Author Topic: What's the difference between the CB550K3 and -F1/F2 airfilter element if any?  (Read 611 times)

Offline deltarider

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Can any of you experts answer the above question, asked on the German forum?
I myself have wondered what it could be, why there is such a price difference and why some elements have a smaller opening engine side. Compare for instance: https://honda4parts.nl/product_info.php?ceid=951d401791f5859aa5abf58e532fed03&sort=3d&page=5&products_id=3472&language=en&ceid=951d401791f5859aa5abf58e532fed03 and
https://www.cmsnl.com/search/?section=all&q=17210-404-670&tab=
« Last Edit: March 04, 2021, 12:27:48 PM by deltarider »

Offline deltarider

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Thanks Oddjob, I wondered if it possibly had to do with the K3's longer rubber boots (or is 'runners' the word?). As for the wider and smaller opening, clearly traders are lost...

Online K2-K6

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Thanks Oddjob, I wondered if it possibly had to do with the K3's longer rubber boots (or is 'runners' the word?). As for the wider and smaller opening, clearly traders are lost...

Longer rubber "bellmouth" ? is to influence lower rpm more than higher range.

The carbs, 4 pipe exhaust and intake would seem to be setup with torque at lower rpm in comparison to the F model that would expect to be ridden at generally higher range. Is the gearing different between the two?

Offline deltarider

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Longer rubber "bellmouth" ? is to influence lower rpm more than higher range.

The carbs, 4 pipe exhaust and intake would seem to be setup with torque at lower rpm in comparison to the F model that would expect to be ridden at generally higher range. Is the gearing different between the two?
The K3-ED 's rear sprocket had 34 teeth where the F had 37. In continental Europe the K3 was marketed as the tourer version of the somewhat sportier F (see ad below). I remember having seen that even an aftermarket firm had two airfilter elements in their program: for the F and the K3. The wider and smaller opening remains a mystery however, if you see what the traders offer as OEM.

Online K2-K6

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You can see the difference in the brochure figures with the F2 set to make it's BHP peak 500rpm higher than the K3.

You'd guess that the K3 intended use would be more accommodating of higher gear roll on throttle use,  rather than changing down and revving the motor, longer intake will help this. But it may give more and louder intake resonance (noisier when making wider throttle opening at lower revs ) which they've trimmed by altering the air filter.  A noise baffle in other words.

It's likely that the filters will flow exactly the same air mass but one would make more noise , sportier? and welcome on a more enthusiastically ridden bike,  but literally a pain if you want to tour around on long serene journeys. 

Honda were then absolute masters of intake tuning and show many minor tweaks to get things working how they wanted.

You could also view it as putting a very slight suppression "flat spot" into the F2 that gives more of a kick as it reaches that higher peak, and so give more of a sporting feel that matches with the lowered gearing.

 

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