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Micha
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Joined: 10/12/2007
Posts: 425

Hi friends. I would like to study a bit about the throttle that is assembled on my bike. I took it apart last night in order to oil the cables and I faced some difficulties to put it all back together, so I left it and came here to be advised. It is different (I think) from the one shown in the BMW auxiliary catalogue or maybe it's just not shown there at all? The one that I have is operating 2 cables (and not one cable that is split later) via a gear/sprocket that pulls/pushes a small link – chain, the later is operating a sliding block with 2 grooved machined in it to accept the cables (I hope I made myself clear). All is covered with a big aluminium drop-shaped cover and is hold to place with a conical Allen screw (I'm sorry I didn't take any pictures). A friend told me that BMW's supplier for the throttle grip was called Magura.
Is he right or where there more suppliers for throttle grips?
Does Magura still exist?
Is there a special method or trick to assemble it back? Anything I should pay attention to?
Do I have to disconnect the cables from the carbs?
Are there any pictures or drawing for these throttle mechanism?
According to the catalogue there should be a grease nipple fitted and mine is missing. Is it a standard one or any thing special? Can I get it at the local shop?
Thanks a lot and a nice weekend, Micha.

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

Darryl.Richman
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VBMWMO #6285
Surf City, USA (Santa Cruz, CA)
Joined: 10/27/2006
Posts: 2186
Throttle grip mechanism

The throttle you are describing is the correct one for a /2 or perhaps later /5-/7 series bike. (The /2 throttle cover has a slotted screw holding it down.)

Your plunger frame bike would instead have come with a throttle grip that has a helix machined through the inside end of the tube. This fits inside the throttle housing, which has a linear channel on the front of it. There is a separate traveller piece (gleitstein in german) that has two grooves across the top to capture each cable end and a diagonal guide on the back that will fit in the helix of the throttle tube. The traveller runs back and forth in the channel in the housing, which also has a zerk fitting to allow the mechanism to be greased.

The /2 style throttle has the advantage of having a cam action -- because the small chain winds up on a cam -- with more cable pull the further towards wide open throttle you get, for a given twist. The /3 style is linear in action.

Although Magura still exists, they do not manufacture these throttles any more. You can, however, buy a complete reproduction of either type from the usual Mobile Tradition parts sources (Vech, Mark Huggett, or order through any BMW dealer, if you can show them the correct current part number).

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saintclair2703
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VBMWMO #2703
Asheville
Joined: 10/27/2006
Posts: 89
Throttle grip mechanism

The question is how to put it back together?

The top has a piece that hangs down, which corresponds to a slot in the throttle tube. Grease that as well as the gear and chain. One cable end goes in the retainer end of the top, and the other goes in the bottom. It should drive you crazy trying to get that part co-ordinated by itself. You'll need to orchestrate pulling on the cables, locating the top tab into the throttle slot while keeping tension on the cables -and in their little retainer things-as you rotate the throttle slowly until the tab slips into the slot, and then keeping pressure while tightening the screw.
There should be almost no lag between turning the throttle and the opening of the carb slides. If you get it right the first time, you're either blindingly handsome, rich, and talented- or just really lucky.

Hope that helps.

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Micha
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Joined: 10/12/2007
Posts: 425
Throttle grip mechanism

Thanks a lot guys. Probably I was just lucky…

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

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