Author Topic: Gear jammed/Stuck in 2nd  (Read 1921 times)

Offline Hoff

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Gear jammed/Stuck in 2nd
« on: 10.05. 2013 09:09 »
Heres the story. Bought a '54 A10 GF plunger with an A7 engine in it. This bike hasn't been on the road since '75 so every fluid has been changed along with cables and wiring. Been riding it for approx a month ca. 7-800km and heres where it gets tricky. I went to fill her up at the gas station when suddenly the gear lever stayed down in 2nd?! i tried to force the lever up, but nothing happened. *sad2*

What could be the cause of this? i've had the front cover off the gearbox, from where i can se the selector mechanism. Still stuck and nothing to see. Only thing i did prior that day was tightening the rear chain.

Can i disassemble the rest of the gearbox while the gearbox is still on the bike? ???? If so, please explain this to a foreigner who is not that familiar with the technical terms. :!

Regards

Offline Hoff

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Re: Gear jammed/Stuck in 2nd
« Reply #1 on: 10.05. 2013 10:22 »
Heres a picture of it.

Online muskrat

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Re: Gear jammed/Stuck in 2nd
« Reply #2 on: 10.05. 2013 10:40 »
 G'day Hoff, welcome to the forum. You must have been lurking for a while, as you've put your ? in the right place  *smile*.
I would first back off the detent (under the gearbox you will see a thing 1" long with 2 flats at the end and a locknut against the case) a few turns and try again to select neutral whilst rocking the bike back & forward. It might be stuck between gears. Also try just moving the inner cover out a tad to free the claw, you may have to loosen the kick start ratchet and pinion, which will need to come off to remove the inner cover.
 I can't see the chain tension causing your problem. May be in the claw,  camplate or shift forks.
 The problem could be quite a few things. The semi unit boxes can be dismantled in the frame but can be a little tricky, like a little grub screw hiding up behind the front sprocket for the selector shaft. Parts list might help.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Online bsa-bill

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Re: Gear jammed/Stuck in 2nd
« Reply #3 on: 10.05. 2013 11:03 »
Hi Hoff (not the Hoff surely - if so hows Kit)

Just to cover first things first is the selector pawl spring (in the outer cover intact  - one leg each side of the pawl) should be but if they break they can leave you in one gear.
If you don't go wild you can put a largeish screwdriver over the stuck selector into the gearbox and gently (should I say that again) prize it down, it might free.

Not sure I agree with Musky re the chain (well he's mostly on the money), it's so easy to adjust the chain and then it find a tight spot somewhere on it's travels back and forward AND up and down, might just be enough if this occurs as your changing gear.

In any event go steady with it for a while Or have a look further inside, could be something floating about in there
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Hoff

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Re: Gear jammed/Stuck in 2nd
« Reply #4 on: 10.05. 2013 11:30 »
Thanks!

I'll try loosening the detent, i've already loosened the inner cover to try and free the claw.

The "selector pawl spring" = the two springs in the outer cover that are making sure that the lever goes back into center position after a gearchange? if so, yes they are intact and look well.

I'll give an update asap!

Offline Hoff

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Re: Gear jammed/Stuck in 2nd
« Reply #5 on: 10.05. 2013 13:03 »
Allright, i've loosened the detent and tried changing gear while wiggling the bike back and forth. No change, maybe a little more slack, but it still wont change.

What do i have to do to get the inner cover off?? (the one on the previous picture, right?)  

EDIT: Will i encounter any complications by taking the cover off whilke the bike is in 2nd gear and not neutral?

Offline Hoff

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Re: Gear jammed/Stuck in 2nd
« Reply #6 on: 10.05. 2013 14:01 »
New update! After a LOT of wiggling and loosening of the inner cover i managed to get it out of 2nd! And to be honest it seems as if nothing is wrong now. But what would you recommend i did? Just tighten it all up and continue like nothing happened, or? Im a bit concerned that the problem will just reoccur at a later stage. :-(

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Re: Gear jammed/Stuck in 2nd
« Reply #7 on: 10.05. 2013 16:20 »
 I would take the inner cover off to inspect the claw, it's spring may be weak and the teeth may chip/wear. Remove the K/S pinion nut, ratchet, pinion, spring, bush and washer. It will/should be tight to get off, use a hide mallet to tap the shafts will help. report back before going any deeper.
Cheers.
Bill, you might be right about tight spots. The plunger chains don't tighten nearly as much with wheel travel as swing arm's.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Online bsa-bill

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Re: Gear jammed/Stuck in 2nd
« Reply #8 on: 10.05. 2013 19:28 »
Quote
The plunger chains don't tighten nearly as much with wheel travel as swing arm's.

Aha, yep take your point, I must find someone near me that has a plunger.
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Hoff

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Re: Gear jammed/Stuck in 2nd
« Reply #9 on: 10.05. 2013 20:09 »
Heres an update. I reassembled the gearbox and took it for a ride. about 10 km. No weird noises from the gearbox or anything. but i noticed that the detent was far out compared to what was advised on this forum (found a topic where 1-2 treads visible from the locknut - Was more like 6-8 treads on my gearbox) so i've tightened it to about 2 threads from the locknut. Could this cause the claw or the shift forks to jump out of sync? ????

I will surely get to rebuild the gearbox, so how would you recommend i approach the task?

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Re: Gear jammed/Stuck in 2nd
« Reply #10 on: 10.05. 2013 20:39 »
 The camplate and claw arrangement can be a little temperamental especially if there's too much pressure from the detent. Going from a 20 thou to 40 thou gasket between the case and inner cover can cause problems as well, some require NO gasket to work. Who knows what the previous owner had done (stiffer spring under detent) so it's suck and see.
 If it behaves, wait till your ready to give the motor a freshen up. It's much easier with the whole lump out and box off the motor. While it's out I always replace the front sprocket and g/box seal, constant mesh gear bush's and bearing.
 When set up these g/box's are very robust.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Offline Hoff

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Re: Gear jammed/Stuck in 2nd
« Reply #11 on: 10.05. 2013 21:11 »
Ah i guess thats the beauty of these old machines. All unique and different in their own way  *smile*

The detent sort of tightens the entire arrangement that is connected to the claw in the gbox, am i right?

Do you buy a complete "kit" for rebuilding/refreshing these gboxes or do you order the needed parts individually? Do you know a store thats preferable?  ????

It's a joy actually being able to communicate and getting help and answers on a forum within minutes/hours!

Thanks!

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Re: Gear jammed/Stuck in 2nd
« Reply #12 on: 10.05. 2013 21:30 »
Yes the claw turns the camplate which moves the forks that slide the gears.
"A kit" wouldn't that be lovely, bit by bit I'm afraid. Members closer to you might suggest suppliers.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Online bsa-bill

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Re: Gear jammed/Stuck in 2nd
« Reply #13 on: 10.05. 2013 22:13 »
well done Hoff
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline fido

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Re: Gear jammed/Stuck in 2nd
« Reply #14 on: 11.05. 2013 06:45 »


The detent sort of tightens the entire arrangement that is connected to the claw in the gbox, am i right?


No, the detent works like a door latch. The camplate has notches for 1st, neutral, 2nd, 3rd and 4th and the detent drops into a notch to hold the plate and selector forks in that position so it stays in the selected gear. The gear lever and claw has just enough movement to rotate the camplate to the next detent notch.