davetom Posted March 26, 2008 Report Share Posted March 26, 2008 Hi all, hope my questions haven`t been covered before but here goes...I fancy having a go at pre 65 Trials, I`m 39, and up til a few years ago used to do a bit of trail riding on a modern KTM,and often made the numbers up in Mid wales enduro`s. I`ve got a `65 C15 frame (road) and engine in the garage and hopefully this would form the basis of my bike. I`m ok with gas bottles,even better with angle grinders and brilliant at leaving chuck keys in lathes.... Q1.. Does pre 65 mean a `65 bike is too young or is it from when machine production run began? Q2 what sort of mods should I aim for that would leave me eligible to ride with majority of clubs( hope that isn`t too vague a question,I`m not after every mod,just what sort of spirit should I aim for..(I`ve got my copy of Don morleys 4 stroke book, Quote Link to comment Share on other sites More sharing options...
Guest majestyman340 Posted March 27, 2008 Report Share Posted March 27, 2008 If you know exactly what you are doing and have Quote Link to comment Share on other sites More sharing options...
woody Posted March 27, 2008 Report Share Posted March 27, 2008 Best thing to do is go along to the next two BMCA trials and have a look at what they are riding and maybe the Harry Perry Sammy Miller round next Saturday. The bikes range from near standard right through to highly modified. In the BMCA most bikes are only lightly modified as the sections aren't too demanding but can be a bit nadgery, depends who's setting out. There are one or two with frame kits, modernised forks etc. It will be a lot of work to modify a road based C15 for trials as you will need to consider things like ground clearance (lifting the engine and bottom frame rails) widening the swingarm for mud clearance, moving the engine to the left to get chain alignment and removing all unwanted lugs/brackets. Wheels will be big heavy road items, forks will be unsuitable for trials - and more I can't think of. The frame mods may not be too bad if your handy and if you're riding BMCA you will be able to use Bultaco/Ossa/Fantic/Yamaha or whatever wheels, it's not encouraged but no-one will really look or care. Similarly, you can get away with a pair of Yam or Ossa forks as they are in-line, not leading axle, so at least have a period look about them, especially if painted black. MZ forks also look period and can be had cheaply. C15 engine is fine in road trim, you don't really need a trials gearbox, just lower the overall ratio with the crank sprocket and final drive sprockets. I had the standard gearbox in mine until I found a trials box and it was fine. You can still get a trials C15 piston for a lower compression ration but I think the standard road ratio is probably ok. Or you can use Triumph 500 or 650 pistons to overbore to between 260 - 280cc but not really necessary - just ensure they are not too high a compression ration if you do. Whatever the quoted CR is for the Triumph piston, it won't be the same fitted to the BSA due to different head combustion chamber. Road cam is ok also but chances of finding a trials item is next to zero. Standard road head with 7/8" inlet is fine with standard valves. Amal 22mm carb - they may get twitchy if you have a foreign carb fitted. Biggest cost for the engine will be a rebuild if it is required but that applies to anything. If it is an early engine it will benefit from an Alpha big end and main bearing roller conversion to replace the bushed items. Ignition, there are various options, PVL is most popular at around Quote Link to comment Share on other sites More sharing options...
alan_nc Posted March 27, 2008 Report Share Posted March 27, 2008 Woody, Sure wish I had read your comments prior to spending a year trying to build a '59 street Bantam into a Trialer. Something about making a silk purse out of a sows ear. I competed all year on it but ended up working on it at home and in competitions far more than riding. Don't get me wrong, it was a great experience and I got the bike to the point where it was "almost" competitive. I'm riding a Sherpa T this year and I would have to say that you are better off starting with a purpose built bike. As someone said - You need to spend your time working on your skills not wrenching. Alan Quote Link to comment Share on other sites More sharing options...
woody Posted March 27, 2008 Report Share Posted March 27, 2008 Well. I'm not a bike builder so no expert on the subject, but that is what I'd be thinking about if I was starting off with a road bike. I know people have done it, but they're a lot cleverer than me when it comes to sorting bikes. Quote Link to comment Share on other sites More sharing options...
davetom Posted March 27, 2008 Author Report Share Posted March 27, 2008 (edited) Woody, thanks for your answers,I will try and get along to those bmca trials and take a look. As for the C15, I`m quite prepared to modify it, I enjoy that sort of thing ( my road bike is a BSA A65 I restored a few years ago so I `m a bit of a masochist anyway!),and the frame is bare at the mo and I don`t have wheels or hubs. I`m ok on engines and this one was reputedly rebuilt not long ago but time will tell.. Thanks for your input Majesty man but I just prefer Brit bikes. I`m only hoping to do this for fun,I know more modern bikes are better, I just like the way Brit stuff looks and sounds. Anymore info gratefully received..... Where is the Harry Perry round ? Edited March 27, 2008 by DAVETOM Quote Link to comment Share on other sites More sharing options...
pocket Posted March 27, 2008 Report Share Posted March 27, 2008 hi folks. On the same subject is it worth bracing the swan neck frame like they do with the cubs and while your modifying the swinging arm is it worth lenthening it ?? Cheers Steve. Quote Link to comment Share on other sites More sharing options...
woody Posted March 27, 2008 Report Share Posted March 27, 2008 Harry Perry is Saturday 5th April Steve, I'm no expert on frame mods, but my C15 has standard length swingarm in standard C15 frame, rear shocks are positioned to quicken the steering, it has Ossa forks/Mont 247 yokes, it handles fine, don't think it would benefit from a longer swingarm. Not sure of the reasons for bracing the swan neck - It's useful for mounting a tank and lifting it higher away from the engine. I've no idea if there are other reasons for doing it so can't help there. On the Cubs, the bracing also acts as an oil tank, Millers do a kit for that. Quote Link to comment Share on other sites More sharing options...
woody Posted March 27, 2008 Report Share Posted March 27, 2008 Personally I just cant see the attraction of Brit specials, when for a 1/4 of the money you can get hold of a reliable twinshock, thats nicer to ride, and far more versatile than a Brit special. One of the advantages of owning a Pre65 in this area, and it doesn't have to be an expensive special, is that the BMCA club has a trial every week for Brit bikes from September through to April. Twinshocks aren't allowed. There are no twinshock clubs in this area, Pre65 has a much bigger following. Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted March 28, 2008 Report Share Posted March 28, 2008 Hi Guy's, Woody's said it all realy, and take no notice of people that say you have to have a botomless pocket to build a pre 65 bike,you don't. You can have a plesant time finding the bits you need to convert the bike.I would start with a Otter type frame as it is exeptable in most clubs, and you will find that then most of the other parts are like compleating a jigsaw. And dont forget you can have just as much fun building the bike in the shed, as you can eventualy riding the bike. And you built it. Hope this helps with your disigion what to do. Regards Charlie. Quote Link to comment Share on other sites More sharing options...
davetom Posted April 2, 2008 Author Report Share Posted April 2, 2008 Thanks for all your answers,I`m off to the Harry Perry trial for a nose around Quote Link to comment Share on other sites More sharing options...
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