BMW airhead, quick fork question

DisplacedYankee · 05-17-2010, 08:22 PM

Any help or suggestions appreciated...

I have auxiliary instrument mounts on my R90/6 that are secured under the top "guide support" bolts (#8, picture A). What's the best way to remove these bolts in order to remove the mounts (the bolts are in there tight)? Also, what size wrench or socket do I need to get, these are larger than anything I have. Mounts in questions are #14 in picture B.

Picture A.

Picture B.

Bigger Al · 05-18-2010, 06:54 AM

The top clamp nuts are 36mm in diameter, and there's a wrench in the stock BMW tool kit to take them loose. It's really short, so I usually get a 1-1/4" wrench on the other end for leverage.
Use caution as when you remove the nuts, too, as they are also the fork spring keepers. It's easy to get a finger pinched between the nuts and the handlebars. DAMHIK.

DisplacedYankee · 05-18-2010, 07:16 AM

I don't have the 36 mm wrench in my kit (recently got the bike), and I think that's for the axle bolt, too. I'll pick up a wrench for the bike and socket for home use. This is all part of changing out the handlebars, so they'll be off when I remove the nut.

Thanks!

Bigger Al · 05-18-2010, 11:32 AM

Quote:

Originally Posted by DisplacedYankee

I don't have the 36 mm wrench in my kit (recently got the bike), and I think that's for the axle bolt, too. I'll pick up a wrench for the bike and socket for home use. This is all part of changing out the handlebars, so they'll be off when I remove the nut.

Thanks!

The axle nuts are 22mm, or 7/8". All three top clamp nuts are 36mm. You can still order the original tool from BMW, but my guess is that's kinda pricey.

Boon Booni · 05-19-2010, 05:04 PM

Quote:

Originally Posted by DisplacedYankee

I don't have the 36 mm wrench in my kit (recently got the bike), and I think that's for the axle bolt, too. I'll pick up a wrench for the bike and socket for home use. This is all part of changing out the handlebars, so they'll be off when I remove the nut.

Thanks!

The socket will have to be ground flat. The face of most sockets have a bevel/taper. Those bolt heads are so flat that the socket won't bite unless you grind it down. Same with most large box end wrenches. They'll have to be ground down.

I think you'll probably have to removed the handlebars to get in there with any tool.

P B G · 05-19-2010, 05:44 PM

Right, your best bet is to get the appropriate wrench, I believe its still available, otherwise I also think its the same wrench used on Porsche Fan Belt pulleys. A socket can be used if ground but it is unwieldy in that the center of torque applied is 2" above the very skinny bolt.

These top nuts do a few things as mentioned, importantly they hold in the springs, so make sure its supported off the front tire. They also locate the plate in relationship to the lower clamp.

That is if you remove the nut/bolt and reinstall you can actually change the alignment of the fork tubes and end up with a binding fork. Much has been written about this issue and the use of a "torque relief bar" basically to prevent the torque on the bolt from applying torsion and flexing the system they apply counter pressure using a pry bar.

And lastly, these suckers are supposed to be tight, iirc 90-100 ft pounds.

I have these same plates on my bike, I have an S fairing. I normally ride with out the S fairing. But I leave those plates in. Not worth the effort to remove/replace if I want to use a fairing.

DisplacedYankee · 05-19-2010, 08:09 PM

Thanks for the input. I ordered the proper wrench from Hucky's today and will look into the alignment issue before I get started. Is this going to be a deal breaker? I don't use the mounts and they annoy me just hanging out there.

P B G · 05-19-2010, 08:18 PM

Nah they aren't that bad, its just basically that you want to tighten the fork cap, but you don't want to do so against the steering stop. So you have to use a pry bar or large screwdriver to resist the tightening effort.

Should be covered in any article on fork stiction relating to airheads.

05-20-2010, 05:01 AM

I quit using the stock wrench because of the stress it puts on the corners of the nuts, being a bit of a loose fit. I now use a quality adjustable wrench, I can get a perfect fit and it has more leverage. I polished all the doodads and don't use a dash pad so I want everything to stay all purdy.

Rucksta · 05-20-2010, 05:49 AM

I have a 36mm ring spanner ground flat (no bevel) and thin on the bottom. The top side is ground to a taper towards the front. It can service the centre nut without removing or loosening the handlebars. Very handy for for doing steering head bearing adjustments as well as fork top nut removal.

Cheap as at an Auto store

05-18-2010, 06:54 AM	#2
Bigger Al Still a stupid tire guy Joined: Oct 2004 Location: Auburn, CA Oddometer: 7,339	The top clamp nuts are 36mm in diameter, and there's a wrench in the stock BMW tool kit to take them loose. It's really short, so I usually get a 1-1/4" wrench on the other end for leverage. Use caution as when you remove the nuts, too, as they are also the fork spring keepers. It's easy to get a finger pinched between the nuts and the handlebars. DAMHIK. __________________ "Nearly all men can stand adversity, but if you want to test a man's character, give him power." - Abraham Lincoln

05-18-2010, 07:16 AM	#3
DisplacedYankee ^OP Voyageur Joined: Mar 2010 Location: Virginia Oddometer: 79	I don't have the 36 mm wrench in my kit (recently got the bike), and I think that's for the axle bolt, too. I'll pick up a wrench for the bike and socket for home use. This is all part of changing out the handlebars, so they'll be off when I remove the nut. Thanks! __________________ 1976 R90/6

05-19-2010, 08:09 PM	#7
DisplacedYankee ^OP Voyageur Joined: Mar 2010 Location: Virginia Oddometer: 79	Thanks for the input. I ordered the proper wrench from Hucky's today and will look into the alignment issue before I get started. Is this going to be a deal breaker? I don't use the mounts and they annoy me just hanging out there. __________________ 1976 R90/6

05-20-2010, 05:49 AM	#10
Rucksta Chronic Noob Joined: Oct 2008 Location: Gold Coast Oddometer: 2,300	I have a 36mm ring spanner ground flat (no bevel) and thin on the bottom. The top side is ground to a taper towards the front. It can service the centre nut without removing or loosening the handlebars. Very handy for for doing steering head bearing adjustments as well as fork top nut removal. Cheap as at an Auto store __________________ If the Earth is flat why are my tyres round?

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05-17-2010, 08:22 PM	#1
DisplacedYankee ^OP Voyageur Joined: Mar 2010 Location: Virginia Oddometer: 79	BMW airhead, quick fork question Any help or suggestions appreciated... I have auxiliary instrument mounts on my R90/6 that are secured under the top "guide support" bolts (#8, picture A). What's the best way to remove these bolts in order to remove the mounts (the bolts are in there tight)? Also, what size wrench or socket do I need to get, these are larger than anything I have. Mounts in questions are #14 in picture B. Picture A. Picture B. __________________ 1976 R90/6

05-19-2010, 05:44 PM	#6
P B G Beastly Adventurer Joined: Mar 2008 Location: Greater Chicago Oddometer: 9,786	Right, your best bet is to get the appropriate wrench, I believe its still available, otherwise I also think its the same wrench used on Porsche Fan Belt pulleys. A socket can be used if ground but it is unwieldy in that the center of torque applied is 2" above the very skinny bolt. These top nuts do a few things as mentioned, importantly they hold in the springs, so make sure its supported off the front tire. They also locate the plate in relationship to the lower clamp. That is if you remove the nut/bolt and reinstall you can actually change the alignment of the fork tubes and end up with a binding fork. Much has been written about this issue and the use of a "torque relief bar" basically to prevent the torque on the bolt from applying torsion and flexing the system they apply counter pressure using a pry bar. And lastly, these suckers are supposed to be tight, iirc 90-100 ft pounds. I have these same plates on my bike, I have an S fairing. I normally ride with out the S fairing. But I leave those plates in. Not worth the effort to remove/replace if I want to use a fairing.

05-19-2010, 08:18 PM	#8
P B G Beastly Adventurer Joined: Mar 2008 Location: Greater Chicago Oddometer: 9,786	Nah they aren't that bad, its just basically that you want to tighten the fork cap, but you don't want to do so against the steering stop. So you have to use a pry bar or large screwdriver to resist the tightening effort. Should be covered in any article on fork stiction relating to airheads.

05-20-2010, 05:01 AM	#9
Jasper ST4 Guest Oddometer: n/a	I quit using the stock wrench because of the stress it puts on the corners of the nuts, being a bit of a loose fit. I now use a quality adjustable wrench, I can get a perfect fit and it has more leverage. I polished all the doodads and don't use a dash pad so I want everything to stay all purdy.