jon v8 Posted December 31, 2012 Report Share Posted December 31, 2012 I spent a very enjoyable afternoon in the workshop today doing a dry build of my HT5 gearbox with the new gears as supplied by Mick Ash.All fitted together beautifully,and was a joy to put together - till I got carried away and mounted the new Jawa speedway clutch to the end of the mainshaft..... Its too long by around 10-12mm,so the outer cover of the clutch fouls the end of the mainshaft. So my question is,from memory Sammy Miller used a shorter mainshaft to narrow his bike down.What were the standard lengths of shaft ? Mine is 1 and 1/16" of an inch from the end of the clutch splines to the very end of the thread.There is room to cut the end off the shaft and put a bit more thread on,(5/8x 20tpi) as the material doesnt seem too hard. I'd rather use a different shaft if one is available,rather than cut mine.And does anyone have a recommendation for other gearbox parts like layshaft bushes ? I could make them but if good ones are available I'd rather buy them. Quote Link to comment Share on other sites More sharing options...
trickymicky Posted January 1, 2013 Report Share Posted January 1, 2013 Hi Jon,glad you are pleased with the gears. Mainshaft lengths can be a bit confusing. The shortest one is the one fitted to the AJS and Matchless bikes with a GB gearbox. Overall length is 9 5/16". I have tried it on my Ariel project,and everything lines up nicely,but that is with the engine mainshaft shortened as much as possible. Most people prefer the one which is a little longer,however, yours sounds too long. I think Ariel did 3 different lengths (all longer than the AJS one mentioned),none are in plentiful supply now,so it may be easier to shorten it as you say,and cut more thread on it. There is mention of the different mainshaft lengths available here- http://archives.jampot.dk/Technical/Transmission/Burman/Burman_B52_Mainshaft_Lengths_(Oriel_OC).pdf But the diference in lengths mentioned appear to be of the plain portion that the sleeve gear runs on,not overall lengths.. Just bought some layshaft bushes from Draganfly Motorcycles,which seem fine. About £6 ea. Quote Link to comment Share on other sites More sharing options...
jon v8 Posted January 1, 2013 Author Report Share Posted January 1, 2013 Thanks Mick,yes - I'm very pleased with the gears,top quality. I worked out the changes I need to make to the sprockets to keep 1st gear the same as it was,need new crankshaft and rear wheel ones.Think I'll have a go at cutting some more thread on the existing shaft,worst case is that I end up with the old Norton clutch back on it. I'll get some bushes on order tomorrow.I'm very much looking forward to having more than one useable gear,plus a decent road gear too.Then its only the forks and possibly steering angle to sort out.... Quote Link to comment Share on other sites More sharing options...
jon v8 Posted January 2, 2013 Author Report Share Posted January 2, 2013 Success ! This afternoon I extended the thread on the end of the mainshaft with the aid of my trusty Colchester. All the other bits I needed are on their way from the very helpful and knowledgable John Budgen.Shouldnt be too long now before I can try out the new ratios. More studying of the links Mick posted, and other stuff I found on the net just go to show how many variations there are on these boxes. Quote Link to comment Share on other sites More sharing options...
jon v8 Posted February 3, 2013 Author Report Share Posted February 3, 2013 Finally got the Ariel to a state where I can ride it - what a difference ! I now have first and second exactly as I want them with a nice gap to third,which will be ideal for long muddy hillclimbs.All the effort too in making the Jawa clutch fit was worth it,ultra smooth,one finger operation and no slip.Just like a modern bike really.... For anyone struggling with a road cluster in a Burman box this conversion is more than worth doing,it transforms the bike. Quote Link to comment Share on other sites More sharing options...
trickymicky Posted February 3, 2013 Report Share Posted February 3, 2013 Good news Jon,glad you are pleased with them..Mick Quote Link to comment Share on other sites More sharing options...
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