Speedo drive nut

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Locked
Spanielsam
Posts: 86
Joined: Fri Jul 03, 2015 4:16 pm
Location: LEICS UK

Speedo drive nut

Post by Spanielsam »

Hello , another numpty question

I have just noticed that the rear wheel speedo drive is "floating" and the nut (16 in the diagram is loose)
If I tighten the nut up the speedo box wants to rotate with the wheel , with the nut loose the only thing that stops the speedo drive from rotating is the speedo cable , is this correct ?

Also for anyone who helped me with my ealier question regarding the engine "nipping" up i have now done about 40 very gentle miles without a reoccurance, so i will suck it and see

Thanks in advance
You do not have the required permissions to view the files attached to this post.
......
User avatar
thornebt
Posts: 488
Joined: Sun Apr 19, 2015 9:13 am
Location: Somerset, UK

Re: Speedo drive nut

Post by thornebt »

Spanielsam wrote:Hello , another numpty question

I have just noticed that the rear wheel speedo drive is "floating" and the nut (16 in the diagram is loose)
If I tighten the nut up the speedo box wants to rotate with the wheel , with the nut loose the only thing that stops the speedo drive from rotating is the speedo cable , is this correct ?

Also for anyone who helped me with my ealier question regarding the engine "nipping" up i have now done about 40 very gentle miles without a reoccurance, so i will suck it and see

Thanks in advance
I have had quite a few problems with speedo gearboxes. I think one of the most important things is to tighten the wheel spindle before doing up the speedo gearbox nut. Maybe it's worth loosening it all off and making sure you tighten the spindle first. I hope that helps. Cheers. Bruce.
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Speedo drive nut

Post by Mick D »

Hi

The speedo drive is retained to item 2 by the nut, in order to secure this the wheel spindle needs to be torqued up first, (with the wheel fitted to the swinging arm), you may need to grind down an open ended spanner to tighten nut 16.

Regards Mick
User avatar
ajscomboman
Member
Posts: 3963
Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: Speedo drive nut

Post by ajscomboman »

Nine times out of ten, if the speedo gearbox wants to turn with the wheel when the speedo lock nut is tightened it's because the speedo drive gearbox tangs are not located into the sots of the hub drive correctly. No it simply shouldn't just rely on the cable holding it in place. Andover Norton tried to tell me a similar thing when I was rebuilding a G15 with Norton rear wheel. Absolute cobblers!!! It transpired that their speedo gearboxes were manufactured incorrectly and it took time for me to convince them of the fact as well.
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Speedo drive nut

Post by Rob Harknett »

The speedo nut should be left loose. It cannot be tightened fully until the wheel has been fitted completely. Last of all tighten the speedo drive nut. Only if you ever need to remove the speedo drive, the very first thing to do is loosen the nut. The speedo drive will rotate freely on the wheel when not fitted in the bike. When the wheel is fitted, it should stay in the position you set it at before tightening the spindle up. If this does not happen something is wrong, so refer to comments made as Rob has done so.
Spanielsam
Posts: 86
Joined: Fri Jul 03, 2015 4:16 pm
Location: LEICS UK

Re: Speedo drive nut

Post by Spanielsam »

Thanks for all your responses, it is much appreciated

I have done as suggested, took the wheel out checked that the Dogs are engaged , re assembled , tightening the wheel spindle first and then the speedo nut and the same thing happened

Took it to bits again and it looks like the speedo gearbox housing has been squashed and so the thickness where part 2 goes through is too thin and so when i tighten the speedo nut up it is driving the dogs in too far
I have made up a washer to sit inside the speedo gearbox to effectively make the housing thicker and it works

I am sure that when i rebuilt the wheel a couple of years ago all seemed fine, i wonder if i have a " monkey metal" gearbox , it looks genuine but who knows

Does this sound like an ok fix ?
......
Locked