SOHC.co.uk Forums > CB500/550

Twin Carb 500/4?

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Laverda Dave:
I would guess that's a lot of work making or modifying inlet manifolds, air box, cables etc for little reward but.....I do like the ingenuity of it so hats off to whoever did it for making something a little bit different.

deltarider:
Yeah, that boss of the motorcycle business eventually got rid of his CB550K3 because he never had the time to do it. In the past I've known a guy who had modified his CB500 to a 4-valve per cylinder one and had raced it.

badger_eng:
The bike is fitted with ''Murrays Carbs'', he's a bit of a legend on the Honda CX500 circles / forums. US based guy / outfit.

https://murrayscarbs.com/product/honda-cb550-carburetor-kit

I fitted his carbs to my CX500 build. Albeit it was two carbs for 2 cylinders. Ordered them on a Thursday night and the arrived Saturday lunch from the US. (Quicker than some of my local takeaways tbh!)

They are very thirsty items but do offer a small power increase. The CDI unit had failed on the CX so I replaced it with a Rae-San unit from Australia, this unit had various configurable settings for ignition advance via dip switches and one was basically to run with Murrays Carbs.

Most of his 4 cylinder offerings use a pair of Mikunis matched to shared manifolds. I cant comment on these but his CX500 VM34's were pretty good.

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TrickyMicky:
Firstly, I admit that I did not see or hear much of the video, But I thought it unusual to have cylinders 1 & 2 sharing a carb, likewise 3 with 4.  Earlier twin cylinder Hondas only shared a carb if they had a 360 degree crank because the intake and exhaust pulses were evenly spaced giving smoother breathing. Bikes like the CB72/77 and the later CB250 K series had twin carbs because they were fitted with 180 degree cranks which give uneven pulses.  The way the video shows the carb fitting means that each carb is supplying a pair of cylinders which are 180 degrees apart.  Many years ago Mick Hand sprinted a 250 supercharged Honda which was catalogued as a CB72, but it had a C72 crank fitted to obtain the regular intake pulses.

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