I'm currently in the process of getting my street MC21 R ready to race in a 250 series we've got here in aus. Its basically a produciton series, limited in what can be done to the bike, needs stock ignition, suspension, chambers etc. I've been given allowance to keep the delimiting (which is already done) so that it's a more even playing field, 250 strokers (especially cheap ones) are hard to come by down here. No gp bikes/engines, and no HRC style parts

There's a couple of questions i'd like help with to get my old baby going as fast as the aprilia RS250s (i'll be the only jap 250, trying to convince a few other nsr/rgv owners to come along!):

As said above, i have an R model. Is it worth trying to buy some SE/SP adjustable suspension. or just get what i have professionally sorted (needs to be from an NSR MC21). Can i just use SE/SP caps in my R forks to make them adjustable?

Same question re engine, is it worth trying to source an SE/SP dry clutch engine? Is there any differences in ratios etc?? The cheapest i've been quoted is $2000 AUS (approx £800) which isn't much lest than i paid for the whole bike!

Finally, i'm currently running with no airbox, just 2 pod filters (jetted to suit). Am i better to get an airbox/filter and do the intake hole mods? I guess i'd need some dyno time to get it re-jetted

a basic overview of the rules: http://www.mrrda.com/2007-250-production-rules.php

All and any advice is much welcome, especially if it's not going to cost me much!!

You can't just buy the se/sp caps for the R forks. basically the whole for is different. Suspension is most important so buy the best you can.

You can probably live without the dry clutch.

If you had the money and time to find them, you could probably get away with buying special F3 parts. They were special racing bits made by Honda, but not under the regular HRC program. Rare as hens teeth though.

You might consider Magtek wheels if you can find them.

You should have no problem making the same or more power than the Aprilias.
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Just to add, the SP/SE and R motors share the same ratios, so no real benifit there. The dry clutch may make a difference to bhp, but only 1/4 - 1/2 bhp. So stick with the R motor.

Good luck

If your not bothered about mod'ing it too far the only things you really need are.

Ditch the oil pump and tank. It gives you alot more space and makes almost everything easyer to work on.

Get an SS/SP HRC harness and delimiter. This will let you ditch the lights and makes the wiring very simple.

Find SE/SP forks and shock, make sure they are in good nick.

The rest of your money spend on brake seals and chain and sprockets. Its easyer to find lost hp though getting everything running sweet like sticking brakes and worn out chains than it is getting inside the motor.

After that you could a lightened fly wheel and other such lightened parts from NSR-World.
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If I have to take the carbs off once more...

thanks for the advice re the forks and gear ratios.. the wrecker i spoke to said the R, SE and SP engines all had different ratios (which i didn't think was the case). I think i may just leave the engine for now and get it cornering nicely first

i should have mentioned that there's not much you're legally allowed to do engine performance modifications wise. can't touch engine internals, basically all parts must be from roadgoing versions of the same make/model. The rules are a lot different to the formula 250 series you have over there. the 250's are lapping about 10 sec a lap + slower than 400's on a 1:50 track

bj wrote:i should have mentioned that there's not much you're legally allowed to do engine performance modifications wise. can't touch engine internals, basically all parts must be from roadgoing versions of the same make/model. The rules are a lot different to the formula 250 series you have over there. the 250's are lapping about 10 sec a lap + slower than 400's on a 1:50 track

Maybe, but the front running NSR in F250 is an all but std bike, he ran (with under 60bhp) within 2 seconds a lap of a claimed 90+bhp FZR400, a couple of heavily modded (80+bhp) ZXR400's and a real RS250 GP bike.

On a very similar spec bike I was 10+ seconds per lap back

I've said it here before and I'll say it again, at normal club level a good rider can put a std bike pretty much on the pace.

Even at World Supersport level all their mods are only worth about 3 seconds a lap (The R6 cup is std bikes, WSS is massive money mods allowed they're not that much slower, ditto Superstock compared to WSB).

After all there's only around 10 seconds between the 125's and MotoGP bikes, if in your races a standard 250 is 10 sconds behind a standard 400 the 250 rider is to blame or the 400 rider is Valentino Rossi.

Anyway a std piped, std ignition NSR is good for 60+bhp.
You'll get better mid range with an airbox with a couple of 1" holes in the lid but a couple of bhp more at the top with open carbs or the lid off or pods. Horses for courses really.
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fontyyy wrote:
Maybe, but the front running NSR in F250 is an all but std bike, he ran (with under 60bhp) within 2 seconds a lap of a claimed 90+bhp FZR400...

Is that a claimed 90+hp or a claimed 400?!

When a modern 1000 is only making 180~200hp, I'd eat my own left arm to see a 90's 400 making that kind of power!
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Mate, I've said the same on the RGV forum myself to Sam (from BDK) see here but trust me, that FZR is properly quick. It's a good match for the ZXR's and their 80 odd bhp is not in doubt.

Dean (on said FZR) beat 4 RS's and a TZ in the Open, only Dan (on his RS), MJ and a young Stuart Mitchell (on an RS125) were within 15 seconds of him come the chequered flag.

I'd read all the posts on the RGV forum with guys moaning about them (all the "400" diesels), heard Bill complain and even seen Leighton (in VJ23 era) on TV being shot to bits by them, however nothing but nothing prepares you for them, they go more like 600's than 250's.

I know Wayne was blown away by their speed.

And that modern 1000 that makes 180 bhp will do it year in year out, no one is claiming these 400's don't need a rebuild every year or so which is probably going to be around 1500 miles at the most.
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A good rider on a 400 should be able to beat some GP250`s.
My mate Neil Petford came 2nd & 3rd at Croft in the open GP class on a ZXR400 in 1996. It was a New Era meeting, so had quick boys racing there. Was just after I`d retired from racing. I remember it was embarassing when Brenda Scyvier ( think that`s how you spell it), came over & apologised to Neil. The 250 boys had complained that he`d been awarded trophies meant for the GP250`s. Made me laugh when the riders came over to take the trophies from Neil, he told them they obviously deserved them, after being beaten by a pretty much stock 400 road bike!
He was bloody quick though, the git always beat me!
I was going through a funny patch, also was using Michelin TX HI-Sport road tyres which a sponsor supplied free but were sh!t. Switched to Dunlop inters for the next year & started to get my confidence back. Went faster in the damp conditions at Cadwell than I did in the dry with those shite tyres on. Would be nice to race against Neil again & see if I could hang on! Funny but, I`m faster now than I was then. Got my head sorted.
Anyway, he still holds the 250 lap record round Cadwell full circuit (before they put the new chicane in), when he won the Steve Machin Trophy race. Beat a £40,000 Aprilia race bike on his TZ250A, same as I had. He always was a nutter, still is!

A couple of HP is hard enough to find... 10hp+ with no capacity increase... out of a motor designed in the 80's?! Whatever.
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I'm sorry but I would have to verify that figure myself on a dyno 'I' used... I said this about the last time this particular 400 was mentioned and I stick by it. It just doesn't make sense... And don't forget the 180bhp of a modern road 1000 is at the crank, nay, piston crown probably! more like 150ish at the wheel from what I've read, so infact would be making 60rwhp as a 400... How old is the FZR engine again?? 1993?

maxim wrote:Hmm... Personally I think that's a bit far fetched. It's not unknown for pub dyno operators to 'adjust' certain settings to artificially inflate outputs.

If their bike's that good, then great! But that engine is making 235bhp per litre! And that's at the back wheel supposedly. So take transmission losses of around 10% and that their motor is putting most bikes on the MotoGP grid to shame for specific output, at around 250bhp!

Maybe WCM, Roberts, Suzuki and Kawaski should talk to them

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I've seen a very good engine builder get very high 80's out of a 450cc with the 400cc making high 70's.

My old ZXR400 race bike was full of special Jap parts and made 76hp if I remember correctly. The specs actually quoted 83hp or something, but I think that was measured at the bottom of a bottle of Sake.

A CBR250 is supposed to be making 40 odd horses, and they actually feel quite quick once you get them spinning up, so there's probably no reason why you couldn't get a 400 up to 90hp if you had an endless supply of cash for trick cranks, rods, pistons etc etc, and 20,000 rpm to play with.

Best results I've personaly seen is a ZX400 F3 making 78hp. Very rapid. Running the full kit as well as FCR's and a ram air box (as they all tend to these days).

While the NSR (and a few RS's) struggle to make thatsort of power they are both that bit lighter which does go in our favour.

I think Honda claim 75ps from their TT-F3 kit for the NC30.
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If I have to take the carbs off once more...

Yes, the ZXR400 is a bit of a weapon. However, I reckon that I used to be reasonably handy round the local Bira circuit and I couldn't get the boiler within a second of the NSR. It was fast for sure, but not as nimble as the lightweight stroker.

1:07.3 on NSR250 SS spec (like F3). Surface not too good, very bumpy.
1:07.0 on NSR250 SP. Resurfaced.
1:08.1 on ZXR400 F3 spec.

As comparison:

1:07.0 on '99 R6, 600 Stocksport. Easy. Then fell off
1:06.5 on '98 R1, 160hp missile. Push it round corners, darkies down straights

So there we have it, youre riding the F3 lol
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If I have to take the carbs off once more...