Improving a Jubilee

Hello Dan,

That sounds a good use for a Jubilee.

The Roadholder forks are good forks but will be expensive to buy and then rebuild. Why not get some Japanese forks complete with clamps at an autojumble- on the grounds that they will be cheap to buy? I know someone with Honda 750 forks on a racing Goldstar and they are vastly better than the (double damped) BSA originals. I also know someone with Suzuki (air forks) on a trials Bantam. Now they are good and look the part as well.

They will not difficult to fit to the Jubilee headstock (provided you have access to a lathe and can make up your own wheel spacers etc). Jubilee front brake is pretty useless so probably best to use the Navigator brake drum and respoke the wheel into a 18" rim. I don't know what tyres are now available but I expect there's a better choice in 18". If money is no object use alloy rims and a twin leading shoe front brake. I think most trial's people like the forks to look British so put on some rubber gaiters.

As regards the exhaust I expect you will need to convert to two in one and have one high rise silencer - saves weight. As far as I know no-one makes a trials high rise system for a Jubilee so again you need to make your own front pipes - easy enough to weld up . I would use one of the short 'universal' megaphone (cheap and look good) style silencers and see how it works. I would think you will want to alter the foot pegs at the same time to get them further back i.e to suit yourself and obviously you want a single lightweight seat..

The Jubilee has a very tiny carb as standard so probably worth fitting a 7/8ths carb and you will need a fairly efficient air filter as well. The engine is probably highly tuneable but you want smooth power on a trials engine rather than top end.

Anyway good luck on your project. It will keep you out of bother for a long time.

Patrick.

Hi Dan,

Sounds to me that you already have a good idea how you want to go about your project. If you use the Navigator down tube then the 19" front wheel in the Roadholder forks should give you the same frame geometry as the Navigator and this was counted as petty good in it's day. That would give you a pleasant road bike but a bit short on horse power. And it keeps the bike pretty close to standard Norton.

Definitely for real offroad use you would need the 21" front wheel to get the extra ground clearance but as you say that would give rather strange handling for road use - a bit lacking on turn in I would think. On the trials Bantam it is usual to cut the top frame tube and reweld to get more turn in. Using your Yamaha forks sounds a good idea - I have Yamaha forks and twin leading shoe brake on my Jubilee cafe racer and they work well. But I cheat on horsepower by using a Yamaha engine - so 40Hp rather than 16. It's only a road bike though .

As you are already into racing you probably know that just occasionally the bike does land on the ground (a lot sometimes in trials riding) so thats probably why people go for the Japanese bits. They are cheaper to replace and readily available and maybe even better than the originals. And you could sell your Roadholders for a fortune.

It depends I suppose on your views of originality. How about a Jubilee with triple discs - I knew of a Goldstar being raced with triple discs,

What do you race in twinshocks? I was involved (oop in Yorkshire years ago) in road racing in the Forgotten Era category with a B25 Starfire and also with others racing a Goldstar.

Happy days

Hi Dan,

Your Yamahas are now legends in themselves and I can see that you are very much into Motocross as very distinct from old fashioned pre 65 Trials. The YZ250 is a real screaming two stroke that made Yamaha's name famous -close on 50hp from 250cc straight out of the showroom ! The two stroke power band is addictive - I had a LC350 a long time ago.

The problem with the Jubilee is that virtually nothing is available for bolt on performance improvements. In fact even service items such as pistons,valves etc are now hard to source and standard Jubilee bits don't exist at the autojumbles any more. They were always fairly rare even back in the late fifties/early sixties and as far as I know they didn't have much competion use ever. About twenty years ago there were a few 'LightweightOwners' in or around the Wiltshire area (Malmesbury Mafia?)and Andy Sochanik from Bristol area who knew a lot of useful information about the small Norton but they seem to have gone very quiet in the NOC. Andy is still listed as the Technical Adviser and he certainly knew his nuts and bolts. Hopefully someone else will put in an appearance and come up with some ideas. I now live in ireland and getting Jubilee bits here is impossible - Ebay prices can be ridiculous for what is often total junk.

Going back to fitting your Roadholders these will fit easily using the Navigator front down tube. It's a straight bolt on job using standard bolts and spacers but one minor item which you will have to sort is the top engine steady bracket. The Navigator engine is 1/2" taller so you will have to alter the mounting on the front tube to suit.

The original carb is 25/32" (less tham 20mm) and the flange mounting holes are 2" centres. The flange mounting Mikuni if I remember correctly is 48mm so its a few mm out for mounting even if you have one. Nobody I know lists a conversion kit to fit the Mikuni to a Jubilee but there are Mikuni /manifold adaptors to fit Bantams and Triumph Tiger Cub. So my starting point would be to first get the rubber carb adaptor and then see what Mikuni turns up say 22mm, maybe 24mm. The Jubilee remember is unusual as it is a four stroke twin so a Mikuni from a 125cc monkey bike might be a good starting point on jetting.

Both the Triumph Cub and the BSA Bantam are popular choices for pre 65 trials so someone such as Rex Caunt Racing , Leicester, could maybe give some specifics.The adaptor for the Triumph Cub I think is the most likely one. Another likely name is Allens Performance, Notts.

I know you want to go electronic ignition which reminds me that I got my Boyer Branson from Mick Hemmings maybe twenty years go and he was an exceedingly helpful person (as was Boyer Branson as well) so maybe he could help.

By the way I have three Lightweights;

A real 250cc Norton Jubilee standard model A real 350cc Norton Navigator De Luxe and the one that Norton should have made is the Yamton - thats the Cafe Racer Jubilee with the 400cc Yamaha XS 400 Special engine. It's definitely not a straight swop as it means cutting the top frame tubes and lenghtening by about 1" and welding in Yamaha bottom tubes and engine mounts, Amazingly they matched up very well and the engine ONLY just fits. Performance is good and very controllable. Top end if youre very brave is around 115mph and acceleration through the six speed box is better than standard Yamaha as the Jubilee is quite a bit lighter. It makes a lovely cruiser as it has enough go power and stopping power to keep up with modern traffic.

By the way I think you mentioned something about damage to your Navigator front down tube and the answer to that is yes they were well known for breaking around the engine steady bracket. So make sure you reinforce it around that point as it will definitely break if used energetically in trials.

Patrick

Hi Dan,

The heavy duty bearing in the gearbox casing bears on the sleeve gear shaft just like you said and in the parts list is actually called the Sleeve gear bearing. There is another small ball bearing to support the tailend of the main shaft and this is called the Mainshaft bearing in the parts list. This could allow excessive movement if it had collapsed.

I have stripped down four or five separate gearboxes (all the early type ones) and so far have never come across one with a collapsed mainshaft bearing so it's more likely just general wear on the sleeve gear bushes. Unless the movement was really bad or it made nasty noises I would be inclined to leave it and get the engine actually running first. AMC engineering wasn't total precision and you may be judging excess movement by Yamaha standards.

The sleeve gear bushes are plain bushes (two of them) and you need to strip the complete box to get at them. So I would get the engine running and test the gearbox under load - that way you can check everything out in one go. The common trick of this gearbox is to jump out of first gear when under load but a shim usually cures that - easy when you already have the box in bits.

Patrick