Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: MikeSB6 on September 25, 2015, 04:21:22 PM

Title: CB400F carbs
Post by: MikeSB6 on September 25, 2015, 04:21:22 PM

Hello,

   I've just bought an overbored 450cc CB400F engine and was going to have a set of carbs bored out to 22m and rejet. however, the carbs, which are standard as far as I know, have a 22mm bore at the engine end but are choked to a smaller vertical oval cross section at the slides. Is this normal for the CB400 and is it possible to increase the bore size on these carbs (I don't have an oval drill!)?

    Cheers, Mike J

Title: Re: CB400F carbs
Post by: hairygit on September 25, 2015, 05:05:53 PM

Most people on here using big bore kits find such drastic and irreversible actions unnecessary. You only need to mess with jetting if using pod filters or non standard exhaust.

Title: Re: CB400F carbs
Post by: MikeSB6 on September 25, 2015, 06:54:29 PM

Many thanks Hairy, I won't bother then,

    Cheers, MikeJ

Title: Re: CB400F carbs
Post by: hairygit on September 25, 2015, 07:05:43 PM

Good plan! The larger capacity pulls more air and more fuel through on the standard jets, so re jetting on standard airbox and exhaust is a waste of time, and money, far better to spend the money on petrol and ride it!

Title: Re: CB400F carbs
Post by: Dave_Canada on September 26, 2015, 02:04:35 AM

There's a fellow in Canada that bores 400F carbs. I haven't had it done (yet!) but reliable reports say it unleashes a surprising performance boost at higher RPM. Best to have an overbore kit and a mild cam to get the most from this.

http://www.denoonsp.com/services.htm

Title: Re: CB400F carbs
Post by: MikeSB6 on September 27, 2015, 07:56:28 PM

Hello Dave, thanks for the link-some of that NC stuff looks pretty delicious,

   Cheers, MikeJ