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What is minimum cylinder wall thickness?
Posted: Mon Mar 26, 2012 11:25 am
by Anders F. R.
I still have this idea in my head, to bore out a Model G 350 engine to closer to 400 cc. If I can find a suitable piston, of course, and a cylinder that will need reboring anyway. If I go from 70 mm bore to 74 mm, volume will ingrease from 346 cc to 385 cc. That might provide some more low rev torque.
However, with a 74 mm bore, the minimum cylinder wall thickness will be only 3 mm. Is that safe?
And then there are those questions about the bottom end, will it take the (hopefully) increased torque etc. etc.?
Regards, Anders F. R.
What is minimum cylinder wall thickness?
Posted: Mon Mar 26, 2012 6:51 pm
by Geoffers
Hi Anders. Our host, Mr Hitchcock, sells a replacement long-stroke crank which raises the capacity to 400cc with the standard bore. It's meant to give much-improved bottom end power which is just what you're looking for.
T'aint cheap though...
Cheers,
Geoffers.
What is minimum cylinder wall thickness?
Posted: Mon Mar 26, 2012 9:31 pm
by Anders F. R.
I think I have seen that long stroke crankshaft before, but I can't find it now. Have seen a 350 to 400 kit, at least.
Anyway: This is for the350 Bullet, isn't it? I have an older Model G, not a Bullet. Don't think it will fit.
Correct me if I'm wrong! I have a spare engine, and if I could have a long stroke crank in that one, without doing too much irreversible end potential damaging things to it, that could be interesting.
400 cc from a 70 mm bore. That will need about 104 mm stroke..... Really a long stroke engine!
Regards, Anders F. R.
What is minimum cylinder wall thickness?
Posted: Tue Mar 27, 2012 8:57 am
by Geoffers
My apologies Anders - it is indeed for the Indian 350 only (page 43 of the current catalogue). Sorry mate.
Cheers,
Geoffers.
What is minimum cylinder wall thickness?
Posted: Tue Mar 27, 2012 8:42 pm
by Dennis C
Hi Anders
I have a BSA B31 350cc which I fitted a Triumph T140 piston to this brings the B31 to about 410cc and higher compression, the difference was barely noticeable which was quite a surprise, luckily I had a set of Gold Star Clubmans cams in the garage so I fitted these as well, now that really made the difference so much so that I changed the engine sprocket from 17t to 21t.
What was a 75mph bike is now a 95mph bike which will cruise effortlessly at 70mph.
But to be honest I think a 3mm cylinder wall may be pushing it a bit close, but I dont think the bottom end will be any problem