Commando gearbox

Phil,

I must assume you don't work with the original workshop manual but with some pirate one (Haynes?). Forget them, they contain no end of misinformation. 28T is correct, and for a 750 24T for second layshaft is also correct, only late 850s had a different second gear that needs to be used in pair with the corresponding one.

Look at the gears if the are marked "AH", which means they are genuine, or unmarked or (worse?) marked "RS"- these are pirate ones. The "RS" gears were sold by W.E.Wassell in the 1980s. Apart from the questionable steel and hardening, their dogs were not undercut, hence gearboxes with these tended to jump out of gear.

The late second gear pair is marked differently- don't have one to hand right now, because I am at home, not in the shop, but I think it is "AHF" or suchlike.

Joe

The late 850 2nd gear pair are marked 'AHB' but particularly on the mainshaft gear, the third letter can be quite difficult to read.

I had this problem many years ago on my 750. I think you need to ensure that the gear is fully engaging. You may not be getting enough rotation of the selector quadrant in the outer cover to allow complete engagment. You can try loosening the retaining plate in the outer cover and moving it down before tightening again and even consider elongating the fixing holes to allow more movement in the required direction. With most of these gearboxes being 40 years old, wear between the gear change splindle and the quadrant spindle will manifest itself somwhere. If you can properly select all the gears with the outer cover removed, then the problem lies with the gubbins in the outer cover.

If you don't have a dealer close, you can buy a new layshaft 1st from Joe direct :-

http://www.nortonmotors.de/ANIL/Norton%20Website/norton/parts-list.php?pricelistpart=040115

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It was the NOC S/Hand spares that I noticed the gears for sale, so I bought a 24 tooth layshaft 2nd gear but could only see a 29 tooth 1st gear. I guess that the NOC do not stock a 28 tooth, so the next question is where can i obtain a genuine 28 tooth layshaft 1st gear, good S/Hand or new?

Recently rebuilt my gearbox, and though the bushes felt fine I replaced them as I was in there and it had done 27K. It was surprising just how worn they were when compared to new. You refer to the layshaft bearing being replaced, I read somewhere at the time that it is possible to fit a type of needle roller bearing that will have no ability to set the lateral movement of the layshaft. You may find that when you have replaced with new items from ANIL that the problem is solved. Even the bearings felt fine but being C3 spec it is hard to tell how worn they are. Also, if there has been any mis-alignment you may be able to a see a wear shine pattern on each gear tooth, caused by them being slightly offset to each other when engaged.