Crank Seals? - Snowmobile Forum: Your #1 Snowmobile Forum

jeffcool326 · 12-02-2012, 06:26 AM

What are some symptoms of bad crank seals?

**BC_Dan** · 12-02-2012, 08:33 AM

The main symptom will be a lean burn down. When the crank seal fails, it allows air to enter the crankcase. Because that air didn't come through the carbs, there's no fuel, so it dilutes (leans out) the air/fuel ratio. It can get bad enough that the lean condition causes overheating and leads to catastrophic engine failure.

It's easy to check the PTO side seal; with the engine idling, spray some wd40 or engine starter fluid on the seal area behind the primary. If there's a change in idle, the seal is allowing the fluid to enter the crankcase. The mag seal seldom fails, about the only way to check that is a leak-down test. I don't think spraying starter fluid or other material into that area would be very good for the stator.

**kccats** · 12-02-2012, 03:40 PM

High Idle is the first sign!

jeffcool326 · 12-02-2012, 04:11 PM

I'm asking this question because, I recently rebuilt my Skidoo 800. I got 2 new cylinders, new oem pistons gaskets etc.....I looked over the crank and the seals ans they were fine. I put it all back together and it starts hard. When it starts it run fine an idles fine. I am in the process of breaking it in on a stand by just warming it up and letting it air cool and then repeating the process. After it cools down it still is a bear to start. Any suggestions would be greatly appreciated......Thanks Jedf

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**kccats** · 12-03-2012, 06:27 AM

What is the compression now?

jeffcool326 · 12-03-2012, 10:50 AM

125psi in both.

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RXL · 12-03-2012, 11:48 AM

I would be having a real close look at the carb boots...

jeffcool326 · 12-04-2012, 08:16 PM

I'm beside my self right now!!! Took the carbs off and the reeds off. Re-cleaned the carbs and reed cages (vforce3) and inspected the boots everything was fine. Started hard (alot of cranking, ofcorse the carbs were empty) it fired up ran and idled fine. Shut it off and it fires right back up....shut it off for 5 minutes and it starts hard. Done a compression test 10lbs in each cylinder (WTF) Its been sitting for about 30 minutes done another compression test and I'm at 50lbs. Is this normal. These are OEM single ring pistons. Going to check compression in the morning when its cold.

**kccats** · 12-04-2012, 09:56 PM

Test at wide open throtle.

jeffcool326 · 12-05-2012, 04:42 AM

Just checked compression 50psi and 60 psi....took the head off and the cylinders look good.....Is it possible I have 2 stuck rings????

**kccats** · 12-05-2012, 06:53 AM

You could have No rings and still have 50#! Did you have any issues with the O rings? You did test at wide open throtle?

jeffcool326 · 12-05-2012, 07:37 AM

Yeah i tested at wide open......had no issues with the o rings

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RXL · 12-05-2012, 08:14 PM

Just going to throw this out there .... If you diin't put the pistons in backwards ( I'm figuring you didn't ) then you need to break it in through heat cycles on NON synthetic for a bit .. it will come up ... it will get better.

jeffcool326 · 12-05-2012, 08:53 PM

OK Can you say dumb A$$!........checked what stock psi should be and its 150psi....ok so i know something is wrong...RXL I thought the same thing too....I took apart the top end again and OMG i put the friggin rings in upside down....Made sure nothing was wrong with the pistons and the rings, Installed them the right way and put everything back together. Right away i could feel a difference just by turning the clutch. Did a compression check before anything and there it was 150psi in both. Put the plugs back in and i just hit the button and it started right up.....Let it warm up and shut it off, waited about 15mins and hit the button again and it fired right back up! As I'm putting all my tools away and cleaning up the garage i can't help but cuss myself out calling me every name in the book.....noob mechanic anyways....lol !!!! I want to thank all of you for trying to help me

.........Jeff

RXL · 12-05-2012, 08:59 PM

Just all around good stuff that it's running ... we have all done it at one time or another.

cam615 · 12-10-2012, 12:13 AM

As for the crank seal question i just wanna give BC Dan a +1. Our 03 600 wasn't idling worth a crap and really didn't run well under throttle. Took the airbox of and put my hand over the pto side carb and it would idle much better. So i sprayed brake cleaner down in where the crank seal would be and it kinda took off for a second. So after determining that as the problem tore everything down to find out that the needle in the carb on the pto side was stuck slightly open and filled the case with gas which over time got old and nasty and made the rubber seal get really mushy. I could have just about pushed through it with my fingernail. Replaced that one and the recoil side seal because why not if you have it that far apart already.
Just my experiences, BC Dan actually does know what he's talking about

meburdick · 12-10-2012, 08:32 AM

Quote:

Originally Posted by jeffcool326

OK Can you say dumb A$$!........checked what stock psi should be and its 150psi....ok so i know something is wrong...RXL I thought the same thing too....I took apart the top end again and OMG i put the friggin rings in upside down....Made sure nothing was wrong with the pistons and the rings, Installed them the right way and put everything back together. Right away i could feel a difference just by turning the clutch. Did a compression check before anything and there it was 150psi in both. Put the plugs back in and i just hit the button and it started right up.....Let it warm up and shut it off, waited about 15mins and hit the button again and it fired right back up! As I'm putting all my tools away and cleaning up the garage i can't help but cuss myself out calling me every name in the book.....noob mechanic anyways....lol !!!! I want to thank all of you for trying to help me

.........Jeff

Two ideals that I try to "live by"...

- The only stupid question is the one that you don't ask.
- The only stupid mistake is the one that you don't learn from.

You won't do this again. You're good.