Christmas present to myself !!

[RDfella]

Mike - that's what the sprag (one-way bearing) is rated at. Currently to start the project I use a mains-powered roller starter (guaranteed to start any race bike). 50% of the time it blows a 13A fuse when easing the bike's clutch out (in 3rd gear). 13A X 230v is around 3bhp, so I've figured from that a figure similar to yours. Given the initial shock load on a starter, I'd be happier with 200Nm. Either way, it's just not possible (unfortunately) to include a one-way bearing for my purpose. At least, not with the various options I've considered.
Pity, it would have made life a hell of a lot easier. Well on the way with the ratchet design, but it's throwing up several challenges.
Re belt issue - mine is 40mm wide, so doesn't leave much room for anything else.

forgot to add - very neat and professional conversion shown by John in that pic of his. Unfortunately I can't go that route because I have an idler tensioning the belt in that area and my gearbox (plunger type) is bolted to rear of engine thereby precluding mounting anything behind the primary case in that area.

[chaterlea25]

Hi RD
I was searching the web for starter ideas and saw that a Honda gold wing has a chain drive from the starter to a sprag  sprocket that looks to be a decent size
The other starter I saw was for AMC singles where they fitted a large gear to the clutch basket and a starter mounted on a new modified primary case.
A friend did something similar on a vintage Ariel , at first with a scrap yard Honda starter, these do not have a nose bearing
A after some time it was struggling so he went and bought a new pattern starter
This one has an internal gear reduction
It now spins the engine over easily even against compression

John

[RDfella]

Thanks to John and others for helpful suggestions. I discounted driving the clutch - first of all there's hardly enough space to achieve the usual reduction of around 15:1 by running a starter bendix onto the clutch - made even worse by the fact the clutch would drive the engine faster. I played for a while with the idea of getting a bendix to engage with a gear mounted on the crankshaft but eventually discounted that because it was becoming impractical for several reasons. Seems the only viable solution is a variation on what most others have done for A series, Gold Stars etc. I'm currently trying to complete a ratchet to sit outside of the engine sprocket which will in turn be driven by chain from a layshaft above the primary case, the other end of the shaft being driven by a Honda starter motor via a spur and set of bevel gears. Pic of ratchet progress attached - currently struggling trying to find the best way to spring-load the pawls (there'll be three when complete, currently using the alloy master for development). Not much room in there!

[chaterlea25]

Hi RD
That looks like a good strong device, I hope you can get  the rest of the bits together and working

John