I have recently bought a semi finished trike based on the K100RS and I am finishing it off now, and it is on the road, btu not quite completed, and among those little issues, is the speedo. Weirdly, I am sure that it did work and now it does not, but I have tried to trace things back, but can I find anything??? I have the manual and I find out the Speedo is done by a magnet in the back end rather than a cable in the front, and this is a new thing for me, but hey ho.

So anyway, weirdly, I have thrown a Pushbike speedo on and I think its roughly calibrated about right... Enough for keeping me within the speed limits at least, but I want the proper thing to work.

What options do I have for this?

Its a 1983 K100RS - the early fuel injected version ( it has a choke FFS ).

Thanks guys.

Might be the magnetic reed switch that senses the magnet on the wheel that has failed. Test it with an ohmmeter.

Sorry, but I cannot find anything that suggests that there was even one there to start with?

I think its more likely, that I will have to start one off from scratch perhaps, using the Actual speedo from the BMW, but instead of the bits being inside the BMW Rear wheel, but instead, its on one of the wheels of the trike?

I dont know where to start to be honest... I assume that it would be as simple as the magnet / sensor that you get on a pushbike is, as long as I get the right 2 wires from the clocks.??

So what's the configuration of the bike - tadpole (two wheels in the front) or delta (two wheels back)?  In other words, is the original rear drive still intact or has it been replaced?

It is hard to say what's going wrong if there are no pictures to indicate how the speedo is configured.  It's total guess work.  Can you post some pictures or write a description of how the current non-working speed is configured?

The speedo cable has a connector on the right just under the rear of the tank. This would be a good place to start. The connection can get corroded.

The trike is the front of a BMW K100 with 2 wheels at the back and a Reliant rear end. Reliant brand was I think just post war or maybe 60s and was 3 wheels 1 at the front 2 at the rear. I think that is right.

The original BMW drive had a magnetic pickup which is fixed to the rear drive just above the filler plug. I think   that drive wont be there but will have been replaced by the reliant 2 wheel setup and connected to the BMW gearbox by a custom drive shaft.   I would say that the original speedo would not have worked but if it did it would have needed some sort of device to replace the magnetic pickup that was in the rear drive.
If you want the speedo to work then of course you will need to find the magnetic pickup or make one.
The most likely place for a pickup to be placed would be by placing 2 or 3 magnets evenly spaced around the drive shaft with a sensor to give the signals.
To be quite honest I would say that to get the OEM speedo working would be a drawn out waste of time and hat you would be far better off to get an electronic aftermarket unit like one of these http://www.ebay.com.au/sch/i.html?_from=R40&_trksid=p3984.m570.l1311.R4.TR5.TRC2.A0.H1.Xmotorcycle+speedo.TRS0&_nkw=motorcycle+speedo&_sacat=0
You will find that there are other issues with the neutral light and gear position but Robmac and Charlie99 have solved these for me and others.

robmack wrote:So what's the configuration of the bike - tadpole (two wheels in the front) or delta (two wheels back)?  In other words, is the original rear drive still intact or has it been replaced?

It is hard to say what's going wrong if there are no pictures to indicate how the speedo is configured.  It's total guess work.  Can you post some pictures or write a description of how the current non-working speed is configured?

TadPole? LOL Not heard that one before... I suppose thats the CanAm Spyder then?

Ok, so sure, mine is a front end bike and back end Reliant Regal... 1 in front 2 in rear.

The original drive is all gone, and yes, it is entirely guess work for me... Worse still, is that I have to have a trike because I am disabled, have crappy legs, and only have the use of one hand, so searching for bits that dont seem to be there, kind of makes things difficult.

I will try to get to it all soon, and I will definitely provide pictures as and when I can.

Holister wrote:The speedo cable has a connector on the right just under the rear of the tank. This would be a good place to start. The connection can get corroded.

Ok that is certainly a place to start yes.
Thank you.

RicK G wrote:The trike is the front of a BMW K100 with 2 wheels at the back and a Reliant rear end. Reliant brand was I think just post war or maybe 60s and was 3 wheels 1 at the front 2 at the rear. I think that is right.

You will find that there are other issues with the neutral light and gear position but Robmac and Charlie99 have solved these for me and others.

Yes, thats the one.

And I have no issues with Neutral and gear positions myself, although I have a bit of a leak in the gearbox/shaft drive that needs sorting out... Its very slow for now, but I do have to keep an eye on the level.

Im going to have to sort that out too and thats a pain in the behind.

You will find that there are other issues with the neutral light and gear position but Robmac and Charlie99 have solved these for me and others.

This was refering to when an aftermarket speedo is used like the ones I linked to.

RicK G wrote:This was refering to when an aftermarket speedo is used like the ones I linked to.

Yes, of course. I see it now.