Gearbox selection problem

davidnewbold · Post by **davidnewbold** » Sat Jun 06, 2009 6:02 pm

Matchless 1959 G12L

Difficulty in selecting second gear from third after running for about ten miles. Symptoms are after third has been selected from fourth no resistance on gearlever other than spring pressure. Waiting a minute or going back to fourth and down again second can be selected. No other selection problems up or down. Have tried elongating selector with no effect.

TommoT · Post by **TommoT** » Sun Jun 07, 2009 10:36 am

Check the index plunger in the bottom of the gearbox. Could be a missing/destroyed index plunger or weak spring. This will prevent positive selection of one or more gears. And it's easy to take out and check from the underside.Edited by - TommoT on 07 Jun 2009 09:36:58 AM

davidnewbold · Post by **davidnewbold** » Sun Jun 07, 2009 3:51 pm

Thanks I'll give that a try

davidnewbold · Post by **davidnewbold** » Sun Jun 21, 2009 2:09 pm

Replaced the kndex plunger and spring but with no improvement anyone have any other ideas please

itma · Post by **itma** » Sun Jun 21, 2009 3:20 pm

som sticky spot in the mechanism perhaps?

Don Madden · Post by **Don Madden** » Sun Jun 21, 2009 10:16 pm

Could be a problem with the pawl spring on the selector mechanism. It looks like a hairspring with one leg crooked. The leg with crook should be away from the cover or it will select erratically.

Cheers, Don.

davidnewbold · Post by **davidnewbold** » Thu Jun 25, 2009 10:44 pm

Thanks both. The trouble started after many years of use and the gearbox hasn't been touched so I don't think it could be a reversed spring. It does feel like something sticking but the oil has been changed. Maybe I shall take it for a long ride this weekend and it will either get worse or go away.

Dave

Branston · Post by **Branston** » Sat Jun 27, 2009 5:50 pm

Hi Can you go from 3rd to 2nd ok if you very gently return the gear lever to its normal position after having come from 4th to third?
If so it sounds like the actual gear lever return spring is broken.Usually they break in such a way that it only affects gear changes going one way.
Good luck

Branston · Post by **Branston** » Sun Jun 28, 2009 12:26 pm

I just remebered I had a similar problem recently with an AMC box and assuming it was the return spring I braced myself for an oily messy gearbox outer strip-down.However I quickly discovered that the problem was caused by the gear lever not being pushed far enough onto its spline which caused the little indicator arrow to foul the clamping section of the lever.Pushed it back fully on and the selection worked perfectly!

davidnewbold · Post by **davidnewbold** » Thu Jul 02, 2009 2:39 pm

Hi Branston. Thanks for your thoughts. I have taken a look at the gear indicator and I can see no problem. Took the bike for a 50 mile ride last weekend and it was no worse (or better either) so it doesn't look as if it is going to work itself out. It is a fault that has come on without anything being touched. When I lift the pedal in fourth or second, and sometimes in third, there is immediate resistance. Mostly when I lift the pedal in third all I feel is resistance of the pedal return spring but if I keep trying I feel the resistance and it goes down to second. What I don't know is how the box registers that one down change is complete and how it resets the positive stop mechanism to prepare to go down to the next gear but this is where it seems to be failing.

Regards

David