Gearboxes.

Don Morris

Active Forum User
VOC Member
Robert

I have'nt been able to add any information on the Forks, but as you have the box to pieces and mentioned studs this reminded me of some of my problems with an A box.

A common mod is to fit the studs with 1/4 Whit, in the Alloy, and make the outer threads 1/4 BSF, for the nuts. This gives a better clamping force and less chance of the nut working loose. The standard is 1/4 Whit each end. Also make the studs as long as possible, in the alloy, tapping the holes if necessary. This makes the thread longer than normal and enables you to pick up on good threads.

I found it possible to increase to 5/16 two of the studs that hold the inner case of the gearchange/kickstart compartment to the gearcase proper. This helps to locate them together, and is not seen from the outside. Mine was originally rocking and fretting the mating surfaces. The best way of doing this is to put the shafts in the box, ensure they turn freely and then drill tapping size through both gearbox and inner cover. Separate and carefully enlarge the hole in the inner cover, to the stud size, this enables the new studs to act as dowels.

Another problem with mine was the kickstart return stop. This was replaced with an Socket Headed Capscrew with a special nut on the outside, special in the sense that the nut has to be reduced in diameter on its face to fit. The head of the capscrew has to be taken down a little to fit in and a short piece of hose over the head acts as a buffer.

Hope above helps and good luck, Don
 

Robert Watson

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VOC Member
Thanks Don

There were 3 stud holes in the main case that had been opened up to 5/16 tapped crooked and/or cracked through. One I retained as not too bad, and two I ground off completely and welded up, faced off in the mill and re tapped to 1/4 unc (apart from a few degrees as good as 1/4 bsw). I'll be making new studs to suit anyway. On the Twin K/S case all the 1/4 tapped holes were more or less stripped out, so I helicoiled 4 of them. The k/s stop has also had repairs so more work required there yet. Still chasing some bits but have another selector shaft on the way from the UK courtesy of a Club Member. One cover needed a clutch arm boss - it had a very loose bolt rocking around in it and that had cracked the case all around -- more welding. One had the cable boss on the k/s case missing -- more welding. I'll have a little flatening and straighteneing to do I'm sure, but in the end should have a couple of good gear boxes. The main shaft in the twin was bent .040" in the middle and worn down about .003 under the driving gear. It has been ground down and is off at the hard chromers for build up. Then I'll rebush the driving gear to suit. Lots of work. I'm making them all oiltight so I can run oil in them, so lots of holes to plug! Trouble is I have to get the whole of them put together before I know if I've done a good job!!

Cheers
 

captain vincent

Forum User
Non-VOC Member
Moose steaks

Robert,

I have a spare selector fork if you talk to me nicely and are up for a bit of Indian trading!.(moose steaks,Canadian fire water etc etc.)

Regards

Captain Vincent.
 

Robert Watson

Well Known and Active Forum User
VOC Member
Thanks for the offer. I've heard that Scots were slow to put their hand in their pocket:), but to be beaten out by a Yorkshireman!! I received one today from a very kind Member in W Yorks, so that is one more step to completion!
Robert
 

fgth130

Active Forum User
Non-VOC Member
The idea of making selector fork drawings came about after a letter in MPH earlier this year, and the drawings of the BAP selector forks have now been made. One of each fork (NOS) was put on a Mitutoyo measuring table, other examples were also measured, and the drawings were prepared.
They will be reviewed at the next Tech. Committee meeting in a few weeks time; when approved drawings are usually at the Spares Co. within 3 - 4 weeks.
 

fgth130

Active Forum User
Non-VOC Member
Forgot to mention that the drawing of 14BA has also been prepared and will be submitted for approval at the next Tech Committee meeting.
There, that'll please Robert W.
 

Robert Watson

Well Known and Active Forum User
VOC Member
Thanks Frank, I would have bought a new mainshaft fork, but my pleas have not fallen on deaf ears. I have enough now to assemble a good box for the twin plus one for the TTR that will be put together with all welded up cases and a couple of slightly loose gears, although that too will be overcome. We'll see when it is assembled if the welding has messed it up too much!

Robert
 

fgth130

Active Forum User
Non-VOC Member
Robert, the drawing of 15BA has been started, but has hit problems, because we're off to Australia for 10 weeks starting early Jan '08, the problems are retirement and time available . . . Glad to hear you located a selector fork, they're truly hen's teeth these days.
 

Robert Watson

Well Known and Active Forum User
VOC Member
Now a new issue to question. Has anyone ever done or heard of being done, a double backlash on a Burman set of gears. I seem to recall that they can be awkward sometimes, usually downshifting into second and first?? Anyone?

Robert
 
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