Honda-SOHC

SOHC.co.uk Forums => CB500/550 => Topic started by: matthewmosse on February 14, 2011, 07:14:34 PM

Title: Carb coversion to SU
Post by: matthewmosse on February 14, 2011, 07:14:34 PM

A long while ago now I read about someone who claimed 90+ mpg from his sohc 550 by fitting a Su carb and home made log manifold. Anyone else kow anything about this conversion and who did it, I'm thinking of doing this on one of my bikes, probably in conjunction with adding a 650 top end to one of the 550 bottem ends littering my shed.............

Title: Re: Carb coversion to SU
Post by: SteveD CB500K0 on February 14, 2011, 09:20:31 PM

I was in email conversation with Steve Scott earlier this year. He makes single carb manifolds for Goldwings and also CB/4s

Jessco Motorcycle Works
gl1000singlecarburetor AT midco.net
http://www.tinyurl.com/Jessco (http://www.tinyurl.com/Jessco)

Title: Re: Carb coversion to SU
Post by: flc on February 14, 2011, 09:47:53 PM

i have been looking at this for a while, still not sure have a look here
 http://www.britchopper.co.uk/forum/viewtopic.php?f=25&t=7075&hilit=collector (http://www.britchopper.co.uk/forum/viewtopic.php?f=25&t=7075&hilit=collector)

Title: Re: Carb coversion to SU
Post by: matthewmosse on February 15, 2011, 05:57:26 PM

Cheers, better try doing now - well sometime soon anyway, a good link there. I'll probly have a go at a diy manifold first since I've trained as a welder / metalworker and it's embarrasing not to give it a go........

Title: Re: Carb coversion to SU
Post by: daz on February 15, 2011, 06:50:28 PM

I have seen this done, a chap turned at at a vjmc night, he also by passed the oil way with an external pipe to stop the oil leaks.
It was about 3 years ago, not seen him since, Daz

Title: Re: Carb coversion to SU
Post by: K2-K6 on February 15, 2011, 08:56:32 PM

I ran Su's on SD1 V8 (think they are H1F from memory) Rover in rallying and got them to flow enough to give about 260bhp so one should easily be able to supply a bike at less than 130bhp.

Think they run with a fibre spacer on to the manifold to prevent heat soak into the carb, don't seem to have any problem with vibration, prefer the later type with built in float chamber for less components.

They can be run reasonably lean as the CV effect helps to make them richer during acceleration without altering basic cruising mixture, used thicker oil in damper tube to inrease this effect.

You often see them with bell-mouths on them, this is badly wrong as they need a small radius 6mm going into the venturi from a flat surface that extends 50mm away from the radius, then they flow properly to their maximum design spec. Used mine with pipercross foam filter fitted.

If you want any diags to explain these i'll try some scetches if you need them.