G: Gearbox (Twin) Jumping out of third gear.

[Len Matthews]

Thanks everyone for your input.Ive yet to strip the box but now I know what to look for.

 

[Bill Thomas]

Instead of repositioning the fork pin I´d rather dremel the camplate, less risky for loose pins. Each fork has to be at the right spot on the cams so you can or have to do mods on the camplate only at two places, two gears for each fork. I did not do any pin repositioning but set spacers on gearshafts as good as can be done. The rest was welding and dremeling the camplate to my likings. Certainly you do this when rebuilding the engine and all can be checked while in this stage. Basically this task should not be required with a once finished engine. The weld can be seen just below the "2" and some dogleg at the opposite slot face for better engagement.

Vic

View attachment 42144

It is very hard Vic' , How did it weld ?, Cheers Bill.

 

[bmetcalf]

With the dremel, do you use a stone or carbide burr?

 

[oexing]

Welding a bit on the camplate is no big deal, I got my TIG welder out and had some high chrome rods that you get easily from Ebay or elsewhere. No need for extra hard finish as it would be brittle possibly, the chrome rods do around 55 HRC or so, even less is allright. I like that for various other places like camplate notches position lever tip, no pointy pin any more in that short bore. The point is you want low wear material as stellite will do. This is less than 60 HRC I guess but great for followers reportedly ? The Dremel tool is a grinding stone preferably, carbide is more expensive and blunt in short time, well, depends what you got at home. With all that fiddling in camplate grooves my plan was to get maximum engagement in all gears, especially with some old gears with some minor wear on dogs, was not willing to buy all new. Placing a handful of thrust washers cannot be done in all cases as you keep gears aligned and only the shifting double gears can be moved a bit more into engagement so this can be achieved ony by mods on the camplate, but I found it worthwhile - well, one of my other bikes is an Earles BMW, these are not famous for their gearboxes, not a lot of wear tolerated on driving dogs to jump out of gear - seems some sort of paranoia then . . . .

Vic

 

[litnman]

Trevor's fixture works for me. Also helps me explain to my grandsons how the gearbox functions.

 

[Bill Thomas]

As shown in my post 19,
The layshaft is a clever bit of kit !,
I also did the double backlash Racing mod' to my Twins,
That was a bit of a heart stopper !!, But works well.