Topic: Anyone own or tuned a CBR250RR in the past - project decision made!

[lordmoonpie]

I was wondering if anyone has had experience of working on the CBR250RR four cylinder engine before and particularly the tuning of it? I've decided on my next project and it's going to be an RC162 replica, a 250cc four cylinder 19,000 rpm screamer! The donor engines come from the MC22 CBR250RR which I think was a Japanese only model later exported only to Australia so maybe some of our members down under might know (Terry? Retro?)

As it's a Honda four, I'm assuming I can do the usual stuff of lighten/balance crank, high comp. pistons, maybe new rods, hot cam....but then you start looking at the parts books and NOBODY offers any tuning options for them whatsoever. Any leads on tuning parts dealers would also be appreciated. I'm aiming for something at the end of it like the attached and will probably go the whole way on this one with Aluminium fairing too. I want to take a lot less time than the CR750 build though so am setting myself a target of one year. Might be a bit too major a target!!

Any ideas or suggestions gratefully received...

[kslrr]

I just did a google search, found the pic that is in your post and found the performance website.

http://www.phildentonengineering.com/category.asp

[lordmoonpie]

Yes thanks for the link - that's where the pic came from. Phil offers cycle parts but nothing really for the engine unles syou give it to him to do and then I'm not getting the experience, knowledge and fun, just the bill 

The search goes on 

[kslrr]

Doh.   I didn't read far enough on his site to see that.  Like you I would prefer to do the work myself.

[Alan F.]

Maybe some full ceramic bearings would be enough?

[lordmoonpie]

Donor engine has been located via Australia and Ireland - an MC19 CBR250RR which has the longer duration cams so that's a good start. I just haven't a clue what could be done beyond that for this motor, very little in the way of stock tuning parts advertised in any of the big tuning catalogues. Maybe I have to get them from Japan as they are Japanese market. Anyone know if we have any local Japanese members on here I can talk to?

[simon#42]

simon , before you start this project i would try and ride a standard one first . to be honest they are a dreadful thing all revs and no go . i suspect this is the reason there are no tuning bits for them . also unlike your 750 it wont be worth a fraction of the money it will cost you to build .   sorry to sound so negative but i have ridden a standard one. 

[lordmoonpie]

Ah but you're assuming I'm using common sense here Simon 
This is about something to occupy me relatively short term (I think it'll be a much faster build than the 750) and it's something I love the look of. It's all revs and 45 bhp so you're right it'll be a nightmare to ride and that's also something that I find kinda interesting, I mean when I've finished this will rev out at 20,000 rpm, that's gotta be a laugh even if it's just for the noise factor? I loved the challenge of riding my little Kreidler and that was *just* 16,000 rpm although its power band was 15,250-16,000 so damn hard to keep it singing.

As for value, I reckon I can build a really nice one for less than £10k....they're selling for between £18 and £20k as complete bikes believe it or not so I ought to be able to recoup my build cost if I sell....but that's not what I'm doing it for of course. Sam will probably back me up on the 750 costs - I think Chris's CR750 cost in the region of £16k to build and he added the provenance of a pile of sprint records to it and had to sell at half the build cost. I'm not sure there's any real money in building top end replicas with quality parts any more unless you have a reputation to sell on the back of like Mark and Vic world.

One day I'll do exactly as you suggest and use my head and not my heart in picking the next project LOL!

[simon#42]

well as your heart is set on it !    it makes a bit more sense now you have explained  [ not much but a bit ]
anyway if everyone let there head rule there heart it would be a very dull world indeed , good luck and be sure to keep us all up to date with the progress !!!

to be honest it sounds just the sort of stupid thing i would do myself !

[lordmoonpie]

Ha haaaarrr - just think of the noise through four open megas. I swear I'll be deaf as a post by the time I'm 50 but I'll have the biggest grin on my face you've ever seen

[ttr400]

Seems you must be reading my mind Simon, this bike is on my to do list..!! I just put my name on a motor a few weeks ago. There are quite a few CBR250RR bikes down here. I'll check around on prices for you.
Also I seem to recall there being a HRC kit parts manual for them, I could be wrong but I'll check it out anyway.
A guy in the classic race club built a replica a few years ago and normally parades it at meetings here. Jim Redman normally rides it when he is not jet setting around the world. I will be seeing them at the end of the month, so I'll find out if they did any engine mods. I do know it runs the CR flat slide carbs.
Here's a couple of pics of the bike with Jim Redman.

[lordmoonpie]

Wow, thanks Kevin! The carbs I was told to use on them are Keihin FCR41 flatslides - not cheap and very modern looking. The big shame about these is the barrels being integral with the crankcases so you can't easily make them aircooled. The yamaha FZR250RR has separate barrels though...maybe a chance to make an aircooled honda lookalike out of a yamaha? Sacrilige I know. Glad you're thinking the same things Kevin - we can share info on yet another build! 

[ttr400]

I'll do some checking around tomorrow...actually today. A friend of mine imports container loads of the grey 250's and 400's from Japan. I have seen the 250 Yamaha's and also the kawasaki 250/4.
Another pic for you.