Hi all, I have a 1966 A65L I had the speedo and tacko overhauled because they where in a bad state and the speedo needle very jerky. The repair chap showed me the repaired speedo working on his bench nice and smooth,when they where fitted to the bike the speedo was still a bit jerky but not as bad as before, months later I changed the cable from the gearbox this made the needle smooth but the needle didn't move until a few yards down the road and started at 10mph on rides out I thought the reading was wrong when approaching display speed cameras they displayed 30 but my speedo said 20 I rigged a satalite speedo up and that displayed 30 and my speedo 20. My speedo is SSM 5001/03A and the gearbox is I believe 2/1 and back wheel 19 inch if anyone is still awake can they confirm the gear box and speedo are compatable, thanks Roy
The A65 standard gearbox ratio is 20/16 (1.25:1) and the rear wheel is 18".
Maybe the combination of the non standard wheel size and the 2:1 gearbox is the problem.
Jerky speedo can becaused by a poorly routed or damaged cable or by a worn or otherwise damaged speedo drive gear box. The worms in the gearbox can wear quite badly.
The photos are from the Smiths list for 1966, the first showing the speedo and gearbox numbers and the second showing the gearbox ratios. The speedos are 125 mph. If yours is 150 mph it is a later type which is not calibrated for the 1966 gearbox.
The difference in ratios between a 2:2 and 21:10 gearboxe is quite small and unlikely to be the cause of the inaccurate readings.
I believe the bike was an export brought back into the UK did some export bikes have 19 inch rear wheels thanks Roy
The UK market Lightnings, Royal Stars and Thunderbolts for 1966 had 19 inch rear wheels, the Lightnings exported to Hap Alzina in Oakland, California had 18 inch rear wheels specified. The Lightnings which went to BSA Incorporated in Nutley, New Jersey had 19 inch rear wheels specified. Smiths shows the same speedo number for the Alzina bikes but with the 2:1 speedo gearbox rather than 21:10.
Is your bike definately 1966 season?
Hi JulianS The bike came back to UK then registered in 1990 with a D registration always thought it was 1966 the engine number is A65L 14631 cant read the frame number but log book says they are the same its tax and mot exempt . Roy (the log book says it was declared manufactured in 1966)
That is certainly a 1966 season engine number, quite close to the end of the 1966 bikes. The first 1967 season models left the factory in late July 1966.
I can only suggest that you check the speedo drive gearbox for wear, make sure that it engages properly with the drive flange on the wheel, that the flange is secure ( the 1966 flange had a right hand thread and they could unscrew in use, they changed it for a left thread for 1967 models), that the cable is a good quality one in good condtion and has a good smooth run to the speedo head.
Thanks for replies, JulianS will check out your suggestions I wonder if any members with 1966 A65s with 19 inch rear wheels with a speedo drive have had any problems? thanks Roy
Hi all, put the old cable back on bike and went for a run the speedo needle was jerky between 25-35 the GPS speedo reading 30 after that 40 on speedo was same as GPS 40 same again 50 60 then be came jerky again 25 -35 so I think although the new cable was made in England the inner cable may be a shade too long so when tightened up to the speedo head its putting pressure on the rotating magnet causing it to read slow I might grind a tad off or put a spacer between knurled nut and speedo head in near future, anyone know the part number for a 2/1 speedo gearbox for 1966 A65, thanks Roy
Think I have found it in JulianS's photo, Roy
Hi Roy,
I've had to 'correct' the exposed length at the speedo end on at least 2 new cables recently. If you stick a small phillips screw driver up the hole that the cable fits into and mark on it how far it goes, you may well find that the distance is shorter than the distance above the brass collar on the end of the cable. It's quite easy to move this collar more towards the end of the cable. I would suggest a couple of mm less that the hole depth to give it some clearance.
Chris
Thanks Editor, I measured against the old one and reduced it with a bench grinder didn't know the collar could be moved thought it might have been heat shrunk on thanks for the advice, Roy
Yes, all I did was loosely place the end of the cable between the jaws in a vice with the bush above and sitting on top of the jaws. A gentle tap with a light hammer and that did the trick.