SOHC.co.uk Forums > CB500/550

Carb Differences

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simonuk:
Hi
I have a cb550K and it feels a little slower than the 550f2 I had a few years ago. The current bike does have a 4:1 system on it but I think its a bit slow to rev. I have been told the carbs are smaller on the K model to the F2, is that true and if so can you fit them without messing with jet sizes?

Thanks
Simon

SteveD CB500K0:
If you mean the CB550K3 (four piper), it was actually faster than the Fs in all the road tests at the time. The carbs are completely different from the Fs.

However, if it has a restrictive 4-1 then it is possible that the mixture is screwed and it is making less power.

Bryanj:
Also if a K3 not easy to fit the F carbs as you would need everthing from the head backwards due to different spacing and i don't think there is room on the K3 frame

simonuk:
Hmm, it has a 'JAMA' 4:1 system on it, possibly does need rejetting. Has anyone experience of fitting a similar system on a K model and what the jetting changes were?

Thanks for help
Simon

z1100r:
Slow to rev is extremely unlikely to be the carbs....assuming they are clean and funtioning properly.

It is also very rare that you need to rejet  for an exhaust pipe. There is an awful lot of crap about changing pipes and having to re-jet - even on 2-strokes.

Your jetting is far more sensitive to airbox changes/leaks and I would start there. If K&N type filters are fitted then a complete rejet from scratch of the whole carb is required - and is an unbelievable pain in the arse aswell as requiring special equipment. Refit an airbox - makes the bike so much nicer.

I agree K3's are faster and more economical, they are also smoother and a lot nicer to ride. Its all down to a much better carburettor and exhaust system. The original 4 pipes were the best I've ever fitted to a honda 4 and worked great on all of the many capacity changes my bike went through. I fitted loads of 4-1 pipes and nearly every single one of them made more noise and was slower.

No matter what you do you wont beat Honda. They cast new manifolds and rubbers, swapped the carbs, and finely tuned the whole system making the K3 a much more refined bike. IMO

Which is why my 500-4 600cc bike has a K3 motor with K3 carbs and a std airbox...shame about the pipes, but I cant get K3 pipes anymore.

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