1975 Commando 850 restoration

Larry S · Aug 29, 2021

The elusive fourth gear.

gortnipper · Aug 30, 2021

Larry S said:
As you suggested I leverd the quadrant into first gear, second, third and fourth. Great to confirm the camplate timing. It appears to me that my ratchet spring is not bent correctly. Does everyone agree? Hard to see but the spring is actually touching the shift pawl on both sides.

The sping shouldn't be touching the pawl.

The ratchet spring (04-0038) is bent correctly so the legs DO NOT touch the gearshift paw (04-0024), but there should be just a very small but perceptible clearance on each side.

Incorrect ratchet spring fitment.

Correct spring fitment.
Even new factory springs must be checked. It is very easy to fix a spring with the incorrect bend. Just take a pair of pliers and straighten out the legs slightly. Straighten them out a small bit at a time and keep checking until you achieve the correct fitment.
The ratchet spring must be assembled so it is flat against the ratchet plate as shown in the following picture.

The ratchet assembly.
The gearshift pawl, MUST rotate freely on the pawl pivot pin (04-0067) in order for gear change to work properly. I will normally remove the pawl, clean and polish the pin, lubricate and reassemble, to ensure free rotation.

Old Britts, Assembling the Commando gearbox

Edit: Broken link fixed

NPeteN · Aug 30, 2021

Looks like you dodged a bullet Larry.
Should be a simple fix to get you going, just click through all gears before buttoning up.

Fast Eddie · Aug 30, 2021

Larry S said:
I put the gearbox in neutral and removed the outer gearbox cover and this is the position of the shift quadrant. It appears to me that it's not in the correct position. Agreed? Off to mow my grass, will remove inner cover to check the camplate position after. Suggestions?

Yes, don’t cut it too hard at this time of year, and consider spiking.

Larry S · Aug 30, 2021

L.A.B. said:
Edit: Pic shows the oil filter housing locking plate tabs not bent up against the bolt flats.

Fixed it.

Larry S · Aug 30, 2021

Bent the ratchet spring correctly so as to not touch the gearshift pawl, put the outer cover on and went through the gears 1 thru 4. All good. Waiting for a new gasket to arrive for reassembly and test ride. Thanks for everyone’s help.

Fast Eddie · Aug 31, 2021

Larry S said:
Bent the ratchet spring correctly so as to not touch the gearshift pawl, put the outer cover on and went through the gears 1 thru 4. All good. Waiting for a new gasket to arrive for reassembly and test ride. Thanks for everyone’s help.

Good news.

And the lawn ?

NPeteN · Aug 31, 2021

Larry S said:
Bent the ratchet spring correctly so as to not touch the gearshift pawl, put the outer cover on and went through the gears 1 thru 4. All good. Waiting for a new gasket to arrive for reassembly and test ride. Thanks for everyone’s help.

ohhh you are patient!

happy riding to you.

Larry S · Aug 31, 2021

Fast Eddie said:
Good news.

And the lawn ?

The lawn has been mowed. Takes about 2 1/2 hours to mow with a zero turn mower. Fun times.

Larry S · Aug 31, 2021

NPeteN said:
ohhh you are patient!

Actually I’m a very impatient person. Working on this bike has made me much more patient what with waiting for parts and other vendors. It took me around 1 year and 4 months to get me where I’m at now so I can wait a couple more days for a new gasket. I guess. Grrrrrr!

Richard Tool · Aug 31, 2021

Almost there Larry - it will keep .

Fast Eddie · Aug 31, 2021

Larry S said:
The lawn has been mowed. Takes about 2 1/2 hours to mow with a zero turn mower. Fun times.

Mowed lawn, fixed gearbox (hopefully), you're on a roll! Buy a lottery ticket !!

Larry S · Aug 31, 2021

Fast Eddie said:
Mowed lawn, fixed gearbox (hopefully), you're on a roll! Buy a lottery ticket !!

I’ll settle for a well running/riding bike. No donation to the lottery from me.

Larry S · Sep 2, 2021

Well I reassembled the gearbox and only got 1st thru 3rd. Grrr! Off with the outer and inner covers. Before pulling the inner cover I put the quadrant in the upper most position, pulled the cover and all the gears and such. This is what I found. It looks as if the camplate and quadrant timing IS off. The index plunger is no where near the 4th gear indent on the camplate. With the inner cover off I can push the quadrant enough to click into 4th but not with the inner cover installed. The quadrant is physically stopped by the window before reaching 4th. What I plan on doing is take the camplate assembly and reset the quadrant down an appropriate amount. Need to order inner and outer gaskets and a set of Whitworth wrenches. The nut/bolt that secures the quadrant/camplate assembly is an in-between size (not 1/2 or 7/16 not 11 or 12mm) so I assume it's Whitworth.

gortnipper · Sep 2, 2021

Yep it's off. I did the same on rebuilding mine. It's PITA to go back and fix that.

These

Fiberglass reinforced silicone gaskets Archives - JS Motorsport

JS Motorsport Reusable Gaskets You can tighten them down the same as paper gaskets and they won’t squish out like regular silicone. High heat tolerant and oil tight. Sealer unnecessary

jsmotorsport.com

Larry S · Sep 2, 2021

gortnipper said:
Yep it's off. I did the same on rebuilding mine. It's PITA to go back and fix that.

These

Fiberglass reinforced silicone gaskets Archives - JS Motorsport

JS Motorsport Reusable Gaskets You can tighten them down the same as paper gaskets and they won’t squish out like regular silicone. High heat tolerant and oil tight. Sealer unnecessary

jsmotorsport.com

Too late. Just put my order in for some more paper gaskets and wrench set. Funny thing is when I disassembled the gearbox the first time I didn’t even take the cam plate assembly off the gearbox. I don’t know how the timing could have gotten off. As it is set up now there is no way possible physically to engage 4th. It seems hard to believe that the PO rode the bike with no 4th gear all that time but it is what it is.

gortnipper · Sep 2, 2021

Larry S said:
Too late. Just put my order in for some more paper gaskets and wrench set. Funny thing is when I disassembled the gearbox the first time I didn’t even take the cam plate assembly off the gearbox. I don’t know how the timing could have gotten off. As it is set up now there is no way possible physically to engage 4th. It seems hard to believe that the PO rode the bike with no 4th gear all that time but it is what it is.

It happened when you replaced the layshaft bearing. Likely knocked it a detent.

L.A.B. · Sep 3, 2021

Larry S said:
What I plan on doing is take the camplate assembly and reset the quadrant down an appropriate amount. Need to order inner and outer gaskets and a set of Whitworth wrenches. The nut/bolt that secures the quadrant/camplate assembly is an in-between size (not 1/2 or 7/16 not 11 or 12mm) so I assume it's Whitworth.

The camplate bolt hexagon should be 3/16" Whitworth or 7/16" AF (both spanners fit mine) but if the camplate is rotated past either 1st or 4th gear position (I'm not sure which) then the quadrant should drop out of mesh with the camplate which can then be retimed to the quadrant as that's the only way the quadrant could have become mistimed to the camplate without loosening the bolt and pulling the camplate out of mesh.

Larry S said:
Funny thing is when I disassembled the gearbox the first time I didn’t even take the cam plate assembly off the gearbox. I don’t know how the timing could have gotten off. As it is set up now there is no way possible physically to engage 4th. It seems hard to believe that the PO rode the bike with no 4th gear all that time but it is what it is.

The quadrant does look high (to me) in the stripdown pictures (link below) so perhaps it wasn't correct to begin with?