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Gearbox Problem 1950 Twin

notap

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VOC Member
I’m hoping I can get some advice regarding what I think is a gearbox problem on my 1950 Shadow. I have read the available literature, and I have bought a six pack of beer and sat staring at the opened kickstart cover and pondering my problem. I’m now at a bit of a dead end and suspect I will need to strip the gearbox – something I don’t want to start if it isn’t necessary.
I was replacing a worn kickstart mechanism and during the removal of the cover the spline caught on the cover and dragged the kick mechanism as well as the moveable parts of the gear change mechanism including the gear ratchet shaft (G40). I replaced all of these bits and simply slipped G40 back. All seemed okay and after a bit of filing I now have a working kickstart. However, after reassembly the bike wont go into gear – it clicks between neutral and first, but it doesn’t feel right – just a click and not a clunk! Other gears wont engage. Figuring it might be misalignment of the gear change mechanism, I removed the cover again and I also played around with the lock nuts on the battery holder. But it wasn’t like the stiffness typical of misalignment (I had that problem a few times before when I changed the kickstart return spring). Anyway I removed the cover completely and then check all the gear change mechanism (all okay). And to further eliminate further undetected problems with this mechanism I have tried changing gears with the cover off just using the gear ratchet shaft (G40) with the gear indicator lever (G81) attached for leverage. Still only clicking between neutral and first, with the clicking noise. No other gears will engage.
I have a funny feeling the problem is in the box and relates the selector cam plate? If so, can someone whose mechanical skills are limited to installing clutches etc. while sipping on beer, deal with this problem. Or is it time to seek an expert (I’m near Sydney, Australia). Any suggestions would be much appreciated. Thanks. Rob Paton
 

b'knighted

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If you are doing all of this static, without the engine running, you may not have a problem. Have you tried rotating the rear wheel or engine while trying to engage gears. Not easy with the kick start mechanism removed but maybe removing the clutch cover to rotate the primary drive will ease the gear alignment. You may need to remove the spark plugs to allow you to turn the engine by hand.
 

notap

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VOC Member
Thanks for your reply. I didn't mention that I've tried changing the gears while kicking the bike over in gear. I just temporarily attached the kickstarter. Didnt seem to make a difference. Thanks. Rob

If you are doing all of this static, without the engine running, you may not have a problem. Have you tried rotating the rear wheel or engine while trying to engage gears. Not easy with the kick start mechanism removed but maybe removing the clutch cover to rotate the primary drive will ease the gear alignment. You may need to remove the spark plugs to allow you to turn the engine by hand.
 

greg brillus

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It sounds as though you might have the G40 shaft 180 degrees out, which has put the ratchet in a possition where it cannot change gear....just a thought....Greg.
 

notap

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VOC Member
Greg, Thanks for the reply. That was my first thought too! Unfortunately not the case. Plus I did the foolproof test of only using the G40 shaft without the ratchet. I'm praying for a simple solution like this, so again thankyou! Rob

It sounds as though you might have the G40 shaft 180 degrees out, which has put the ratchet in a possition where it cannot change gear....just a thought....Greg.
 

notap

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VOC Member
Hi Ken, Yeah Ive followed those instructions to the letter, but no luck. Also, by just using G40 directly I have essentially bypassed any mistakes that may exist in the remaining components of the gear change mechanism. This is all leading me to a bad place! Thanks again. Rob

Have you read the instructions in the Rider's Handbook . There is a diagram and instructions as to how to 'time ' the assembly in 2nd gear. Ken
 

notap

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VOC Member
Greg, Only after...which makes me wonder what on earth I could have done. I can only assume that when I slipped G40 back into place it somehow dislodged something in the gearbox. Rob

Hey Rob, did it have this problem before you pulled the kickstart cover off, or only afterwards....
 

greg brillus

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VOC Member
I am going to have a stab in the dark and say that....possibly what may have happened is....uppon removing and changing/ replacing the G40 shaft, on the earlier engines ( not sure when this changed ) the bevel gear G39 AS in the roof of the gearbox had a piece of tube brazed to the outer right hand end of it, which you can see in the parts book page M 003. I have found on some engines that this tube has come loose and on odd occasions it ends up in the bottom of the gearbox where it doesn't seem to do no harm, this holds the G40 shaft in place, but can fall out if the shaft is removed, it is better to replace the early G40 shaft with the far better later type with a pin on its inner end to locate in the hole in the middle of the G39 AS bevel gear.....i'm wondering if in your case, the piece of tube has landed on top of the gear cluster, and is causing the problem you are having, perhaps it's jamming the camplate/ selector forks etc. I would pull out the G40 shaft and have a good look down the hole....perhaps find a magnet that will fit through the hole and see if you can pick it up, and shift it to a place where..as i said earlier it will do no harm untill the day you open the box and remove it....sounds extreme, but highly possible...Cheers for now....Greg.
 
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