Hitchcocks Forum

Without going to extremes does anybody know what these can be bored to and what high comp piston to use. I put the crank in this one together using 500 wheels which are about 1kg heavier and so far it is performing well, just want a bit more get up and go out of it

Hi Norm,
I have used Meteor Minor Sports pistons in several 350's I have tuned and also shortened the cylinder barrels, this combination usually getting close to 10:1 C.R. My own Indian 350 is modified in this way and also has some cast off cams from our 350 racer in it and ported head etc. It goes ok, but is not as fast as I want, probably getting close to 80 mph flat out, so more work is to be done. There is a point [around 10:1] where things suddenly liven up a lot with the 350 and I think this machine is just shy of that at present, my Father's Redditch 350 is just a shade higher than mine on C.R. and has 'R' cams, this machine will reach a genuine 90 mph. I am not sure I would use the 500 flywheels, these will rob you of performance and power. I lighten the flywheels by a few pounds in the 500's I tune for more power and much faster accelaration, so a 350 with 500 weight flywheels will be at a disadvantage in that respect. It is possible to go beyond the +0.080" oversizes commonly available for the 350 piston / bore sizes, +0.060" is the maximum permitted oversize in the BHR racing regs and most others and this gives our 350 racer an actual capacity of 361 cc. Cheers, Paul.

I think you can get the 350 out to near 450cc by using a BSA B40 piston, which according to Google is 79mm as opposed to the 350 Bullet's 70mm. I am not sure if this requires modification or replacement liners, you would have to check the thickness of the spigot. I think a company called Tollgate Classics do this conversion,I believe he is a one man band, he does have a web-site, but I'm not convinced that he has fully embraced the electronic age though.
As far as the flywheels are concerned I wouldn't disagree with the comments above as far as out and out performance is concerned, but I have a 1956 350 Bullet engine fitted in a trials bike, that appears to have left the factory with a 500 bottom end, similar to the ISDT bikes. I'm not sure how heavy the flywheels are, but this engine has lots more "plonk" than my Indian made 350. I would go as far as to say that I don't think I have ever stalled it and it just chuffs away off road. Again be wary of ultra high compression ratios as the search for power can have an adverse effect on an engines characteristics, especially if you can't find decent petrol. It very much depends on what you want to use the bike for.

Thanks Paul and John. Paul I put this crank together a few years ago but only recently got it finished and up and running, but from memory, one of the reasons I fitted 500 wheels, apart from the fact the Indian ones had had the drive shaft welded in, the Indian 500 wheels weighed the same as the 350 Redditch ones. Redditch ones same diameter but thicker

Tollgate get them to 450 but with a new liner.
Click Here

Ha! clever hyperlink didn't work - do it the old way
http://s236652202.websitehome.co.uk/350to450.htm