Transmission Won't Shift

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Jan 30, 2009
I have a 1973 Commando that I bought as a partial done project. I have no history on the bike, but looks like not run in several years. The bike must have been stored inside, for it is very rust free. Have gotten the engine running reasonably well. My problem is the transmission will only shift into 1st, neutral, and 2nd gear. It will not shift into third gear. I have pulled the outer cover and the ratchet pawl and springs appear ok. I tried to move the shift arm by hand, with the same result. 1st, neutral, and 2nd, will not move into 3rd. I am not looking forward to pulling the inner cover. Anyone have any ideas before I have to disassemble the tranny.
Are you rotating the wheel as you try the gears? I had to ask just in case!
I assume it's the same with the engine running? Where does the quadrant knuckle (part projecting thru inner cover) end up in 2nd? Should be about midway and right to the top for 4th. If it's not about midway could be the PO had the box apart and didn't index the quadrant and camplate properly. If that all checks out you'll have to pull the inner cover, it's not a big job but the cover might need tapping from the rear to break free. It gets more complicated after that but with a good manual or a look at this site and go to Tech articles, How does gearbox work etc. Useful pics.
Thanks for the reply. The shift arm or quadrant knuckle is about half way in the opening in 2nd gear.
It's pretty easy to assemble the box with the quadrant off by a tooth. When it is, 1st, neutral and 2nd are easy to get, 3rd hard, and 4th impossible. If the quadrant is right, you may have a stuck gear or bent shift fork.
With the bike up on the center stand and the clutch disengaged, try moving the wheel back and forth as you shift. If you can't free up 3-4, you may have to pull the box apart.

When I put my box together, I had difficulty getting it into 3rd or 4th. I found I had assembled the quadrant one tooth off. The picture in the manual can be a little misleading. Since the quadrant is one of the first things to go in the box, all the gears have to come out. Luckily, this can be done with the box in the bike, and no need to mess with the primary. Once re-aligned, everything worked great.

Aside from assembling it wrong, I've had no issues with mine.
The arm that engages the shifting quadrant will be about 1/16" off the bottom of the window in the inner case cover if installed correctly. Similarly the same arm will be slightly tighter on the upper end of the window when in fourth gear, almost like it isn't going to allow the cover to be positioned; you play with ot a couple of times and it starts to make perfect sense.


My MkIII gear box, like everything else on the machine had sat for 27 years unmoved. Before I gave the PO the final cjeck I wanted to make sure that the engine would turn over and that the gearbox would allow for different gear selections; both passed the test, but the gearbox was super stiff, almost impossible to get into neutral from either first or second; I looked at the afterthoughtof a shit linkage and figured that more than one of the bushings would need to be replaced.

Turn the calendar ahead 3 weeks and I am stripping the bike. I pulled the gearbox out and put it on my workbench and went back to taking the bike apart. I went over to the bench to fetch a spanner and found the bench covered with water; the gearbox was full of it and the gear oil, what there was of it looked like crude oil straight form the then $140 barrel. And this on a machine with 6200 miles, kinda made my decision to NOT try and start it before working it look rather brilliant

At that point I stopped everything and hauled the gearbox into the emergency room and made it my first priority. The layshaft bearing had rusted to the point where it would not turn a full revolution and the shifting quadrant had a canal erroded dead center between first gear, through neutral and to the second gear detent; the detent plunger also had errosions to match, the poor shifting at the PO home now made perfect sense.

If your gear bushings are in passable shape rebuilding the gearbox is pretty straight forward, just remember to utilize the utility properties of hear and cold and you will not be brunelling and of your ball or roller bearings. You can make a nifty sprocket holding tool out of an old chain, the rest is super easy.

Best wishes!

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