R51/3 Throttle Cable Conundrum

[Vegtamr]

I've run into a hiccup in replacing throttle cables on my 1951 R51/3.

As shown in the attached photos, I have a non-standard throttle control. Mike at Vintage Beemer parts seems to think that it may be an aftermarket product as it doesn't match any stock controls from the era. It's basically just a two-part housing that clamps around the bars and engages with the throttle tube directly; there is no cam or any other kind of linkage. The cables seat directly on the throttle tube.

The issue that I am having is that the stock throttle cables that I ordered (13 21 2 072 356, for sidecar bars) do not have enough exposed cable beyond the sheath to both seat at the control end and to thread through the carb top and engage with the slide. Compared to the (50+ year old) cables that came off the bike, they need about 25mm less sheath. The overall length of the old cables is 1115mm, with roughly 970mm of sheath and 145mm of exposed cable. The terminations are the same as the stock cables.

Does anyone A) have any insight into where this throttle control is from and B) have a suggestion for a cable that would fit correctly? Otherwise I may be going the route of custom.

Thanks

Joshua

[Darryl.Richman]

I think I've seen some British bikes that had throttles like that. It's definitely not a /3 throttle, which has a spiral groove that moves a traveler back and forth, and the traveler captures the cable ends. Looks like you're on your own here.

Making your own cables isn't difficult, but you need a high power soldering gun and solder, and you need the right cable ends. I've made cables for my prewar bikes, and I get the parts from Flanders Co.: http://www.flanderscables.com/

There are other places to buy as well.

[caker]

Hi. I have successfully removed a few mm of casing from an already-made cable before, being very careful with a dremel tool to cut through the plastic and flat metal wound sheathing. You just need to be super careful and not cut any of the inner cable wire strands. Maybe that's helpful for you...

-Chris

[vechorik1373]

The correct right hand throttle with the lever looks like this. Referred to as a sliding block throttle.
They are available new. 32 72 2 072 350 is the part number.
Now, if you buy one, keep in mind that there are 3 set screws ( #11) that hold it together. ONE of them has a dog point. the handlebar must have a hole drilled in it, (if yours doesn't, drill one!) for the dog point of the long set screw to go into. That is what keeps the whole assembly from twisting when you open the throttle. BE CAREFUL, if you over tighten these set screws you will shatter the housing and ruin the throttle!

[vechorik1373]

One more thing. Should you decide to make your own cables, use 95/5 solder.
60/40 is too weak.

[R68]

You have a "Magura Quick Throttle" on your motorcycle. It was used on BMW racing motorcycles, and on the Zundapp KS601...and is quite desirable. You also have Magura Enduro levers on the bike, sometimes sold as the very desirable Magura racing levers...Here's a picture of that throttle and the racing levers. If you use the Quick throttle you'll get much faster throttle response that with the stock throttle casting.

[Vegtamr]

@R68 Thanks! That clarifies a lot. This bike has been in the family since 1976 or so, and while the engine and gearbox were rebuilt 20 years ago there is a lot that was never touched while my father had custody.

Sounds like I am looking at custom cables in that case...

[wa1nca]

Great news from R68 !!!
Is your gas tank the same as his

IMG_4208_2_12.JPG (59.62 KiB) Viewed 1146 times

[niall4473]

Vech, is 95/5 solder OK to use with brass nipples?, as when I was doing gas work I was told not use it on any brass fittings.

[vechorik1373]

If you do not use 95/5 to solder the ends onto the steel cable, the ends will pull off sooner or later. That can get exciting if it is a front brake cable! Just be careful, you do not want to turn the strands of the cable red. that will de-temper the steel wire, and it will break there.