i am currently mocking up the running gear for my kitten. the engine sits just behind the seats and the rear axle will be a de-dion set up,my question is this: does anyone see a problem connecting the bike drive flange directly to the sierra diff ? as the diff and engine will be all fairly solidly mounted,cant think of any probs but its worth asking. fits a treat though and the suzuki tl 1000 makes 120bhp and my little kitten is 490 kg should be a hoot!

diff flange straight to prop adapter? conceptually maybe OK & you could lose some of the mounts on engine and diff, but practically difficult - how would you get the bolts in? Realistically you'd have to have a short (1.5"?)solid prop, The prop flange is now reacting wheel torque, which it's not designed for but might cope. The gearbox output shaft is being used as a engine mount too though I think this bit of a bike must be really strong to cope with chain tension.
So I reckon it might work but it's a necky innovation! I don't think I'd risk it - I'd go the normal chain drive middy way - much less transmission loss too!
cheers
Bob

i have got some wiggle room so i could use a buffer of some kind i was thinking of something like i used to keep changing on my old imps every other week ,donuts i called them but something like most fords use as i dont need to use uj,s ive got about six to seven inches to play with perhaps thats a way to cushion shock loads etc? im using a 3.62 diff and it will run on 10" wheels so the gearing is quite low and on 165,s so not a lot of rubber to fight either.

this has been discussed before. Id not heard bobs take on it, but in my opinion you wouldnt be able to start ditching engine mounts etc, and i think you would need some compliance in the link - probably a rubber ring, or a pair of u/js. You would be hard pushed to line it all up perfectly straight anyway, and the engine will always buck slightly under load.

thats a non starter then after doing the gear calcs again its giong to have to have a step up gearbox in the trans line as its geared to do 48mph at 6000rpm without it.i tried my mates tl1000 this morning riding along at 50 at 6000rpm with straight through cans on not pleasant! allens do a gearbox but im not sure howmuch it will raise the gearing .the car is on 165/70/10s with a 3.545 diff and a primary reduction ratio of 1.838. the gear box comes with a 1.4 ratio but im struggling to figure out how much that will raise the gearing?

bobs advice allows you to pick any final drive ratio you want, because you can change the sprockets.

if its dedion, cant you pick a diff with a lower ratio?

i know hes right but the only way the v twin will mid mount is side on as you would put a four cyl unit into a seven with a propshaft so the engine will have to go under the bonnet and it looks like it will go in with a bit off trimming of the passenger footwell. its all down to me refusing to put bigger wheels on it but it looks great on its little wolfrace slots! i have got a 7" sierra diff with a 3.15 gearset but its for my mk and it wouldnt help matters much anyway so il wait to hear from allens in nottingham on monday and hopefully their rev up box will sort me out .

I think the step up boxes only gear it up by about 1.15 - 1.2, will that be enough?

according to the allens website the "rev up" gearbox comes with a choice of ratios from 1:1 to 1.4:1 now to me that looks like a 40% rise in ratio but my maths is w**k. if im right then that gives me 12.5 mph per 1000rpm in top.not great but it means 60mph at 5000rpm which i can live with.