Newbie Questions- timing

Information relating to the Matchless G9 or AJS Model 20 500cc twin
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Newbie Questions- timing

Post by Groily »

You're well on the way then.
Dimensions of one of mine I just took out to measure - not sure if an 'original' or one I made a zillion years back, but hey, who cares? - as follows

Overall L 1.575"
Thread into mag body 0.4" long 2BA
Thread on outer end for cb cover screw 0.25" 2BA (and a bit more wouldn't hurt as you can see, for a deeper nut & washer or whatever!)
Hex section to tighten stud into mag body 0.22" at 7/32" AF (the cb dome fits over the hex section)

I said earlier the end housing was c/sunk - in fact this one is counter-bored and I use a washer od 0.32" between the hex and the housing to hold it fast. Again, not sure if it's me modding over the years, or if it's as original, but you get the drift.

So, to make one, ideally need a length of 7/32" steel hex bar, turned to major dia of 2BA as above and threaded. (Should add they don't all look exatly like this, there are those with flats milled on to do them up as I recall - but the function is the same. Loads of ways to do it, even a plain threaded stud with a 'nut' mid-point to hold the housing, if one could be filed and dressed to fit nicely.)
But try Dave Lindsley maybe as a pre-move, he might have some!
cb alloy dome stud.jpg
You do not have the required permissions to view the files attached to this post.
Sams Dad
Posts: 21
Joined: Mon Apr 19, 2021 6:49 pm
Location: Lancs UK

Re: Newbie Questions- timing

Post by Sams Dad »

Thank you once again, Groily. I have messaged Dave and hope he has them. Shane he moved from Heywood, which is about 8 miles from me lol If not, I think I could make one off your pattern.
User avatar
dave16mct
Member
Posts: 3234
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Newbie Questions- timing

Post by dave16mct »

I got a couple from Tony Cooper recently.
Tony Cooper Motorcycles
110, Olive Lane,
Halesowen,
West Midlands,
B62 8LT
Tel 0121 559 2405
Dave
Sams Dad
Posts: 21
Joined: Mon Apr 19, 2021 6:49 pm
Location: Lancs UK

Re: Newbie Questions- timing

Post by Sams Dad »

Well, I had a turn up for the books today. I found an old 2BA die and some old metal rod, which has allowed me to make the two studs for the mag housing and cover ! So hopefully tomorrow I will get it back together. Thanks for all your help. I followed your dimensions, Groily , and they fit yay. I have made up a new gasket so, subject to having cured the timing problem, I should have it back on tomorrow and be ready for another starting attempt.
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Newbie Questions- timing

Post by Groily »

Sams Dad wrote: Sat Jun 19, 2021 11:02 pm I followed your dimensions, Groily , and they fit yay.
Glad about that!! But a bit more thread on the outer end would be handy, as I said. The original nuts used were deep ones, deeper than the 5 turns of thread in the pic.
(I actually use little knurled brass 'knob-nuts' on mine so I can get the cb cover off in a hurry by hand if I ever need to, and I've modded the push button in the dome to be a carbon brush 'n spring for a remote stop button on 'bars.)
Sams Dad
Posts: 21
Joined: Mon Apr 19, 2021 6:49 pm
Location: Lancs UK

Re: Newbie Questions- timing

Post by Sams Dad »

Sorry not been back on recently. It appears the head was not torqued down properly. However, it is still letting oil out on the left cylinder head gasket The right cylinder has been getting too hot and i can't get it to run without choke. It has no air filter so I am thinking head off, new gasket, get it checked for warping and pressure tested, then skim and re -seat valves if necessary and rebuild with new gaskets. Then look at air filter and jet sugars/ needle position.
Is there anything I am missing ?
I actually rode it on choke, just on my own lane and it selected 1, 2 and 3 gears fine and pulled well but only with choke on. I am thinking right cylinder sucking air and oil leak shows it needs a head gasket so figuring do that before trying anything else.
Groily
Member
Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Newbie Questions- timing

Post by Groily »

A lot of posts on here about fitting of heads, height of spigots, thickness of gaskets etc, so worth having a rummage through older threads on here I reckon.
It's quite common for the raised spigots on the barrel face to bottom before the head gasket is compressed properly. Some gaskets have been made too thin over the years . . .
Also, beware pushrods rubbing on gaskets as they pass through (you'll see immdiately if they have!), and gaskets that 'overlap' between the cylinders and prevent good sealing - these are quite common minor nuisances too.
Also not rare to find the gaskets between inlet manifold and head(s) aren't good, and cause air leak(s). Presume carb flange not bowed, and jets and slide are to spec. A decent straight edge on the heads should give you a reasonable clue as to their flatness, if not their 'levelness'.
Locked