I’ve been reading a few articles on modern 600’s and the power figures look good (around the 120bhp mark) torque is possibly a little low at 50NM but these figures aren’t to far off a late 90’s fireblade.
It seems these lumps are a lot cheaper than the 1000’s, I’m planning to make my own single seater at the end of the year, should I dump the 600 idea?
I’m thinking 300kg and possibly only 3 wheels!

If you can get the weight as low as 300kgs then yep why not, but I wouldnt use one in a conventional BEC weighing 400kg+, more because of strength than power

gearbox i think will be the weakness

If you've ever heard of Formula Student - they use 600cc engines and are effectively single seater track cars......

Various sprint / hillclimb singleseaters like Jedi's use them, and I think there is/was a race series for them too.

Yeah have seen a few formula students, what sort of weight are they coming in at these days?

Not too sure but if ou U2U flak-monkey i'm sure he'll be able to tell you as i know he's involved with the building of his uni's one.

We built a formula student car back in the uni days, it had a CBR 600 engine, for the competiton it had to breath through a tiny restrictor, but it spent alot of time on its bike carbs and was rediculously quick, and even on warm slicks struggled for grip alot of the time, (and that was with 4 wheels) great fun but to larey for a kart track and just plain daft on proper tracks 300kg at 120mph with no grip. the novelty wore off quite quick!

I did a theoretical comparison of my carbed R1 BEC vs a carbed R6 BEC. The gearing of the R1 is quite short, shorter than the R1, though the extra revs keep the shift point from 1st to 2nd at about the same speed. If you keep the weight right down to 350 kg or less then off the line performace will be not far off my slightly lardy BEC. Wind resistance eats into its lower power sooner though and slows it down. The top speed wouldn't be much less than mine though, because I would run out of gears at 120, where it would run out of power.

The cost of making a car that light would generally make a bigger bike engine the better option, as would the massive revs of a 600cc BEC on the open road (9000 + at 70 in 6th).

A heavier BEC with a 600 would still be quick - as quick as a pinto CEC which is still fast. You might be better off with the pinto though really.

All that said, low torque revvy engines do suit light weight cars. If you can make a car weigh less than 300 kg then maybe a 600cc BEC would be a good choice, especially if it was a more recent FI 600 with 130 BHP.

is there not some rule about a car weighing 300kg does not require a sva or something like that

I have a GSXR750 K1, 140 odd horsepower, 13,750 redline hardly any miles £550 gets everything

Cheers
David

I seem to remember the Jedi weighs around 275kg, so in road trim you might just get a 4 wheeler around 300kg, 3 wheeler - no prob