G12 Loss Of Power

snatchpiece · Post by **snatchpiece** » Tue Jun 26, 2007 8:49 pm

quote:

Today I rode over with my wife to see my son who lives 12 miles away, the bike ran perfectly, stayed there for an hour then returned home, again the bike ran perfectly although the speedo has now stuck at 45mph!

The speedo drive box on the rear wheel has spun round and wrapped the cable around the axle, I've twisted it back into position but how do I stop it happening again? do I tighten the 11/16 Whit nut just on the outside of the box or is it more complicated than that? is there not any locating pegs to stop it spinning? If it's stretched and snapped the cable why would the clock stick at 45mph?

Merlin · Post by **Merlin** » Tue Jun 26, 2007 9:13 pm

When this happened to my G3LS I fitted a new gearbox(speedo that is)with the help of a Northwest Member all has been well since but I do keep a close eye on it.

Biscuit · Post by **Biscuit** » Tue Jun 26, 2007 9:48 pm

You tighten the nut you refer to AFTER you have tightened the rear wheel nuts and ensuring the drive dogs are engaged with the slots in the bearing adjusting ring. The lock ring for the bearing adjusting ring must be TIGHT. If the lock ring comes loose the ring winds out and destroys the speedo gearbox.

This has happened to so many people that the mind boggles. Do a search, so much has been written on this subject.

TommoT · Post by **TommoT** » Tue Jun 26, 2007 11:31 pm

...if you follow Biscuit's advice and keep the gearbox well greased, only a breakdown of the unit itself can be disastrous!

The speedo stays at 45mph because that is the speed you were going at, when the whole thing jammed up. Without going into too much detail the speedo is chronometric, meaning that it needs to be reset between each speed measurement, and when the cable suddenly stops turning in the middle of a cycle, the needle will stay at indicated speed.

When taking everything apart you will discover that turning the cable a fraction of a turn will complete the cycle and reset the needle to zero.

Biscuit · Post by **Biscuit** » Tue Jun 26, 2007 11:44 pm

............If he hasn't ruined the gearbox and/or cable.

snatchpiece · Post by **snatchpiece** » Wed Jun 27, 2007 9:04 am

Many thanks guys, I was thinking I would need a new speedo. Sounds like I need to remove the rear wheel and check everything over. Once again, thanks for the info it's much appreciated.

griffin · Post by **griffin** » Wed Jun 27, 2007 8:05 pm

Read this first.

http://www.ajs-matchless-owners.co.uk/a ... .asp?id=57

ChrisEdited by - griffin on 27 Jun 2007 7:13:41 PMEdited by - griffin on 27 Jun 2007 9:40:12 PM

Biscuit · Post by **Biscuit** » Wed Jun 27, 2007 8:28 pm

Is that a good item to point him to?

It avoids mention of the correct order of the offside oil seal and cup, doesn't make it clear that it is the inner race that is struck to get the necessary clearance, and doesn't deal with the correct order of tightening the wheel spindle nut and the thin speedo gear box nut. Mention should also have been made of the real need to tighten the locknut on the 'speedo drive sleeve' actually adjusting ring for rear wheel bearing, really tight. Plus the need to be careful that the speedo drive dogs are correctly engaged in the slots in the bearing adjusting ring.

Crafty Chris, you slipped the second one in while I had my back turned, that one is far better. I think the first link should be ignored.
Edited by - Biscuit on 27 Jun 2007 7:32:22 PM

griffin · Post by **griffin** » Wed Jun 27, 2007 10:42 pm

Yep 1st link removed.

Crafty Chris.

snatchpiece · Post by **snatchpiece** » Thu Jun 28, 2007 9:56 am

I've been searching everywhere for info on this subject and have found a considerable amount, thanks to you guys. I have printed them all off to read at my leisure, however one item is titled 'AMC Rear Wheel Hubs' and is from 'Classic & Motorcycle Mechanics' is this the article that Chris removed from the earlier post and if so should I ignore it in case in confuses me further