Head gasket

Information relating to the Matchless G12 or AJS Model 31 650cc twin
MalcW
Member
Posts: 626
Joined: Tue Oct 24, 2017 12:05 pm
Location: DEVON UK

Re: Head gasket

Post by MalcW »

Groily wrote:That's reassuring to read Malc.
Neill quotes 18 for the earlier 500s, but 'tis because of the 22 in the later info for same size fasteners that I go 20 on mine.
22 is what I've done the 650 to (with copper hitherto).
After the normal re-torques and valve adjustments, hopefully all will be well for a good long time at that on composites.
I think it's the re-torquing and valve adjustment that's the critical bit, especially with the composite gaskets.

Malc
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Head gasket

Post by Groily »

Quite agree Malc. I have follow quite a strict routine for checking tightness and valve clearances:

*On final assembly
*One full heat cycle - up to running temp and then leave to go stone cold (without going anywhere)
*After 50-ish miles
*After 500-ish miles

Maybe overkill and it gets boring taking seats and tanks off . . . but seems to have been worth it over the years - and there's often a bit to do at each stage.
The 650 on copper has been the only one that leaked anything, and that was only a weep from an exhaust rocker oil feed.
If it would stop raining I'd get the 50-mile check done!
raffles
Member
Posts: 609
Joined: Mon Jan 01, 1990 12:00 am
Location: NORTHAMPTONSHIRE UK

Re: Head gasket

Post by raffles »

Bill
Lazy Iknow and every one will be up in arms BUT yes I do 28ft lbs 0n the 5/16" studs and have never in
the twenty years i have had the bike pulled down the heads after initial assembly. The engine has been
rebuilt three times.Standard when I got it, so just ran it for 18 months untill I could hear the bottom end
rattle. first rebuild after 400 miles the company that did the regrind did not as asked clean the sludge traps
journals were polished and 27,000 miles put on 3rd rebuild to stop oil leaks "O"ring conversion on oil filter
tunnel plus reface crankcases and rebore.That was two years ago and Ihave never touched the heads since
Wrong? but it works for me .Oh and those who know me will say he does the miles and dont hang about
Tony
bob121
Posts: 291
Joined: Sat Jan 14, 2017 11:48 am
Location: WEST MIDLANDS UK

Re: Head gasket

Post by bob121 »

I would say I'm guilty of over tightening the head nuts.
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