I've searched the internet and this forum but couldn't find any info I'm looking for. Did anyone ever tryed to get some weigth out of the final drive? Does anyone know of someone doing it? Any picturs available? What could you take away, drill/machine/whatever?
I've seen people put holes in the aluminum housing, but i think that's more for the look than anything else. I'd imagine that one could pare some weight from the ring gear, like you would with a flywheel. That said, when I pick up a BMW final drive, I feel like it is pretty light, for what it is. Go pick up one from a Guzzi, it's much heavier, and then you'll be happier with the weight of the BMW part!
Jim Roche aka "Dr. Curve" did some lightening of his White Dog racer. Not a huge weight savings, but it is some...
The housing (is that the right name?) isn't the heavy part its the "gears" why not cut the red parts?: this isn't gonna help much but why is it here anyway? I'm sure I can get some material of the small gearing but how much will it be. Someone must have tried this before. I know about "lightweight gearboxes" (drilled holes in anything) why not the final drive
The later final drives look lighter. Just think of what would happen if your final drive locked up......declutching won't help.....
Like chasbmw says, transmissions are risky places to lighten. Weight savings is always about the sum of little bits (bites?), but in some places reliability and maintenance aren't good tradeoffs. I would want to talk to a rear end specialist prior to removing any metal. There's weight to be saved in the hub, I think.
The gears are heavy, but out of a total weight of 17 pounds they only account fo about 6 pounds, so theres a lot of metal just in the housing.
Leave off every other nut, bolt or stud. Leave out the rear brake shoes and other parts of the brakes. Leave off every other spoke on the rear wheel. Buy a skinny tire. Of course you could also buy a Honda?
The sum of parts is all in the unsprung weight. When I went from a tubed tyre to tubeless and junked the heavy duty tube on the rear wheel on my 1985 R80 monolever I threw away 3.65 lbs of weight. I would rather look at weight savings elsewhere on the bike, it can be done. R80 Monolever roadbike = 175kg dry with an empty tank (385lbs for you imperial guys) I got another 6kg to go - 169kg no fuel. However I will not be reverse engineering important mechanical bits & pieces I know not much about. If you are obsessed with weight reduction (so am I) lets start with the easy bits.
I believe the later FD's are heavier. Dr. Curve's modification is about all you can do. The gears are too hard to work with. I would leave the internal oil baffling alone. If I know Dr. Curve, that's a magnesium wheel. THAT's the solution. I wish it wasn't such a pricey solution!
Later? twin shocks vs mono arms vs para levers? Tell me more, i wanna know all I'm into offroad,. somehow I want spoke wheels in a offroad. Don't know why either.
Gjendem's bike has a lighter final drive and gearbox (and loads more). There are some pics here but they don't show the details: http://advrider.com/forums/showthread.php?t=30044 HPN has also done the same thing, there is a crappy picture of a modified gearbox somewhere at www.hpn.de
Besides, I few pounds in unsprung weight loss is like losing 50lbs elsewhere. Going on a diet? The wheels are THE place to start! It makes a HUGE difference right off the batt.
Why does it 'bother you'? They are strong enough to regularly tackle RTW trips so that's good in my eyes. In fact I've followed Dogbytes/HPN tips and actually filleted the frame, just for a bit of piece of mind, as I'm sure the bike is strong enough just for road riding. If you want a lighter bike, there are plenty of lighter Japanese bikes to choose from without going for the dodgy business of drilling holes in the final drive IMO. However I may be wrong