i have searched for previous "speedo" stuff but ....

Speedo went to sleep after bike had been sitting for a week.
It did this about six months ago but a couple of hundred kms down the road, it just restarted.
When it didn't this time, i wiped the transducer thingy in the Final drive and it started operating again.
All fine until i had to stop at some roadworks and then the needle just lay down.

What is going on? is the problem at the front or the rear.

had the same issue for a while now...tried the soldering iron at the sensor trick - nothing...cleaned up a whole load of connectors under tank & connectors in speedo housing itself - nada!
Am thinking its sensor itself...just wanna check on here that the speedo does work when bikes on centre stand & running in 1st gear...

if you did a bit of searching dave  you find many posts

heres what I think at least

the sensor in the rear does pickup metallic stuff wearing off  the gear sets ...

did you think to drain the fluid bearing the small particles ...or just leave them in there to circulate again and again

next is the mid harness connector (just under the right hand sidecover )  a 2 pin device from the sensor to the harness cables ....these are known to become dry joint after some time ....get some deoxit and clean this connection ...it may take a little working the contacts a little to free up the corrosion that builds up there

after that is the instruments cluster connections ...they have to be found sometimes provide issues ...( from my way of thinking  electrolysis of the nickel plated pins and the socket connection ) that is a little trickier ...but again deoxit could help

internal corrosion issues also have been noted on the various circuit boards and connects to and from   for us out here with generally dry conditions more a rarity but it can happen

its all about service on those prone areas ...our bikes are not new and many have been left unconcidered for a long time  ...do the things that should have been done years ago and hope that the corrosion hasn't gone too far  without any attention .

if you ask me, if any automotive connector exposed to the elements can last 29 years ...that is a big plus ...many will never see half that life reliably

good luck mate ..it isn't hard ....but needs to be done by someone ...

Markzz wrote:had the same issue for a while now...tried the soldering iron at the sensor trick - nothing...cleaned up a whole load of connectors under tank & connectors in speedo housing itself - nada!
Am thinking its sensor itself...just wanna check on here that the speedo does work when bikes on centre stand & running in 1st gear...

get the karumba software mark ...and inject audio pulses from your laptop into the right hand side  sensor connection .... this will test the accuracy of the instruments ....and give you a trail of connections to test before it gets to the speedo physically

cheers

Also check the three pin connector behind the speedo (inside the cluster)
............a known problem source.

charlie99 wrote:


get the karumba software mark ...and inject audio pulses from your laptop into the right hand side  sensor connection .... this will test the accuracy of the instruments ....and give you a trail of connections to test before it gets to the speedo physically

cheers

 I've seen the Karumba thread but put my head back under the blankets after reading a bit. (invoking the 2 golden rules (1) if you don't know anything about it then.........    
                  (2) if it aint broke........

So given that I am still booked into a tutorial on K electronics, 'injecting audio pulses fr my laptop' might not be a good idea at this stage.
I will however change the FD oil and flush it out (seems most likely to be the culprit) and clean the other terminals. Won't be touching the speedo unit though unless supervised.

This one interests me too.

My RT speedo and odometer does not work but everything else does. Rev counter is used to calculate speed.

Cleaned sensor at final drive, checked connection at side cover. Not tested it but physical condition looks ok. My suspicion is the rear sensor. Now I am thinking to swap it with the one in the LT, same FD ratio.

There are times I think to swap the whole head unit but the LT is 92 and the RT 84 and they are not interchangeable.

Just to add some info to try and solve the problem. Some of us in hot climates have instrument problems that may not exist in other places. One of my bikes could get to 2200 revs on the tacho....whether the engine was off or when I was doing 4000. The odo face in the instrument panel had warped and the needle jammed. On the other bike I had the speedo working, not working etc.. It turned out that the speedo face was warped and the round hole around the speedo needle had moved, therefore catching the needle. Early Toyotas in Australia were known for the speedo needle droop where the needle resembled something that none of us want to see.

Have just replaced the cluster with one fr the RT I wrecked out and have now got a good clock display and all the lights (red brake test etc) 
BUT
the speedo doesn't work despite my cleaning the transducer again.  

Next steps
new oil in FD
check all the stuff up above in posts.
Get cluster off RS #2 and fit.

I didn't have a working speedo to check against RPM which was the second objective of swap.

Old tacho was showing 4400 at 100kph. Hope that this one is 3800 RPM at 100.- but it didn't feel like it on the way home. Will get the GPS hooked up.

Mine does 4000 at 100km p h.. you could do what I do...get a pushbike speedo/computer and run it off your front wheel...digital speed, average speed,highest speed, time taken etc. Etc.cheap at about$ 28.

an rs diff would make that tacho rev and speed about right at 3800revs and 100 kph

just as an addition ....the term "us" .....usually means that the item cannot be serviced by the local maintenance staff...actually trained in such things  ...usually under a warranty agreement and lack of training preparations by the purchaser - organisation other than to say that they don't have the any further testing that they are prepared or capable to do .

it irks me no end

what It does need, is a service by someone that knows what to do ...I would be far happier to see "needs service, do not depend on accuracy "

some times I wonder if the folks that use that terminology are capable or even conversant with the technology involved for making the call of  "us " ....   "help required " is far more acceptable to me .

sorry rant over

Yes, been out to test the cluster fr No 3 that i put into my reg No 1 RS and now get 100 kph - 4000 rpm (used to be 4400).
What is irritating, is that when you go to a roadtest report for the RS  to get the road speed at 1000rpm, like the TWO WHEELS april 1984 issue. It says that the tester was doing 168kph at 6000rpm - i.e 28kph per 1000rpm not 25 as guys are reporting here. Mike Woollet in "Classic Motorcycle" said he was doing 100mph i e. 162 kph at 5000rpm - clearly wrong.

With a lot of the TW older road tests they used to have a specs table at the end of the test and give the 1000rpm speed but this 1984 test hasn't got it. 
Anybody got another test giving this figure.

I'm about to get the cluster off No 2 and try that for a speedo. If that's dodgy then I'll have to do the unpalatable and start checking connections.

We have these speed sensing road signs that display your speed. On the RT/LT that gives me exactly 100kph at 4,000rpm on a 130/90 rear tyre.

I do have a spare RS final drive which will go on the RT at some point but the difference should only be about 3% and hardly noticeable.

I did work it out once and the difference between 2.91 and 2.81 drive was 80rpm at 100kph. I have a 2.62 ratio drive in my K1100 and that makes for 3750rpm at 100kph.

You're coming it from the angle of not being sure of what the road speed is. That is easy to determine correctly - either the road board thingy that you mentioned or I can do GPS.
What is questionable is the tacho reading that corelates to this speed. My first read 4400 - now shown to be at least 400 out. The second seems to be Ok but not the 3800 one tester reported 100kph as being.
I'm a bit puzzled as to why these tachos are so variable, seemingly from new. Even with these old ones it's not a case of the tachos being lazy, they just seem to be ones that aren't accurate. These didn't come fr the MZ factory at Zchopau on the other side!!!.

Yes am aware that a 140/80 gives a difference of 70/80rpm  fr the original 130/90, now unprocurable, but having a larger circumference)

I await the results of my next cluster transplant with interest.

can you clarify, rick. In first sentence are you talking about the diff between 100 RT and !00 RS

Dave, I put this Excel speed calculator together just for this sort of thing.

Engine Speed to Road Speed Calculator.xlsx

It seems to be accurate but don't forget that many things can change tyre circumfrence and hence the final speed calculation.
For ease and accuracy I've used the measurement from the ground to the bottom of the rear wheel hub cover to determine radius and then circumference. Best to do this off the stand with someone sitting on it of course.

The link takes you to the doc on the Bicasa site. Then click the download button at top/right.

werewasi wrote:can you clarify, rick. In first sentence are you talking about the diff between 100 RT and !00 RS

Yes, I was making the point that there is not the big difference that some are saying and if the difference is there then it is the instruments that are giving bad readings.

the speedo does have a calibration potentiometer ...which depending on instrument clusters ...and previous adjustments by owners according to tyre sizes preferred , could be out ....to some degree

 I have always thought that the early tacho gauge (83-85 ) was  always a little erm  wayward or over enthusiastic ...I predict that the electronic components in that gauge could have been better chosen for stability and compliance ...it would not be hard to replace the electrolytic capacitors with 28 year old younger ones ...that may be more in spec  and present a closer to actual correct reading .

 I just want some one to prove it ,,,equipped with the early version of instruments and practical knowledge of electronics ...or perhaps send one to me for evaluation ...( for return afterwards of corse )

might solve a few answers of calibration inconsistencies across the many models and years of production .

Charlie, would you like my 83 basic set of instruments to play with? At the moment the odo cogs are out, being used until new ones arrive. The tacho side works but speedo/odo/trip doesnt. I think a wire or clear tape thing may not be letting the power through. I should have everything back together in about a week or so.

sounds good guys

I recon I can pulse the tacho with pulses  equivalent to revs and just see how accurate that is with the equipment I use everyday ( a good Techtronic's cro _ and a frequency generator of reasonable to high accuracy )

my proposition is to measure the  readings  at about half scale  ( 4000 - 5000 revs )  and see what it reads ...without adjustment ,
then if possible ....look up the differences between the circuits on the different versions .

perhaps, if someone has the older circuit diagrams ( I guess hard to find, as most superceeded diagrams get deleted in preference for the replacement and or current versions )
perhaps the circuit board carries a release date - version number  like many of the stuff that we manufacture .

then, when the homework is done  and depending on findings ,,, components could be changed  to reflect  if possible the updates ..if not available ..just new same for same components . and redo the same tests , noting outcomes - changes.


I would appreciate any other diagrams that come from our brother forums that folks that can recover from the net  and are relevant   (possibly some language translation might be needed  inge ... and many of our European friends could help ? ) this is a wonderful place isn't it ?

how does that sound ?

cheers