Popping out of first on rare occasion

Well whenever I start my 73 850 Commando, on occasion it jumps out of first gear when setting off, after the inital setoff things are fine. I did research on this, and measured how much endfloat I had on my kickstarter with my dial gauge, which worked out to be around .0017. Researching the forum I found that using rear isolastic shims would take up this slack, but what would the optimum endfloat be? I am guessing between .005 and .0010 from other posts, I just want to confirm. Also, From that I can tell the shim will mate up just between where the kicker quadrant meeting the layshaft bearing, is this correct? Thanks for all the help, I know Triumph 650's pretty well, now I am learning Norton's.

My Commando used to do that occasionally until I changed the layshaft 1st gear bush that was beginning to break up and move out of position so that could be something else to check.

The hair spring in the inner case might just need a slight adjustment, Nortons seem to like a bit of endplay in everything.

This gearbox needs the layshaft to be shimmed ALA Old Britts . Use isolastic shims , trimmed or ground a bit where the correct thickness shim could hang up on reassembly .. The goal is just enough to prevent any slop , but not too tightly shimmed , to possibly prevent the kicker return to work freely .
That said after 4 Nortons , I've removed my kicker . E- start from here on in , at age 68 .
Mind you the layshaft is shimmed .
The most important thing is the roller layshaft bearing ( replacement ) . That requires the shimming , timing side .
Another factor is the first gear bush . Very small and delicate . Replace it without thinking , as all is apart . Use heat and the
frozen new bush to fit . Tap in carefully , or a light press if you have one .
Good luck , enjoy .

ashman said:

The hair spring in the inner case might just need a slight adjustment, Nortons seem to like a bit of endplay in everything.

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It was the hairpin spring on my commando when it jumped out of first gear

baz said:

It was the hairpin spring on my commando when it jumped out of first gear

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So did you just replace the spring or were you able to bend it to provide enough tension?

There should be threads on here as to how to adjust the spring.

jontg428 said:

So did you just replace the spring or were you able to bend it to provide enough tension?

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You may end up trying both
You'll need to take a look at how to set the spring correctly, some springs don't work out of the packet and others do
The problem I had from memory was that it was not going into gear fully
And then under power it would jump back out

Look at old britts gearbox assembly procedure. In the last couple of pages it talks about how to set up that spring. It's in the Resources section above.
Cheers

jontg428 said:

Researching the forum I found that using rear isolastic shims would take up this slack,

Click to expand...

I just went through this myself during gearbox re-assembly. I bought the shims Greg Marsh posted about here...


As mentioned in the Old Brits document I found that the radius at the base of the kickstart shaft held up the shim. I had to enlarge the shim inside diameter 0.040" from the supplied 1.130". So I ended up with my first shim on the kickstart shaft having an ID of 1.170".

Here is the location I placed the shim(s). I think the Old Brits document also mentioned having to place the shims into the inner case location first as the outer diameter of the shim may land on the pawl parking ramp if you try to put the shim(s) on the kickstart shaft first.









Not well seen in the above image is that the inside diamter of that shim in that first image had not been enlarged and thus it is sitting on the shaft radius, not the flat below it. Like this..





My first shim was 0.025" so enlarging the inside diameter of that first shim was enough and additional shim(s) did not require enlarging.