CB400F Performance upgrades

[Timmy Nizzle]

I have a custom CB400F '77 Cafe Racer. Its got most basic upgrades and runs great. The engine is stock, and in good condition, but I have an aftermarket exhaust and the carbs have been rejetted to match.

I'm thinking about squeezing a bit more out so my thoughts have turned to Big Bore kits, carb upgrades and Yoshi exhaust.
But all this stuff is super expensive now. There used to be good, cheap alternatives on Ebay but now it seems only the proper Yoshi stuff is around. Anyone have any tips, or stuff for sale?

The CB400F is a little ripper already. I would leave it as is unless upgrades are reasonbly priced. £700+ for big bore kit, and the same for Yoshi exhaust does not strike me as bang for my buck (Performance Parts). I cant even find the uprated carbs for sale anywhere, though a few years back they were available.

Thoughts and experience from the pros here is what I need! 

[hairygit]

Cruizinimage on e bay were doing big bore kits for 400 fours for less than £100 not so long back. They may well still do them. I have one of their kits fitted to my 750, and had no issues with quality, so worth a look.

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[Timmy Nizzle]

Thats what I mean - CruzinImage appears to have nothing for sale, possibly shut down. Did you buy from Ebay.co.uk or does he/she operate out of a different Ebay?
I would buy one of those kits if I could find one!

[philgresty]

http://www.ebay.co.uk/usr/cruzinimage_uk

Yeah looks as though they're out of em

[hairygit]

They'll re stock again in the near future I expect.

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[AshimotoK0]

Don't want to get into debate about quality but royhall (Roy) showed me the Cruzin intake rubbers on his lovely 350/4 on Sunday ... cracked all over and fairly recently purchased I think.
I pulled some carbs off a CB250G5 that's only done 2k miles and was last run in 1979 at the weekend and they were still nice & soft and no cracking whatsoever. This proves that it must be heat/petrol that hardens the standard Honda ones and that the Cruzin ones are basically not fit for purpose IMHO. Trigger is going to shoot me down over this, I know !!

[hairygit]

I agree about aftermarket rubber parts not being worth the hassle. But the big bore kits are certainly okay! (Trigger agrees on those!)

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[AshimotoK0]

I agree about aftermarket rubber parts not being worth the hassle. But the big bore kits are certainly okay! (Trigger agrees on those!)

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Is he still buying their rings  If you can't engineer a piece of rubber correctly what chance do you have with the complex metallurgy of pistons& rings but I suppose you pays your money and takes your choice. Their carb kits are crap too .. ask RGP750 !

[hairygit]

He's not said any different.

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[Timmy Nizzle]

So a couple of question to 400/4 owners:

What performance upgrades would you do and in what order to go from stock to maxxed out?

And which of those would you recommend as best bang for the buck?

There is a lot of info online but not in a coherant manner, nor very up to date. I just need a bit of a steer on my reserach I think as I know its not all about buying Yoshi bits to go faster.

[Zunspec]

Hello Timmy,

I don't have any specific advice other than there are several 400 based racers competing in the 500 Air Cooled class with the Classic Racing Motorcycle Club (CRMC).  There is a non-affiliated forum (Classic Motorcycle Racing Forum : http://www.cmrf.co.uk/smf/index.php ) where you could ask what these guys/gals have done to their engines and where they sourced their parts etc.

Cheers  Geoff

[Timmy Nizzle]

Cheers Zunspec. Ive posted over there as well.

[kevski]

If your bike is a road legal bike performance upgrades on such a small four don't really add up to much in reality as you are limited to speed limits, but if it's a track bike it's a question of money, how fast do you want to go?

[Zunspec]

Hi Tim,

Lots of useful advice being posted on the CRMC forum.

Cheers  Geoff

[Timmy Nizzle]

Thanks Zunspec/Geoff - you helped me hit the goldmine!