Topic: CB400f engine performance, what HP can you get ?

[jacksonc]

I was looking around at small carbs and saw that Mikuni makes a 24mm flatslide, but it looks like its only setup to be used as a single carb on a 1 cyl engine. All though it wouldn't be impossible to make a rack to hold 4 of them (unless they are too wide) I'm guessing you'd have to use some crazy 4 cable throttle like the original K0 cb750.

[rudi]

If some of you like to go the hard/cheap way ....
Mikuni Round Slide Carbs from Suzuki GS 750 # 24 mm and heavily converted
Kawasaki Z 1000 a Intake rubbers and all the neccessarry Headwork incl. 1,5 mm bigger Intake Valves

[turboguzzi]

You want a challenge? I'm just tuning my 250-4 engine, who do you think will get more power? 

I'm not familar with a 250 four street honda so I assume its a race/GP style bike, I know they even made a 250 six. I'm sure if its full on race engine you'd win in the power department  I'm not going to go all crazy on my motor as I said I just wanted to know more about the possibilities. Because I did a lot of searching on the forums and google and didn't see a lot of built up 400s to compare too. Where as its pretty well known what all you can expect from bikes like sohc 750s, gs1000s, etc. A couple of magazine reviews from when the 400 was new says it sort of flattens out after 8500 I was thinking the +1 camshafts available would probably liven up the top end and they don't require other heavy engine work.

No - not a race/GP bike well not yet
It's a CBR250-4 engine. As a tock engine it's pretty well optimised anyway but I'm going to try and squeeze a few more HP out of it. I reckon it'll be fairly comparable power wise to a 400-4 by the end of things. Sounds like you're doing the right things though Jacksonc - the head is ahere it's all at so focus on cams, porting, flow and that sort of stuff...

Hey TG - yes it's a CBR250, do you have any experience of these engines?

no, havent got any experience with them. Just came across one ages ago in new york, Jeff Elghanayan (ex Team Obsolete) had one, following the zillion revs howl on Brooklyn bridge is something i dont forget.... then saw tons of them in tokyo, that motor is used also on the Hornet 250. Bet there are tons of tuning parts for these over there, you'll just need a Japanese speaker who knows what to ask for.

TG

[Howell]

My tunerfriend builds also CB400 engines with 60 BHP at the rearwheel.
This is such an engine:
http://www.youtube.com/watch?v=RFJX2GVqxZI
http://www.youtube.com/watch?v=GUKve7XMj_4

[MRieck]

Very nice.