Clutch drag/gearbox

Previously jonathan_hall wrote:

Hi to everyone.I put a question on here in December 2012 about clutch drag, having carried out all suggestions i still have the same problem. I've now gone down a more technical route and require some info please.I have a 1952 ES2 with a laydown gearbox and I am considered about the trueness of the main shaft also the clutch hub which seams to swash as I rotate the main shaft .does anyone know the factory tolerances please .All the best, John.

john.

i also had the same problem with my es2 tried all usual stuff still would drag [some days worse than others]so i put up with it for a few years.it would slip if i over rev it..but for a 1940s single was i expecting too much ?/// then two years ago i fitted a bob newby belt drive.i often do 150 plus miles on a sunday with my mate who has a model 19 with a norvil belt drive and he has no trouble to...i,ve not even adjusted it in 2yrs.also runs oil free.i do have a small oil leak from the gearbox shaft ..there was another tread recently about tying to seal the primery chaincase[i have no problem there to]. there will be people reading this saying its not worth the expense.but for me so far its trouble free.if you only do a few miles here and there put up with what you,ve got////.riding our singles means more to us than the price of a belt drive.....good luck tony

Jonathan

I am the bloke who Tony refers to above with the model 19 rigid. As Tony says, since putting the Newby belt drive on his bike it has been faultless.

The previous owner of my bike had fitted a Hemmings belt drive with a commando clutch. This clutch did drag and getting it into neutral was difficult, so I replaced the thrust washer and shimmed the lay shaft to get rid of almost all the end float. This made it a lot better, but still not perfect.

Tonys bike has a dolls head gearbox fitted whereas you and I have lay down gearboxes, but both have the same clutch lifting mechanism, ie a worm.

So I then looked at the clutch lifting. Check that your bike has the right centres between the the lever pivot and the nipple - the distance you need is on a previous thread on the singles section but I can't find it right now.

Also my bike was fitted with the twist grip rubbers as fitted to Commandos.These are quiet fat and prevent the lever pulling back enough to the bars. Tony gave me a pair of Dowety rubbers which allowed my levers to come back another 1/8 of an inch. With those fitted my clutch is almost, but not quiet, perfect.

People on this forum have said that belt drives on singles is an over the top solution, but they are super light to pull in, never slip, and the chain case oil leak problem is removed. You v just got make sure you get that last fraction of an inch of clutch lift to get rid of any drag.

As Pete says, the Norton worm does need substantial movement at the lever. It should be 1 1/8" between centres (pivot to cable fixing) - Most (all) pattern levers aren't. In theory, this gives a heavier clutch but these are very light clutches anyway. The AMC box has a lifting mechanism which requires far less movement and if a Commando clutch is fitted to a laydown box, it may be necessary to hide an extra pivot under the fuel tank to increase the movement. I've seen this done on an early Dommie.

I've been out on my Dollshead 16H today and the clutch is great. I can paddle it backwards in gear with the lever pulled in which is an effective test in the real world.