Mk Gearbox spacer dimensions

[NeilR]

Hi, can anyone please tell me the lengths of the gearbox spacers (items 11 & 12 plate 20) nos 29978 & 33763.  Thanks, Neil

[Vermont-Ian]

Mine have lengths 2..25" and 0.8" as best I can measure with a vernier caliper without taking the bike apart.
But I have to slide in a couple of washers to get a snug fit before tightening the footrests, so mine may worn be a bit short.
Measure the gap in the frame, and the width of the gearbox to get the total length
Assuming you're making them on a lathe, or cutting from tube, make them a little long to be on the safe side, then trim.
OD is not critical, of course.

Maybe you already have this info - took me a while - it's been cold out there.

Ian Stokes
Richmond, VT, USA

[eddie]

Neil,
       The Mark series machines had solid spacers which often worked loose ( there is very little 'give' in the frame due to the close proximity of a cross tube). Plus series machines and the Dragonfly had adjustable spacers in the form of a threaded sleeve and a deep nut. It may pay you to make up something similar - at least on one side. The sides of Mark gearboxes are often recessed where the spacers have been able to move.

   Regards,
                Eddie.

[NeilR]

Thanks for the help chaps.
Both of the 'boxes I have are recessed, but only on the kickstart side, I'll fit an adjustable one there.

Cheers,

Neil

[coles1933]

I have been making the 80/90 adjustable spacers for some 6 years now.The reason for these spacers on these
machines is not only to take up the space between the frame and gearbox but to also get the chain running in
a straight line between the  gearbox and rear sprocket, I can supply anybody who is interested in making these with a drawing and a data sheet showing the required set up method. The system is simple and allows a very accurate alignment to be made. Using these spacers can save you considerable power and help your fuel consumptoin figures  coles1933