Gearing For A James Or Any Villiers Engined Bike

[old trials fanatic]

Looking for a few suggestions re the gearing for the James project. It's still in bits just bigger bits

So as i havent run it yet i will be having to get some sprockets ordered from Talon. If you run a Greeves or James, Sprite etc what gearing do you use?

I am using a std crank sprocket as the smaller ones need to have the crankcases modifying to get it to fit so really down to the gearbox and rear sprocket.

I know it will need fine tuning and possible adjusting once i get it up and running, the B40 was the same just fitted a smaller rear sprocket to that as it was too low geared, just like to get it nearish as i cant aford to "waste" a rear sprocket by getting one thats miles out.

Thanks in anticipation

[trialsrfun]

Lots of choices for the gearing Otf I agree with retaining the std crank sprocket, a 17t is available but needs a split link and half link in the std chain, milling off the gearbox face enables a 16t crank sprocket to be fitted again with the std primary chain but without the half link, in my experience the standard primary chains stretch and wear very quickly and are a bit suspect when worn or running slack.

With the std 20t crank sprocket fitted a heavier duty primary chain is available from Nametab this does not stretch in trials use and in my opinion is a must fit item.

Assuming you have a trials box to start with fit a 13t rear sprocket (428 rear chain size) with a 62t rear wheel sprocket.

Two lower seconds are available from Nametab a one cog (a special way of cutting the gear) or better still the two gear pair, this will mean removing a very small amount of alloy from inside the gear case but this will not harm anything Simon at Nametab will explain.

A lower third is also available but then you can have a big jump up to 4th and the std third is great for between section going.

Have you a good ignition fitted because the Villiers can be a right pain if the spark is iffy ?

Which type of James frame have you got and is it going together ok ?

Hope some of this helps good luck with the build.

[old trials fanatic]

Thanks for the info. I have fitted simons 2nd gear mod, the two cog one, and have so far left the std trials 3rd gear as i had also heard about the big jump to 4th if you fit the low 3rd gear. will see once i get her up and running if the low 3rd is required.

Havent sorted the ignition out yet. Will either be using Simons or the one that Villiers Services are selling. Need to find somebody with experience of both before i make my mind up.

The frame i have is one that Race Engineering have had made. It's going together alright. Just fitting the swing arm and headstock bearings at the moment and there is a small amount of distortion of the bearing mountings due to the welding but nothing that a dremmel and some fine emery cant sort out. Otherwise fine.

Will take a while to get it together as there is alway a lot involved in making and fitting brackets, mudguards, air filter etc etc but hope to have it something like by May 2007.

Got to get the wheels built next then i can make some more progress.

Thanks again.

[trialsrfun]

I have a Motoplat unit fitted to my bike and it is good, I have no personal experience of either of the two systems you mention but I think the one Simon sells uses the Villiers flywheel which is good because the ring weight fitted to the trials flywheel really strengthens up the bottom end power, maybe worth asking about the magnetism in the old flywheel though.

Race Engineering may also be making an ignition system based on the PVL unit as fitted to BSA/Triumph etc.

I did try the lower third and did not like the jump from 3 to 4 but in the Villiers box there are two trials thirds, 32a & 37a the lower 37a one is fitted to mine both of these are much higher than the Nametab option but I do not think it really matters which you have so try what is in there now.

Which cylinder and carb are you going to fit ?

[old trials fanatic]

I've got a Greeves square barrel but i dont know it's history so might even be a scrambles one, hope not, will have to see how it goes when i get it running.

Intend fitting an Amal Mk1 concentric.

Will have a nose around some of the bikes at the trial on Sunday and pick up a few ideas.

[bigwig]

From my limited experience you will need a bottom gear raio of 36 or 37 :1. To achieve this with 32 or 37a gearbox and a 20 tooth engine sprocket you will need 12 tooth gear box and 56 or 57 tooth rear sprockets. I have made up a scribbled chart showing many permutations of villiers gearings so you can get what you want. You can give me a ring and I'll send you a photo copy 01296712510

[totalshell]

dont go smaller than the 20t engine sproket a.. anything less and its so low it spins up very easily b.. getting the primary chain right is a real pain new chains are too tight and the advice would be to use a 'worn' chain but then they wear very quickly

so stay with the 20t sproket on the 32a i had the 13/62 combination metioned earlier

with regard to head/barrel the alloy stuff certainly are the 'fashionable' of the alternatives yet the iron 32a was populer in its day and has a firm following and is making something of a comeback, mk1 concentric is carb of choice the only thing s i remember from off the top of my head are use the modern plastic float, and the needle lenght was critical 47.5mm been a good starting point

i used the modern 'greeves ignition and the bike was faultless the only down side was the flywheel was modified and needed a puller to whip it off unlike the std arrangement that comes off in your hand