Help with G80 chassis strip

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Locked
joetex
Posts: 2
Joined: Tue May 22, 2018 1:45 am
Location: Dallas TX USA

Help with G80 chassis strip

Post by joetex »

I am new to the club and looking for help in the restoration of a true barn find '60 G80cs. I believe this is the year and model as the bike has a competition frame, a re-stamped motor so no ID available from the dating service, aluminum mudguard (rear only) and scrambler tires. Bike has been sitting for decades and is truly a rusty nightmare at this point. I have most of the peripheral parts off of the frame with the objective to chemical wash the frame, powder coat and re-assemble with new, old or replica parts as available. The steering lock nut and chromed cap nut are frozen. No amount of PB Blaster, WD40, etc. and elbow grease will loosen these nuts. Can anyone confirm if the cap nut is BSF or SAE (only socket close is SAE 1 5/16.) So any tricks to get these nuts loose to remove forks and triple tree, etc. from the frame? It is a duplex frame.

Any pointers in removing engine from frame? I assume primary covers (inner/outer) and clutch need to be pulled to remove transmission.

Any help with anything related to strip down of machine to frame is appreciated. Although I grew up riding BSA/Triumph, this is my first run at a Matchless and first attempt at a frame off restoration. Thanks for any suggestions, sources, etc.
User avatar
clive
Member
Posts: 5657
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: Help with G80 chassis strip

Post by clive »

hi Joe and welcome to the club. First point although I can check that you are a member it is not showing on the profile you are logged in with. This means you wi) not be able to access the whole of the site. Often happens with new members drop an email to Eamonn the web genius at webmaster@jampot.com and he will sort it.
Secondly when taking apart forks on one of my bikes the top bolt was rusted solid. A friend advised heating it up to cherry red and then allowing it to cool
This seems to break the rust and it just winds off with normal tools. You will need some sort of torch to get it all hot enough. Others may advise soaking in diesel for some weeks but the heat worked for me.
Regards
clive
if it ain't broke don't fix
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Help with G80 chassis strip

Post by Mick D »

Hi

The smaller hex is 3/4" BSW / 7/8" BSF - the larger, 7/8" BSW / 1" BSF.

If I'm not teaching you to suck eggs, try tightening the nuts to break the corrosion first, often works ;)

If not I agree with Clive - heat will be your friend, but you will need to deliver a lot of it, careful application of either oxy / acetylene or a large propane torch would be my choice.

Another option, (if you are resigned to replacing the nuts), is to MIG / TIG weld a bar to the top nut - the localised heat will break the bond and the bar can be used in lieu of a spanner to unscrew.

The archive contains the User, Parts and Workshop manuals for your bike ;)

http://archives.jampot.dk/book/

Regards Mick
56G80S
Member
Posts: 3353
Joined: Wed Oct 12, 2005 10:45 pm
Location: N YORKS UK

Re: Help with G80 chassis strip

Post by 56G80S »

If you are replacing the nuts there's always the option to cut them so that a large "C"spanner will fit. If you are referring to both the head bearing and front fork if you do cut the latter keep them - you can later use them to make up a tool to draw the fork tubes up when you re-assemble the forks. Fairly strraightforward to make a tool with a length of threaded rod.

Johnny B
joetex
Posts: 2
Joined: Tue May 22, 2018 1:45 am
Location: Dallas TX USA

Re: Help with G80 chassis strip

Post by joetex »

Thanks for the ideas. Will try the heat first and go from there.
Invicta
Member
Posts: 171
Joined: Mon Jan 29, 2018 9:42 pm
Location: Kent , England

Re: Help with G80 chassis strip

Post by Invicta »

Hi,
I had the same problem with my 1949 model 18. I could get the domed nut off but the lock nut underneath would not shift. With a socket driven over it and a large extension breaker bar all that happened was the tube that is supposed to be brazed into the lower fork crown started to turn . If you do not have access to oxyacetylene gear, which you will need to get the nuts hot enough, (forget about a blow torch that is not going to get it hot enough), or other welding gear, if you are careful you can use a fine toothed hack saw and cut vertically down the side of the nut as close as you can to the thread then using a file , file it until you can just see the thread, then using a sharp cold chisel and a lump hammer hit the nut to the side of the visible thread in an anti clockwise direction and this should shift it, as the nut should start to split and open up the thread. The nuts will be wrecked of course but if you are going to replace them anyway it won't matter. Of course if you have access to welding gear so much the better. If you are trying the heat method you will have to get them cherry red to be sure of cracking the rust.
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Help with G80 chassis strip

Post by Mick D »

Invicta wrote: (forget about a blow torch that is not going to get it hot enough)
Sorry but I have to disagree:

The frames were originally brazed / brass welded, (at red heat), which would have been carried out with gas blow torches - Sievert or Bullfinch propane torches are the modern day portable equivalent and are perfectly capable of supplying the heat required.
Torch.png
Regards Mick
You do not have the required permissions to view the files attached to this post.
Locked