Speedometer Not Correct - HELP!

[schrader7032]

Mike -

Can you post what the final drive ratio is for the bike? It's stamped near the fill plug on the driveshaft. Probably something like 25/8. Also, what is the small number on the face of the speedometer? Assuming it's in MPH, it should be something like 1.2. I suspect you don't have the right ratio on the speedometer to match the final drive.

[Lincoln]

Or there could be a problem with the speedo itself, causing the gearing inside to bind. Mine on my 69S was reading way higher than it should have. It needed an overhaul, which I had done by Terry Vrla in Oregon. Continuing to keep the speedo cable connected could cause major, very expensive damage, if the problem is in the speedo. You can disconnect it easily enough, by removing the headlight from the headlight housing and unscrewing the knurled connection at the bottom of the speedo. I recommend Terry very highly. He's repaired two speedos for me, at a very reasonable price. Only downside is that he's so busy he's got a four-month turnaround.

[Bruce Frey]

Check your odometer to see if it is measuring distance correctly. The odometer is directly connected to the drive train. This will tell you if your speedometer has the right "w" (the small number Kurt mentioned which is sort of the speedometer's internal gearing) to correspond to your rear drive.

The speed function IS NOT directly connected and can be adjusted independently.

Bruce

[Darryl.Richman]

Hi Guys, I am a new member and have read through much of what's been posted here and am assured you-all might be able to help. I have a 1965 R50/2 (Dover White) that runs fairly well. I rode her for several hours yesterday and had fun. But, as I've ridden with friends, with newer bikes, I've been told the speed indicated on my speedometer is way off. The speedo actually indicated I'm going much slower than I really am (according to their speedos).

Whats wrong with my speedometer and how might I fix it?

Thanks in advance for your advice! I'll be looking back later today to see if anyone offers any advice...

Kennedy, Mike

[Bruce Frey]

Here are the "w" factors for some of the rear drive ratios you might have (for speedo indication in miles-for metric divide by 1.6):
25/8 = 1.2
26/6 = 1.6
27/7 = 1.44

Speedo face plates can be changed, so what it says may or may not be what you actually have after all these years, which is why I suggested checking the odometer calibration.

Bruce

[Kennedy Mike]

Thanks Guys for responding!
The final drive shows a number of 25/8 and the speedo says 1.2.

When I'm riding the bike the speedo seems to be working without binding up and doesn't make any noises. The needle seems to move freely and doesn't seem to complain. It just registers a speed that's too slow. The milage and trip numbers seem to move as needed (I'm not sure if they are registering milage correctly), but for now I'm more interested in getting the "speed indicated" to be closer to correct.

How do I contact Terry Vrla?

Bruce, you mentioned the speed function can be adjusted...?

Mike

[schrader7032]

Mike -

Sounds like you do have some internal problems...most likely there's extra drag on the mechanism so it's registering slow. Could be rust, dirt, etc. Terry doesn't have a website but can be reached by email at:

terryvrla at hotmail dot com (in Hillsboro, OR)

Typically the way the speedometer works is that the spinning cable end "influences" the speedometer needle...this is done with a rotating piece of metal in the vicinity of a magnet. The air gap between the steel and magnet defines how much the needle is influenced. Here's a website that discusses this for a later model BMW. I suspect the approach would be similar for a /2, but I'm sure there are many differences.

http://home.jtan.com/~joe/speedo.htm

It would be pretty easy to make matters worse if you didn't know what you were doing. Best to get someone experienced with this work.

[Bruce Frey]

The link to Joe Dille's article that Kurt posted is the same one I was thinking of.

I have had good luck with Overseas Speedometer in Austin, TX. http://www.speedometer.com/

Bruce

[malmac]

While this is less likely to be a problem, it is still a factor to consider.

The other thing to consider which will be confirmed using the mileage test - is that the case might say 25/8 but the final drive may have been rebuilt with different gearing - something else to consider.


Mal

[Kennedy Mike]

OK, thank you all for your wisdom. It looks like I have some work to do; like a "milage test", to start with.

I live here in Cincinnati, Ohio and it's not a small city. By that I mean the folks who do drive up and down the highway do not suffer older motorcycles going slower then them very well. I will venture out on the only roads, around here, with signed milage markers, to do that test, but maybe on an early Sunday morning...

Thanks also for the resources named to repair the speedometer. I would have not known where to look without your help.

I'll try to remember to let you know what happens.

Mike