odgie

I write for 100% Biker, Real Classic (by far the very best classic bike mag you'll ever read), plus a bit for Custom Car and a couple of American hotrod mags. Well, it all beats working for a living...... Doubt I'll be up't north anytime soon though unfortunately. I gave up scrambling after wreckin me knee (snapped the cruciate ligament in that muddy slot at a scramble near Edinburgh a few years ago - but two ops later it's cool now though), still trials riding (just got a very nice 1932 JAP-powered girder forked OK-Supreme, won the Rigid class first time out last weekend), but do a lot of hotrodding and nostalgia drag racing now, plus a few VMCC runs (our kid's secretary or our local group). So too many busy weekends, not enough Odgie to go round.....

Yep, bang to rights on all counts everybody - guilty as charged.....

You have some of the right bits to start with, which is a big help. You can get your Bultaco sliders turned down in a lathe, and fitted into your existing Triumph sliders - that means your wheel will still fit straight into the bottom clamps, and save you the cost of Norton sliders (have you seen the price of those lately...?). Ditto getting your yokes machined out - they will still fit in the headstock using original bearings. But both those processes are tricky to perform - not a job for anyone who isn't well versed in lathe work. I believe the going rate around here is about 150-200 quid if you supply the bits, which you already have. I do my own, but I wouldn't like to do anyone else's - those last passes on the lathe when the alloy slider is down to about 1mm of thickness are a bit on the stressful side...

I've only ever used radiator hoses for all inlet tracts, including those where you join the carb to the head (ie, downstream of petrol flow), and never had any sort of problem - if you think about it, any under-bonnet hosing would need to be oil/petrol resistant. The one on my Sunbeam's been there for about three years now with no trouble.

Hi Pat, yeh, I used the board racers as my inspiration. If you're interested, Real Classic magazine is doing a 'Build-Up' series on the bike, Part One is in their latest issue. I photographed all the hand-made stuff as I made it, and the series will run over the next seven issues. It runs a treat, as you say, they are a quick little lump. I had to estimate the gearing, and it's a little low, it tops out around 50ish (no speedo...), but that's probably fast enough - have you seen the size of those brakes...?! It don't stop worth a d*mn, but it don't handle too bad, although with those rearsets you have to remember to pick your inside foot up as you bank over... Cool to hear from someone who rode the original machine. And yeh, lots of 'If only's...'

It's from a BSA Sunbeam scooter - a badge-engineered version of the Triumph Tigress. They made a 175cc two-stroke single, and a 250cc four-stroke twin. Barrels and crankcase are all one casting, with a removeable plate each end to carry the main bearings. There's a one-piece crank which has a large flywheel on one end (which carried the fan blades for the air-cooling) with the alternator inside it, and the clutch on the other end, with a gear primary to a four speed box (so the engine runs backwards...). Quite a pokey little thing, I have one in a James Comet chassis I built... Photos here: http://picasaweb.google.co.uk/odgie633/Speedster (I'm getting carried away with this photo thing now....)

Sorry it's taken a while guys, it's been a hectic few days... If I've done this right, there should be a few shots at this link... If not then Lord only knows where I've sent them to..... :-) http://picasaweb.google.co.uk/odgie633/BSASunbeam

I ride one I built with a BSA Sunbeam scooter engine (which is identical, just badge-engineered) in a Bantam frame, and it works a treat. I'd post a photo of it, but I've no idea how to do that.... :-)

Great bike to cut your teeth on! The little Bantams are quite under-rated, but they can be made to go ever so well. And they won't break your heart like lugging an Ariel around will... Welcome to many Sundays of FUN!!!! :-)

I think I've cracked it, these things are definitely Pre-65, so have to be legal. Watch out for me ploughing through the Scottish sections next year... :-)

Can't say I've done much with C15's, I built one for a girlfriend of mine a good few years back, but it was a bit of a wayward beast, and we didn't have the money to really do it properly. They ain't never gone be as chuckable as a James or a Cub, but like all things, a good rider on any bike will still beat an average rider on a trick bike. But then you'll get the good riders on a really trick bikes... (why they do that and then complain trials are too easy I'll never understand, just buy a rigid if you want a challenge, but I digress...). If you want the fun of doing the C15 (and like Charlie says, there is fun in it), it'll make a half decent bike, sure enough. But it's resale value won't be as high as a Cub or James, although its build costs will be similar, and you've only got to look at what everyone else is riding to see they aren't the most popular choice. On the other hand, you have the C15 for (I assume) nothing, which is a big point in its favour... I'm trying to answer your question, but only you know what you want it for - it is well worth the effort if you're going to get a good few years enjoyment out if it (and not be dismayed that it isn't the most competitive bike in the field), but for the same effort (and a bit more money) you're right to think you could also build a better trials bike. Hope I haven't confused you even more....... :-)

Ah, a good question... 'Easy' is a relative term in itself, depending on someone's ability... Can you cut frame tubes and weld them (you'll need to redesign the subframe for example), and do you know how to fit 'fiddle' internals into the forks, or make Bantam hubs fit into C15 forks/swingarm? Rather than think at this stage about the ease or not, you may want to weigh up the costs first, a pair of hubs respoked with alloy rims and new tyres is a good few hundred quid gone, add in alloy petrol/oil tanks and guards, new pipe an silencer, another big bunch of dosh for the fork conversion, new rear shockers, ignition system etc etc, plus all the fiddly bits you never even thought of (like 25 quid just for footrests, plus levers, cables, and an extortionate 60 quid or so for a fold-out kickstart...!). I wouldn't say C15s were any harder or easier than any other bike to convert - virtually all Pre-65 trials bikes are only converted road bikes anyway, but please work out how much you want to spend on the project first, it's really easy to find yourself getting the wrong side of two grand. My advice would be you'd have to really want a C15 to commit that sort of time and money to doing it. But that's just my point of view, only trying to save you gettin in over your head :-)

There is an option to make your own, if you have access to a lathe. Take the teeth off the old sprocket with an angle grinder (brutal, but case hardened teeth will kill any lathe tool), then true it in the lathe, buy a blank sprocket (cheap at any good bearing/transmission factors), bore the centre out, weld the two together. In theory it should then be case-hardened again, in practice mine never are, and my front and rear sprockets still seem to wear out together at the same time. If you're stuck, there a small engineering firm near me that does it, I could get a price for you (he doesn't charge me, because I do work for him in return), but if you haven't any lathe access there'll probably be a firm near you that would do the same, if you prepare the orginal sprocket first. I have a few photos of this process for a magazine article I did, I can forward them if that helps?

It's maybe worth knowing that, as you lower the overall ratio, either by final or primary drive ratios, you also in effect make the gears a closer ratio anyway (I think it's something to do with the lower the overall ratio, the less effect each gear change has, but don't quote me...). If you set the bike up for a very low first, that will as a consequence make second closer to it. A wide ratio box will give you a higher top gear, but unless you're doing much road work, it isn't really that important (how many times do you get flat out in top these days, with trials usually laid out quite compactly?). My Sunbeam has all the stock road ratios inside, and you can't lower the primary (it's gear driven), so I'm stuck with the 'cotton reel/dinner plate' type final drive, but it works fine enough. I've now got first low enough to make second also a useful gear (which of course is not always a Good Thing, as if you get them really close, unless you're An Expert, you end up with the dilemma of which gear to choose...) My advice for what it's worth would be to save yourself the expense and hassle for the time being, set the bike up with first gear low enough (and in my experience that's always a bit lower than you think you need it to be), and see how useful second then becomes as it is. In the real world, a bit of difference between the two will at least make choosing which for what section a simpler task, and you may find you don't need to strip the engine and spend a heap more money on it after all. :-)

I run a (heavily) modified D7 frame on my Sunbeam, which works quite well. If you drop me an e-mail at odgie633@yahoo.co.uk, I'll e-mail you back a shot and some details of what I did to it. :-)