Extra Gaskets - Snowmobile Forum: Your #1 Snowmobile Forum
User Tag List

LinkBack Thread Tools Display Modes
post #1 of 3 (permalink) Old 08-05-2019, 05:22 PM Thread Starter
Registered User
TheBearAk's Avatar
Join Date: Jan 2011
Location: North Pole, AK
Posts: 3,268
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 84 Post(s)
Extra Gaskets

Anyone who has ever rebuilt a motor has ran into the fact that most gasket kits include extras. Specially base gaskets.

So I'm working on this motor and the gasket set that came with it has 4 base gaskets. 3 of them are green and are thinner than the 4th, a black one.

Looking online, I'm seeing other gasket sets for the same cc motor either have 3 greens and no black, or 3 greens and a black.

Now, the motor I'm working on has been rebuilt before. I've been replacing every gasket and seal on a complete rebuild of this motor and was curious of how you determine which gasket(s) to use in this case. When I pulled the motor apart, it had a single green base gasket, so my thought is to use the same green base gasket.

I've heard that the reason they include more than one is to be able to shim the motor, but how do you determine if it needs shimming at all? I've never seen a motor with more than one base gasket. I've worked on probably a dozen different motors.

This motor happens to be a Skidoo 670 HO, which has a higher compression than non-HO. The gasket set for the non-HO does not come with the black gasket, which makes me wonder if I should use the black one for this as the previous rebuilder may have made a mistake.

The failure in this case was a burned up PTO piston. Like it ran lean or had a lot of pre-ignition going on (possible, because it requires 91 octane and if the previous owner put 87, it could cause this issue...at least I'm told that.)

I've not really been able to find the actual cause of the problem. PTO seal looked fine, but it did leak some oil when I poured some oil into the crankcase, which makes me thing it wasn't fine and was leaking air. I replaced the seal of course, but looking at the old seal, there are no signs of breakdown. Usually you get a spot covered with extra goo or something, but nothing, it looked brand new.

2015 Skidoo Renegade BC 600 Etec
1999 Skidoo Summit X 670 HO (Son's)
1996 Skidoo Touring E 380F (sister's)
1995 Skidoo Summit 583 LQ
1985 Skidoo Tundra 250F
1999 Arctic Cat Jag 340F
1999 Arctic Cat Z 370F (son's) - needs track
1990 Arctic Cat Jag 340F
1982 Arctic Cat Panther 440F
TheBearAk is offline  
Sponsored Links
post #2 of 3 (permalink) Old 08-06-2019, 09:14 AM
Registered User
Join Date: Sep 2018
Posts: 1,017
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 58 Post(s)
My guess is that the black may be a few thousands thinner and increasing compression.
KCCats2 is offline  
post #3 of 3 (permalink) Old 08-06-2019, 09:56 AM
Registered User
wildthangci's Avatar
Join Date: Jan 2016
Location: N. Wisconsin
Posts: 237
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
wildthangci is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Snowmobile Forum: Your #1 Snowmobile Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome