Gearbox modifications.

[cadastrophe]

I have decided I'm fed up with neutral between first and second gears, and will
re-mortgage my house, give away my first born child, and sell my soul in the
pursuit of having a truly sequential 'box!
Is there any reason a new selector drum couldn't be carved to this end? If so, what's involved? Anyone ever machined a selector drum?
It would make life a lot simpler and less risky for those like me who use
electric/air shifters. I have removed the neutral detent and spring to avoid
grabbing neutral when shifting by button. It makes things somewhat awkward
trying to select neutral in the pits though!

I'm not too good on gearboxes, which will explain the next
question.
Has anyone modified either 1st or top gear to act as reverse? I know some
quads have a reverse gear in a motor that's not too far removed from it's
two-wheeled-no-reverse cousins. Yet on the other hand, AFAIK, the Goldwing
has an electric reverse, which seems odd for a megalith which has everything
else under the sun fitted, and isn't apparently concerned by gross weight.
Am I right in thinking that one or more models of BMW have a reverse gear?

 

[evelrod]

I rode my first bike in 1949 and my last in 1988 so I have been away a while but in between all those years I guess I accumulated near a million miles or so. I have had all sorts of bikes with all manner of shift pattern but, one comes to mind that fits your need (???) My little Hodaka Ace 100. It had neutral at the bottom of a 5 speed. No problem on the street but in the dirt, right at the top of a hill as you went for that LAST DITCH GEAR---Guess what you got and where that put you?

Those little lights that come on in neutral are something else I have never seen a need for. You need to be smarter than the equipment you operate or else you are simply a "Motorcycle Driver" and that IMHO, is a killer.

Rod

 

[Galv]

All Kawasaki H2 750 triples shift gears the way you want so it is definately possible. The problem with a street bike is changing down and losing count of the gears and ending up in neutral, I do not know of any current bikes that shift like this. To change your shift pattern I would try brazing up the shift drum and re-machine the selector slot with milling machine and dividing-head. You may even be able to machine it with a die-grinder and carbide burr. Doing it this way gives you the chance to try the shift pattern without costing a fortune.

The problem you will have with fitting a reverse gear is finding somewhere to fit an idler shaft and gear necessary to reverse direction of the mainshaft, most of the early ATV's have a reverse stuck externaly on the side of the normal box using extended gearshafts.

Sean

 

[okeng]

Really old thread but here's an opinion anyway.

One way to theoretically get a reverse without an idler is to cut the gear teeth down and weld or braze on a couple of small sprockets and a short chain loop. I've seen some lawnmower gearboxes that looked kind of like that.

It sure seems like you should be able to rework the shift drum to make the forks do anything you want.

BTW, see if you can find some info on the Hodaka gearbox--it's really clever and totally different than normal bike transmissions. I think I've heard it referred to as a Zundapp design.

 

[evelrod]

The little Hodaka gearbox's shift mechanism was a notched rod that ran through the center of the counter gear cluster and was alternately inserted and withdrawn by a ratchet mechanism to facilitate gear selection. Each gear had a spring loaded ball and when a raised section of the shift rod lifted the ball the gear was 'locked' to the output shaft. Pretty simple, no shift forks or synchros, for a low hp light weight bike but I doubt it would be robust enough for a more powerful application.
For those who pay attention, after 15 years I bought another bike---1948 Norton---with a shift on the 'right' with a 'one up' and 'three down' pattern. I'll just get used to it I guess.

Rod

 

[okeng]

What amazed me about the Hodaka box is that the shifting mechanism seemed to take up more room than the entire 5-speed transmission. It was all outboard of the countershaft sprocket and was prone to being packed full of mud. Oddly enough, it didn't shift too well like that.

The Hodaka was a real learning experience for a 14-year old. And yes, I still have it. It's sharing chickenhouse space with a '72 husky (unrestored but rideable) and a 90% finished '67 BSA 441. At my current rate, the BSA will be complete and we can have the roll-out ceremony in 2062.

Congrats, Evelrod, on the Norton.

 

[Blackjacks]

The Hodaka set up you refer to was a Sachs design (Zundapp used Sachs engines). I had a Sachs 50 in a Casal moped. All I can say is I hope Hodaka did a better job of it.

The biggest problem with moving neutral to the bottom of the box is that 1st to neutral is half a shift. So you would not only have to remachine the grooves for the forks, but alter the pins on the end of the drum as well or you'd have trouble finding 1st, and keep hitting second.