Smiths Speedometer.

Adrian Pancaldi · Post by **Adrian Pancaldi** » Fri Jul 04, 2003 2:02 am

Hi Alan, firstly check that the cable is the correct fit in the back of the speedo, it sounds like the cable could be too small in diameter , chronometrics don't always return back to zero. Failing this www.speedorepairs.co.uk Ph 01252 835353 I am sure the natives can recommend others. Regards Adrian

Jackson · Post by **Jackson** » Fri Jul 04, 2003 11:37 pm

I had a similar problem. If I spun the drive round with a matchstick the speedo flicked (apparently OK), but would not work when connected up.
Having checked the obvious (ie cable being driven etc) I finally discovered that the square hole in the speedo drive was totally full of dirt and grease so the drive was incomplete.
A quick clean out later and all was well.
Worth checking the cable engagement before sending the unit off.

silverarrow · Post by **silverarrow** » Mon Jul 07, 2003 12:40 pm

So often a speedo not working is a fault with the cable or drive gearbox. To prove the speedo head connect up to a battery power drill and see if all the functions are OK. A short piece of old cable is useful for this.(My drill does 32MPH!) Check II is to hold the end of the cable that fits into the speedo and get someone to turn the rear wheel. You can then feel if there is any slippage at the drive end. CheckIII Is the drive end of the cable in good nick? They do get rounded with age as can the speedo head. Les Smith

Charles. · Post by **Charles.** » Tue Jul 15, 2003 12:22 pm

Clive Turner of the Surrey Section repairs and reconditions Chronometrics as a favour for friends, you could try an email to clive.turner@aladdinscave.net and see what he says.

clive · Post by **clive** » Wed Jul 16, 2003 7:24 pm

Thanks Mark I have not advertised the repairs for many years intentionally, becasue I have not got the time to do them. As I am currently off work with complications from broken leg I may be able to help Alan though. However I have found that the problems are often the drive not the head. I attach details from the guarantee letter I send with speedos on how to check things before thinking the speedo has gone wrong.

To check the rearwheel drive box. Disconnect the cable from the speedo. Put the bike on the stand and rotate the rearwheel slowly. Grip the squared part of the cable with finger and thumb, it should not be possible to stop it turning. The usual symptom of a drivebox failure is both needle and numbers stopping at the same time, although this can also be caused by a cable broken halfway down so check this too. If you are rebuilding a bike or have just purchased a drivebox check that the cable is turning the correct way. With the rearwheel turning as though the bike was going forward the cable should be turning clockwise when viewed from above. Please note however that a few British bikes fitted anti-clockwise speedos and there are some anti-clockwise drives around. If you have the wrong match it appears that the bottom trip mileometer works but the speed and main one do not. It is also important that you have the correct ratio drivebox for your bike (all AMC machines were fitted with a 2:1 clockwise drive I think).

To check the cable. Check the last 1/4 of an inch of the cable at the head end. If it is worn this will be slightly rounded. Usual symptom of failure is a steady speed reading until about 40 mph at which point the needle will begin to swing wildly across the scale. This fault is usually caused by a pattern cable that has the wrong length of screw fitment for the head. Both Johnson's Cables and the AJS and Matchless Owners Club Spares Scheme supply the correct sort provided that you specify that it is for a Smiths Chronometric speedo and the year and bike. When screwing up the cable it is important that the inner cable is slotted into the drive and that the outer cable is held firmly in place without any movement. This is particularly important if you speedo is the sort with a very short thread.

N.B. Cable lubrication. DO NOT use oil to lubricate the inner cable. Pull it out and then use a pinch of grease between finger and thumb as you push it back in. DO NOT grease the last 18 inches of the cable. Failure to observe these rules will result in grease or oil being forced up the cable by Archimedes screw action which rapidly causes the slipping clutch to slip at the wrong moment and hence no speed reading.

To check the speedo. Insert a spade end electrical screwdriver into the drive. Looking from below flick the screwdriver anti-clockwise as fast as you can. The needle should move up to around 20 mph (more with practice) and stay there most times. If you then rotate it slowly (still anti-clockwise) it should fall back to zero (well 5 mph actually). If it does this the speed is probably working OK. Note that if you use a drill with a cable attached to drive the speedo it will not work with the usual rotation. You must have one with a reversing facility to get the correct drive. It is rare for both mileage and speed to fail at the same time so please check the drivebox and cable first. Faults which usually mean an overhaul is necessary include a wildly fluctuating reading throughout the range, winding up to 120 mph and staying there, or returning to zero erratically. The mileometer readings are particularly susceptible to vibration which can stop them turning over or even to turn backwards. Headlight mounted speedos should have a rubber grommet fitted (available from the spares scheme) and it is a good idea to put a rubber washer under the fork mounted ones.

mescal · Post by **mescal** » Tue Aug 12, 2003 12:13 pm

I thought I had already posted a reply to this with my final outcome. Checking now (since the change in format) I can not see it.

Anyway, turned out to be just the cable in the end. What had diverted me from this simple solution is that I could not turn the cable when connected to a stationary back wheel. However on further playing on the suggested advice I found that if the cable is pushed in the drive gear the right amount then when the wheel was turned the cable did not turn. I think I had been pushing the inner cable into the drive gear to far.

Thanks to all for the tips and offers of help. There is usefull info here for future reference also (ref new clocks and reconditioning etc)

Timothy Branch. · Post by **Timothy Branch.** » Tue Sep 16, 2003 10:05 am

I did read somewhere that teh Smith Speedo's only return to 0 when the cable is rotated slowly. Don't know why , but worth running it on a hand drill and turning it backwards slowly and seeing if this resets the dial..

silverarrow · Post by **silverarrow** » Tue Sep 16, 2003 1:07 pm

It's so you can see how fast you were going when you hit a brick wall.

Les Smith (silverarrow397)