Topic: cb550 air filter cover

[jonda500]

I've been unable to get hold of a top part for the air filter housing on my 550F, and I didn't really think it would have a big effect any way.

Today I fashioned a sort of a cover by taping a small tupperware container over the top of the air filter housing so as to limit the amount of air available to the air filter. The difference in performance was profound!
The bogging down under full throttle is gone, the extra crispy exhaust note is gone from the mids and it sounds smoother/quieter. The flat spot just off idle didn't improve any however.

So then I screwed a short piece of pipe into the end of the straight through muffler to reduce the diameter a little so as to try and emulate the back pressure of an original ss muffler. This seemed to cancel out the good effect that limiting the air was having- the exhaust note sounded terrible - kind of a crackle pop extra crispiness - I couldn't get the reducer out quickly enough!! The air limiter I will leave until I rejet to suit the open top air cleaner better (change main jet from 98 back to 100)

[Frostyboy]

I wonder if this old post will help you along?

http://forums.sohc4.net/index.php?topic=75361.msg839480#msg839480

[goldarrow]

If you really really want one, I'll dig in my parts bins, I'm sure I've  one around.  Let me know

[jonda500]

Thanks Frosty- It's good to see a pic of my missing part and I feel better knowing someone had the same probs as me ... and probably has solved them.. ?

Goldarrow, I would really like to get hold of one- if you come across one, work out how much money you want to send it to me in Australia and pm me (-and then send me a paypal invoice?), thanks, John

[goldarrow]

I probably won't get to digging in until weekend. 

[Duanob]

LOL I think i got the last one. I scored the horn with a box off of ebay for $15 delivered.

I've never tried this but I wonder if a 550K topper would work. they are more useful as they are a tool tray as well. I see those around often. If it wasn't winter and my bikes were not all bundled up I would do a swap to see they fit. There are just enough differences in the F and K models that you never know.

[TwoTired]

Today I fashioned a sort of a cover by taping a small tupperware container over the top of the air filter housing so as to limit the amount of air available to the air filter.

Far more effect than "limiting air" is the pressure change caused by such a feature.

The inlet "restriction" impedes the equalization pressure destined for the carb throat, and the carb's jets flow fuel at a rate determined by the throat pressure difference relative to the outside air.

In effect, more of the vacuum sourced by the cylinders reaches the carb jet exit ports, by restricting the air inlet.  In fact, this can occur with the very same volume of air.


Exhaust pressure changes alter the oxygen demand of the cylinder, by disallowing space for renewal.  Also, some of the unburned hydrocarbons are not evacuated from the cylinder.  To run nearer stoichiometric, exhaust back pressure creates less need for fuel and more need for oxygen replacement.  Some might call that "leaner carbs".


Air movement and pressure changes are two sides of the same coin.  One does not occur without the other.

[jonda500]

Thanks TwoTired - we are lucky to have you - that explanation helps me understand much better why the air restriction is making my bike run so much better(so different)! -and why standard settings can only be expected to definately work well if you have stock standard exhaust and air intake systems.

[goldarrow]

Found one for you.  Pm me if still looking for one