyone checked their motor's compression and what did you find?

Offline LakeTrax

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Re: C14 Engine Compression
« Reply #8 on: April 21, 2017, 12:39:43 am »
If holding the throttle wide open like usual for a compression test, what are the secondary plates doing?

  :o

Even better question, has anyone ever done a leak-down test on the C14? :))
I need crank seals!

Offline Roger B

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Re: C14 Engine Compression
« Reply #9 on: April 21, 2017, 01:39:18 am »
Suprised no one has completed this.   Whenever I have changed plugs in bikes / snowmobiles in the past I have always checked compression while I had them out.  Especially on vehicles that are difficult to get to the plugs.  In the process of doing my valves right now and am going to check compression after completed and wanted to know what to expect.   

LakeTrax, I got your 2-stroke joke about checking the crank seals since i have replaced some of those in the past.

Offline LakeTrax

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Re: C14 Engine Compression
« Reply #10 on: April 21, 2017, 02:01:13 am »
Enough snowmobile/2-stroke work will make anybody run out and buy a leak-down tester. :truce:

You know the variances... We talking about a 5 year-old factory battery to conduct this test or a super-duper 1000 sumthing crankin' amp jumper-pack?
It's all in the details-

I bet a cold beverage that ALL new/"good running" C14s measure 148+psi on all 4 cylinders...

Lucky you if your C14 happens to be closer to 200psi and within 10% on all 4 cylinders. :beerchug:

Offline Boomer

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Re: C14 Engine Compression
« Reply #11 on: April 21, 2017, 08:22:43 pm »
From the service manual 132 to 203psi at 300rpm (starter motor speed).
George "Boomer" Garratt
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Offline MAN OF BLUES

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Re: C14 Engine Compression
« Reply #12 on: April 21, 2017, 11:16:53 pm »
Interesting...

I'll keep this in mind on my next clearance check...
Although I can see this being a lot more difficult to do on this bike, vs. A C10, reason being you could do the old girl easy with the valve cover off and plugs out...
The 14 may not co operate like that, as you need feedback from both cam position sensors to allow the starter to turn the motor over, something to think about...
If valve cover is off, intakensensor is not gonna allow the starter sequence... and spiining the engine won't occur.

Hmmmmmmm
Interesting.... and the thought of trying to get the pressure gauge threaded in for the tests on all cylinders, cramped up in that cave has me saying... I don't like at all.... :rotflmao:

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Offline Steve in Sunny Fla

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Re: C14 Engine Compression
« Reply #13 on: April 21, 2017, 11:24:52 pm »
If holding the throttle wide open like usual for a compression test, what are the secondary plates doing?

If the key is on, they're wide open.

Just guessing, but knowing the c-10's and the cam timing on the 14's I'm willing to bet cranking pressure is 190 or so.

 and the starter will turn the engine with the valve cover off. doersn't mean it gets spark, but it does turn.

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Offline MAN OF BLUES

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Re: C14 Engine Compression
« Reply #14 on: April 22, 2017, 08:14:41 pm »
If holding the throttle wide open like usual for a compression test, what are the secondary plates doing?

If the key is on, they're wide open.

Just guessing, but knowing the c-10's and the cam timing on the 14's I'm willing to bet cranking pressure is 190 or so.

 and the starter will turn the engine with the valve cover off. doersn't mean it gets spark, but it does turn.

 Steve.

Thanks for that, I never tried it, so I was just  thinking about all the "safety" features built into the electronics, and figured the starter sequence and actuation would be locked down if the cam sensor wasn't being stimulated...which would make sense...
I also agree that it would be expected to see 190 or more on a well maintained machine, with 50k or less miles...

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