Hello to everyone!
I've just come back to this website, it got updated while I was in the Falkland Islands and it has taken me a few weeks to get back on.
For those who don't remember I'm Steve who has built a 400/600 conversion the hard way to race in the Bemsee Thunderbikes. Basically I had to build the engine in the 400 engine cases and I also kept the 400 flywheel so mine revs to 14500 rpm :D
It makes 88bhp at the back wheel and has 41lbft of torque.
I was racing it at brands gp a few weeks ago, I came home with one dnf a 15th and 2 12ths. I was gutted not to get in the top 10, I was running 8th in one race until i ran wide and lost my drive up the hill on the last lap
I will post pics soon as I'm in work atm.
Can I just say Loving the fact lots of you are making the 400/600 conversions. Since I have an 89 3tj frame in the back of the garage i'm thinking of a 727cc for next season for racing as my bike doesn't really have enough guts, but is overweight by 15kg for the regs
http://www.thunderbikeuk.com/rules.php

hi !

hybrids are cool ...

i'll have a look at the regs,, but would a zxr400 with zx6r engine be eligible ?

just, it'd be a LOT easier to finish it as a racebike .. lol

115bhp last time it was on a dyno :)

If you can fit the 600 crank, barrel and pistons it the 400 engine cases you can indeed race it. With the FZR it just bolts together apart from the crank seal :D although for my bike next year running the longer throw FZR600 3he crank i don't think I have that problem.
Add that crank to a thundercat top end overbored 3mm and you get 727cc, I'd hope for 100bhp so the bike would weigh 180kg, only 7 more than it weighs at the mo but hopefully lots more torque cos the 748s & big bore sv's just park on the apex and bounce out while I can run stupid amounts of corner speed in comparrison.

the 727cc fzr6 that pb built back in the day made 108bhp @ 10,750rpm and 57.2ft-lb @9250

http://fzr600.co.uk/

looks like my 4/6 wont be eligible if cases and frame have to be the same model

Well you could always ask if they would let you race it as there is an "in the spirit of thunderbikes rule" where the guy in charge of the series will let some specials in
Also what year is your bike as 4 cyliders should be before 93, I'd love to see more of the 400/600 conversions out there although yours is prob a bit cheaper to make than mine!

hmmmm, maybe worth asking then..

the frame is a 1991 zxr400L, engine is from a 1995 zx6r

cheaper ? maybe .. depends how good you are with a tig as its all new engine mounts to get the lump in the frame.

Ah rather than using the plates like a lot of people have i got the top mounts moved. This is because the engine is designed to bolt flush to one side of the frame and because it's a bit stronger than the plates and I can also use crash bungs as I crash a lot.
So effectively those people using the plates have the engine ever so slightly out of line with the frame, i very much doubt it is enough to worry about or make any effect on chain run ect but I'm very picky. Think I cost me about £150 to get the mounts moved.

Hi Steve.
Welcome back from the falklands, how are the penguins?
Thats an interesting point about the engine being slightly out of line using the mounting plates. When i first offered mine into the frame i had my suspisions but when the rear bolts were nipped up it sat more or less central. It also explains why the carbs are slightly to the right. I dont think its much of a problem though and the chain seems to line up ok!
Im really interested in the 727 rebore. Keep us posted with the progress!

It was too cold for the penguins while I was there, only the old ones were left as the others had buggered off to slightly warmer climate.
Well regarding the 65mm pistons, i know JE make a set but they cost £400 for 4. I'm trying to source them cheeper (my friend thinks he can get wisco to machine some from 65mm blanks for less than that), I need to rip my other thunderkitty motor to bits to measure the gap between the pin and the crown. If I can get some with the pin 3.48mm closer I have no need to run a spacer gasket, if not I need a spacer gasket of 3.48mm + standard base gasket of 0.25mm to reduce compression down to 12:1
If I can't get the pistons I will be making a 660cc conversion anyway as I have an old FZR6 crank sat under my bed.

under your bed,
That's devotion for you !!!