Scooterotica

I'm at the end of my tether with this one. Speedo working one minute then not working the next.
I narrowed it down to the speedo drive. I've bought and fitted a new metal wheel and worm gear. Speedo worked after a fashion for a shirt time now bugger all. The cable turns the speedo but the worm will not mesh with the wheel when it is assembled. I've tried for hours to get this to work but the only way the wheel and worm mesh is if the housing is taken off and the drive spindle is tilted towards the top of the casting. Sitting it centrally and I can feel that the worm isn't meshing with the wheel.
Any ideas anyone PLEASE

I've seen some with little plastic or brass shims in between the worm and the backplate, this will raise it a bit.

Off the MB site http://lambrettaspares.com/spares/front ... 0088s.html
"Tips
When fitting these new speedo drives sometimes they may need lapping in with grinding paste, this is because there are so many differences in machined hubs.

Occasionally the speedo drive pinion may need some modification or a washer fitting first, this again is because there are so many different hubs all been machined different. "

When I fitted mine I had to lap it with grinding paste to bed it in

DaveTomo wrote:Off the MB site http://lambrettaspares.com/spares/front ... 0088s.html
"Tips
When fitting these new speedo drives sometimes they may need lapping in with grinding paste, this is because there are so many differences in machined hubs.

Occasionally the speedo drive pinion may need some modification or a washer fitting first, this again is because there are so many different hubs all been machined different. "

When I fitted mine I had to lap it with grinding paste to bed it in

Lol never saw that foot note when i got mine but i did check the fit before build and it has been fine. Is it an mbd one the op has fitted ??

Thanks for the replies, I got mine from Sundarscooters off EBay.
I assume you mean lap the worm into the wheel with paste? Although with mine fitted I could turn the worm gear in the hub with an allen key. It didn't seem to mesh at all.
I've tried washers, differing numbers of in differing positions and still no joy. I get fed up last night after 2 hours of buggering about. I'll take note of the tips given above and have another fettle tonight.

I put a 6 mm SS washer on the worm drive before installing it into the hub so it would sit more central and another on the other end and put the rest back in. Then stick a matchstick or terminal driver up where the cable goes and make sure the drive will turn freely and smoothly with some grease on. This is before even fitting the back plate. There is a lot of slack in there, and I had to linish the second washer so it didn't bind. Then fit the back plate and do the same with the matchstick/driver. Watch the matchstick as you turn the plate and make sure it turns evenly all the way round. At first mine would turn and then just stay still and then turn again as it picked up the drive. I ended up cutting off the old drive and putting a steel one on from Sundar scoots as you have, as the old nylon one was clearly worn. Took it out yesterday and have a nice smooth speedo action, although accuracy was out of sinc with my Garmin GPS by about 10 MPH

Thanks Dapper, the funny thing is I had a steady speedo action when I 1st installed the new worm and wheel just before the weekend, albeit reading slow. Then it just stopped altogether.

Time to strip the lot down AGAIN and put all the above tips to the test.

dapper wrote:,although accuracy was out of sinc with my Garmin GPS by about 10 MPH

How do you think there are so many 90mph scooters about.

I've seen two types of worm,one has a peg the same size as the shaft the other has a larger end that fits in the backplate. So check the hole for the size of worm needed and whether the hole is worn causing the worm to disengage

After much buggering about I got mine to work perfectly - for about 3 miles now nothing, not even a flicker.
It's all down to the drive. As an engineer I find it baffling that something so simple can be so utterly unreliable.
I going to fit ANOTHER worm and wheel, plastic this time.