Yamaha forks on a BMW F650GS Dakar

[tomatoe333]

Originally Posted by Gangplank

Keep in mind we are talking about weight savings of the swingarm + lighter wheel, rear axel, etc.

I haven't weighed them side by side, but the rear wheel from my KTM feels about the same weight as the rear wheel from my Dakar, not counting the cush drive. Lace up an 18" rim on the BMW hub, and it's probably within a pound of the KTM part. Rear axle is heavier duty on the BMW. You _might_ be able to shave some weight there, but is it worth the risk of breakage? Remember, you've got 400 pounds of bike, give or take, to support/propel/stop/etc. The rear brake caliper is literally the same, only a mirror image, between the KTM (400 EXC) and the BMW. I can swap the pads.

I would not recommend removing the cush drive from a 650 thumper, unless you're a fan of snapped chains and holed cases. Friend had that happen on a Husky TE610, with some very unhappy results.

[swamp]

where are you guys ordering the longer front brake line?
does it come with the connectors?

danks

[Gangplank]

Originally Posted by swamp

where are you guys ordering the longer front brake line?
does it come with the connectors?

danks

Is the longer front brake line needed if you are using the YZ250 forks and brakes?

[tomatoe333]

Originally Posted by Gangplank

Is the longer front brake line needed if you are using the YZ250 forks and brakes?

You can use a "standard" YZ250 brake line if you've swapped over the Yamaha brakes.

[GSBS]

Originally Posted by tomatoe333

You can use a "standard" YZ250 brake line if you've swapped over the Yamaha brakes.

I used the YZ forks, wheel, brake caliper and disc, but kept the BMW master cylinder assembly on the handlebars. Trouble was there were two sizes of banjo bolt fittings for the brake line at each end.

I ordered a "universal" line which is threaded at each end and then the correct size threaded banjo bolts for caliper and master cylinder to screw onto the new line. I think it was $40-50. Has worked with no issues in nearly 12K miles.

[Aquatic]

Originally Posted by LoJack

I'd still be interested in replacing it if I knew what to look for.

https://www.dropbox.com/s/bt4rv9rt1o...WING%20ARM.PDF

[LoJack]

Originally Posted by Aquatic

https://www.dropbox.com/s/bt4rv9rt1o...WING%20ARM.PDF

You were nice enough to send me that a number of months ago. I still have it. I have been learning Solid Works and have been wanting to draw it in there. I need to get a better computer, though. My laptop blows for SW. I've been looking at towers but am not sure yet about a graphics card.

A year or so ago a friend that works with SW was helping me model a swing arm that had arms fully machined out of billet that had a lattice structure for strength. It was wicked cool looking but I realized it would cost about a grand to have the arms machined. That, and the more I learned about aluminum, the less I realized I knew. That's partly what prompted me to go back to school.

[dwayne]

Originally Posted by tomatoe333

I haven't weighed them side by side, but the rear wheel from my KTM feels about the same weight as the rear wheel from my Dakar, not counting the cush drive. Lace up an 18" rim on the BMW hub, and it's probably within a pound of the KTM part. Rear axle is heavier duty on the BMW. You _might_ be able to shave some weight there, but is it worth the risk of breakage? Remember, you've got 400 pounds of bike, give or take, to support/propel/stop/etc. The rear brake caliper is literally the same, only a mirror image, between the KTM (400 EXC) and the BMW. I can swap the pads.

I would not recommend removing the cush drive from a 650 thumper, unless you're a fan of snapped chains and holed cases. Friend had that happen on a Husky TE610, with some very unhappy results.

With regards to the cush drive I agree completely. Especially for a bike that is ridden on pavement where there isn't a lot of wheel spin/slip. Having said that KTM cush drives wheels will bolt on to KTM non cush drive bikes without modification. KTM cush drives are a fair bit lighter than BMW cush drives.

With regards to the axle, the same axle supports the 950 adventure, a heavier more powerful bike. Yes it is lighter, but it is also larger in diameter (by a lot). Increases in diameter significantly increase strength compared to changes in wall thickness, plus you get a larger bearing surface.

Unsprung weight plays a much larger role in performance than sprung weight, rotational mass more again. Saving even a pound in the wheels might just translate into a significant handling difference if you're the type of rider that can push the bike to the limit.

Then there is the issue of tire selection for an 18" wheel. You have waaaay more dirt applications available, but I am not so sure about DOT applications.

Is it worth the effort and money...I doubt it.

[dwayne]

Originally Posted by Gangplank

Only weights 13 lbs total? That sounds pretty light for something that big made of steel.

Don't know what the average 600cc might weigh. Why 600cc? Why not off a 250 or 450 dirtbike? They are made to carry light dirtbikes coming down off 20 foot jumps. Do you think it will break under the load of a F650 riding dirt roads?

Keep in mind we are talking about weight savings of the swingarm + lighter wheel, rear axel, etc.

You use a thinner section when using steel, looks can be deceiving. Aluminum's strength to weight ratio is better than steel, but it strength to thickness ratio is shockingly poor compared to steel. You would also change the feel of the rear suspension, steel has more flex...I imagine there would be both good and bad things that come from a more rigid swingarm.

Again the KTM 950/990 would be a decent comparison for weight and use to a Dakar.

I suspect you wouldn't break most swingarms from modern bikes, but I can only imagine the headaches of trying to modify one (remember the bmw chain is on the "wrong" side). Take a look at which parts get modded (or not) on a tourtech rally bike as a baseline the for value of a high performance mod. I believe they use the stock swing arm.

[Gangplank]

For guys using the YZ250F or 450F front end set up and tripples with dirt bike or fat bars do you still need or want bar risers or is the stock height good enough?

[kubiak]

Originally Posted by Gangplank

For guys using the YZ250F or 450F front end set up and tripples with dirt bike or fat bars do you still need or want bar risers or is the stock height good enough?

i still run bar risers on mine. i like them high and so i can slide the yz fork tubes up in the triple clamps.

[Aquatic]

Originally Posted by LoJack

I have been learning Solid Works and have been wanting to draw it in there.

I'll save a bit of trouble if you ask nicely

Originally Posted by LoJack

A year or so ago a friend that works with SW was helping me model a swing arm that had arms fully machined out of billet that had a lattice structure for strength. It was wicked cool looking but I realized it would cost about a grand to have the arms machined. That, and the more I learned about aluminum, the less I realized I knew. That's partly what prompted me to go back to school.

You still got it lying around somewhere?

[LoJack]

I don't have the SW part file, just a .PDF. If I can get it, how about an even trade.

[WayneC1]

Ah fair trade is a wonderful thing, you want an honest broker ? my fees are reasonable

[swamp]

Originally Posted by GSBS

I used the YZ forks, wheel, brake caliper and disc, but kept the BMW master cylinder assembly on the handlebars. Trouble was there were two sizes of banjo bolt fittings for the brake line at each end.

I ordered a "universal" line which is threaded at each end and then the correct size threaded banjo bolts for caliper and master cylinder to screw onto the new line. I think it was $40-50. Has worked with no issues in nearly 12K miles.

thanks again sir