R51/3 - 1952: Which speedometer should I order?

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Micha
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R51/3 - 1952: Which speedometer should I order?

Post by Micha »

Given that I do not have a speedometer at all, or lets say it is a totall wreck and useless, how do I know what to order?
How do I know what fits my motorcycle?
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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schrader7032
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Re: R51/3 - 1952: Which speedometer should I order?

Post by schrader7032 »

Here's a list of speedometer ratios that go with various models and final drives:

http://bmwvmca.org/joomla/index.php?opt ... &Itemid=37
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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Micha
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Location: Israel

Re: R51/3 - 1952: Which speedometer should I order?

Post by Micha »

Evening Kurt, Thank you.
Does it means I need to know the final drive ratio on my bike?
I think that my 51/3 went through a change on that as I discovered when rebuilding my final drive and asking here some question. Is it the number that is stamped on the main big gear?
If so - then I'm in trouble.
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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wa1nca
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Location: Ashfield Ma

Re: R51/3 - 1952: Which speedometer should I order?

Post by wa1nca »

The solo rear end ratio for r51/3 should be 39.9 and speedo for km should be w.95 and mph 1.52 according to the chart Kurt posted
But if final drive gears were changed to a different ratio one should have updated the number on the final drive
if not the drive would have to come apart and teeth counted to find out the gear ratio
Kurt thanks for that chart
Tommy
Tommy Byrnes
54 R51/3 55 R50/Velorex 560 sidecar 64 R27 68 R69US
Ashfield, Ma
USA

olebmw
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Re: R51/3 - 1952: Which speedometer should I order?

Post by olebmw »

You may be able to count the ring gear teeth by looking into one of the oil plug holes.

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schrader7032
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Re: R51/3 - 1952: Which speedometer should I order?

Post by schrader7032 »

Try counting the number of turns of the transmission output (in neutral) for exactly one turn of the rear wheel. Put a chalk mark on the rubber and turn push the bike while in gear. Probably this could also be done with the bike on center stand. Not an exact science, but you should be able to get close enough to identify one of the limited number of ratios.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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Micha
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Re: R51/3 - 1952: Which speedometer should I order?

Post by Micha »

wa1nca wrote:
Thu Nov 19, 2020 1:59 pm
The solo rear end ratio for r51/3 should be 39.9 and speedo for km should be w.95 and mph 1.52 according to the chart Kurt posted
Hi Tommy,
Shouldn't it be 35:9 for a solo bike?
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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Micha
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Location: Israel

Re: R51/3 - 1952: Which speedometer should I order?

Post by Micha »

Found stamping on the device, made by SWF.
Can someone pls explain what they mean?
I'm quiet sure my bike went through some strange changes during its time here in IL.
Already found that the stamping on the main rear gear is 35x8, hence for a R67 serie with s/c...
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Michael Steinmann
R51/3 1952
Engine Nr. 529466

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Micha
Posts: 440
Joined: Fri Oct 12, 2007 2:24 am
Location: Israel

Re: R51/3 - 1952: Which speedometer should I order?

Post by Micha »

Another thing:
Since I'm not in a hurry, and I have tools and time, I'll try to disassemble the speedometer and see what the problem is with it (I remember it was moving but frantically, so maybe it's fine and all the problem was with the speedo cable, which is new now). Does anyone have any idea how to approach the work of dismantling? I could not find anything on the Internet that could help me.
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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Micha
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Joined: Fri Oct 12, 2007 2:24 am
Location: Israel

Re: R51/3 - 1952: Which speedometer should I order?

Post by Micha »

Well I disassembled the device. The internal assembly looks ok, more or less.
The strange thing is that when I turn the spindle, the dial only moves when the device is upside down, or tilted to the side. When the dial face is towards me, the rotation of the spindle does not move the dial at all.
Any idea why? Doesn't it like me?
What does W-980 means?

Is it possible to dip the mechanism in some kind of solvent, dry it and lube? Will kerosin, terpentine or alike harm the internals? Not interested in breaking it down beyond that.
What oil shell I use afterwards for lube?
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Michael Steinmann
R51/3 1952
Engine Nr. 529466

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