Gearbox removal (2008)

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Per G

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Apr 7, 2008
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Had to use breakdown service last night, gears got "stiff" (but not stucked) on 2nd gear. It was in low speed and I could pull the clutch and stopped quickly. The kick was pointing towards the ground :cry:
I have had a "wining" sound on 2nd gear and was planning to do the gearbox next winter (did not get to it this winter) but obviously I need to get it down ASAP or the short riding season will be ruined :(

Time to remove the gearbox, what is the easiest way to pull the tranny?
Any special things to think of? Any high torqued nuts that needs to be loosen before other things are removed?
Would it be possible to push the gearbox maximum forward and keeping the drive side of the primary installed and only remove the clutch part?

Any advice would be highly appreciated !!!!

Best regards,
Per
 
Per G said:
The kick was pointing towards the ground
Click to expand...

That is normally an indication of layshaft bearing failure, which is reasonably common occurrence if the layshaft drive side ball bearing has not been replaced with the roller bearing (or special ball bearing)?
 
Thanks LAB!
I assume changing the bearing is best done with the gearbox removed?

Regards,
Per
 
Pull off the drive chain
Remove the clutch basket assy.
Loosen & remove clutch cable
Remove kickstart lever & outer trans cover
Loosen off nuts holding inner cover
Remove tranny from chassis
All done with removal, on to teardown...
 
Per G said:
I assume changing the bearing is best done with the gearbox removed?
Click to expand...


Yes it is, although it can be done with the gearbox in position but it is not worth the extra hassle (if you use the search facility you are likely to turn up some old gearbox & layshaft bearing discussions?).

I'm not definitely saying 100% that it is the bearing that has caused your trouble, but there's a good chance it is.

And if you have the gearbox apart, then it would certainly a good idea to change the layshaft bearings anyway, especially if the drive side one is the ball type?
 
grandpaul said:
Remove tranny from chassis
All done with removal, on to teardown...
Click to expand...

Being mindful that the cut out in the mount is usually obscured by the back of the crank case you may also need:

"remove breather stub
take rear engine mounting bolts out
shuffle engine around
graze nuckles & swear a bit"

it's all part of the fun
chris
 
Looks like I'm up for some good fun :D

The gearbox has, as far as I know, never been apart before so it's likely to be the original ball bearing still in place (or maybe not in place anymore!).
With the geaarbox removed I will most certainly take the opportunity to restore it. Looks like RGM has a "complete" overhaul kit for 75 pounds might be worth going for?

/Per
 
With a helping hand from another Commando owner the gearbox was removed today.
According to the Haynes workshop manual you should remove the center stand and the rear wheel but we did neither of it and it worked fine.

Hopefully I get time to disassemble and inspect the gearbox tomorrow.

Regards,
Per
 
Yes, it was the layshaft (ball) bearing, and it seems it hasn't damaged any other parts. I have had a "noise" on second gear and inspecting the layshaft 2nd gear confirmed the teeth being worn and I will replace it with a new set from RGM.

Regards,
Per
 
Per G, were you able to do this using Grandpaul's steps, or was there more involved?

This is one of my winter projects!
 
As far as I can remember this is the way I did it:

Pull off the drive chain.
Remove the outer primary cover, clutch basket assy, primary chain, alternator, inner primary cover, front chain sprocket.
Loosen & remove clutch cable, remove kickstart lever & gearshift lever, upper & lower gearbox mounting bolts and finally the 3 rear engine bolts.

You pull out the gearbox from the kick side but first you need to turn the gearbox counterclockwise. It doesn't come out that easy but it works :!:

I have ridden the bike 350 miles since I restored the gearbox and it runs very nice and smooth now :D

Good luck, Per
 
Per G , did you use the kit from RGM?
If so how did you go about fitting the needle roller conversion for the kickstart bush. I think this needle roller has a slightly smaller ID than the bush had, so grinding the shaft is normally required. Did you need to grind the shaft?

I have had the kit sitting here for about a month but haven't got up the gumption to tackle the job yet.
 
I did the RGM needle race conversion but let them grind the shaft which they did nicely on dia. but took too much off axially leaving part of the 1st gear bush running on nothing. With this and without a shouldered bush in the k/s for the layshaft to bear against the shaft can move quite bit. A roller bearing on the drive side lets it move freely. I replaced the roller with a high priced Hemmings 'racing' ball bearing which holds the shaft in place. It was tight fit on the journal, moreso than the regular ball bearing. So you will need to shim 1st gear to the k/s which is what RGM eventually advised me to do. Don't shim to the needle race (from the layshaft full dia.) because this can work the needle race further into the k/s. If you do press the race too far in the shaft there is little support. It's not a conversion that is straightforward in my view. Originally I did it to stop k/s movement in 1st gear (nothing to do with breaking up drive side brg.). I then found that the 2nd gear dogs on the layshaft were projecting thru the 1st gear and driving on the k/s. I had to shim behind 1st gear.
 
heat cases and fit bearings,fit 4th main&mainshaft. Now if you use the roller bearing you can press the inner race onto the layshaft and fit layshaft and gears. This process doesnot work so well with ball bearing.If the layshaft doesnt go all the way into the bearing you have no choice but to shut your eyes and try and push or tap the shaft into an un supported bearing :( I feel it would be better to fit bearing to shaft first then fit shaft gears and bearing into gearbox and then realise you cant fit gear quadrant afterwards. Then again I could have missed the whole point some where.
 
Thank you taking time to post your gearbox removal experience. I am at the "grease your bloody knuckles" stage and was hoping I did not need to remove the rear wheel - could not see any reason too. The gearbox is in tight and rotating it to the correct position looks to be the hard part. Thanks , :D
 
hello.
At my MKII from 74 I have also the shaft issue.
Today I tried even to removal the tranny, but it sticks inside the frame. I have turned the tranny ccw and then I can twist the box. But Im not able to remove out of the sub frame. The gearbox is blocked by the housing of crankshaft. I do miss 2-3 mm
Someone wrote to disassemble the 3 bolts of motor.
2 of them are screws, but at the buttom of crank housing they are thread bolts.
Do I have bend the subframe?
And then lift the motor by a jacker to get the misseing 3-5 mm
center stand I should also dissassemble isnt it?
Thanks for your support.
With best regards
Lorenz
 
Not sure of the answer...the gearbox removal process defeated me so I just pressed on with my original plan to perform the full gearbox teardown and rebuild process while still in t he bike frame. This worked out pretty well. All bearings, bushings, springs, seals replaced with new.
 
Lorenz said:
And then lift the motor by a jacker to get the misseing 3-5 mm
center stand I should also dissassemble isnt it?
Thanks for your support.
With best regards
Lorenz
Click to expand...
you can use some levers to lift the subframe to clear the bottom bolt. in the 73 they had a stud with 2 nuts = really easy to pull
don't forget to remove the right side gearbox adjusting mount, the nut on the inside will prevent you from rotating the gearbox
 
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