Cometric Gaskets
Club Member
Joined: Aug 2008
Posts: 22,849
Likes: 17,894
From: Lafayette, Louisiana
Shouldn't need to unless there are imperfections in the mating surfaces.
Coppercoat is good on head gaskets for diesels due to the extreme pressures involved.
Others will chime in with varying opinions I am sure.
Coppercoat is good on head gaskets for diesels due to the extreme pressures involved.
Others will chime in with varying opinions I am sure.
Club Member
Joined: Aug 2008
Posts: 22,849
Likes: 17,894
From: Lafayette, Louisiana
Gently heat cycle the engine several times incrementally after reassembly before getting on it. This will allow things to stretch and confirm with each other before real pressure / stress is applied.
Road Warrior
Joined: Oct 2011
Posts: 1,376
Likes: 36
From: Round Rock, TX
No, never! 
As far as break in, I use this method. Load the rings. So far so good.
http://www.mototuneusa.com/break_in_secrets.htm
As far as break in, I use this method. Load the rings. So far so good.
http://www.mototuneusa.com/break_in_secrets.htm
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
Likes: 5,449
From: la la land jerzey
i have in my shop on compression motors - i use blue hylomar sealant in a spray can and put 3 light coats and let it dry over night both sides
and a motor that has been around like some old pans and shovels never did the head gasket but did the base gaskets many times
i talked to john the owner at cometic and he gave me stuff about it but i did have a few tins leak SO
and a motor that has been around like some old pans and shovels never did the head gasket but did the base gaskets many times
i talked to john the owner at cometic and he gave me stuff about it but i did have a few tins leak SO
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Stellar HDF Member
Joined: Aug 2013
Posts: 3,425
Likes: 3,544
From: Texas
On inline 4s, I used copper coat on the base gaskets, but they were just a flat steel gasket, but I will go with just the gasket on the Harley. As far as seating the rings, I don't see that as any different than the inline fours, start it and let it run until it has warm up, shut it down and let it completely cool down, then repeat. Do that 4 time before riding.
Road Warrior
Joined: Oct 2008
Posts: 1,334
Likes: 17
From: Rosamond, Cali
It's usually a safe bet to follow the factory manual in such endeavors. The rationale being: those who design/manufacture the equipment are the experts on re-assembly procedures.
Others will have their own 'tricks', and more power to them. Perhaps they know better than the factory engineers (who are oft times constrained by the need to keep unit costs low). But generally speaking, we believe the factory on part tolerances (except .012 run-out on a twin-cam crank). So why not on re-assembly procedure?
Alan
Others will have their own 'tricks', and more power to them. Perhaps they know better than the factory engineers (who are oft times constrained by the need to keep unit costs low). But generally speaking, we believe the factory on part tolerances (except .012 run-out on a twin-cam crank). So why not on re-assembly procedure?
Alan
Last edited by AlanStansbery; Jul 8, 2016 at 08:58 PM.