Performance air filters...oh, and an unusual teehthing problem....

[singleoverheadbraincell]

Hi everyone,

just signed up here today after getting a 1977 CB550k...just undertaking a bit of tune-up work and was interested to see on 'wemoto' that they had power cone air filters to replace the stock item. (Now, I am trying to keep this bike as original as possible and this is the only modification I intend to make). The filters do look good, the chrome I thought would complement the bike well. I recieved them promptly and after wrestling the air filter box out of the bike (you need to remove the battery holder unit to do this) which wasn't that easy I realised there is no way they would fit onto the carbs serving cylinders 1 and 4 without fouling the frame. Anyway, wemoto have agreed to refund me but did say that they have sold the same filters to others without any hassle, which I don't really believe. There are other filters available at various other places but I was wondering does anyone have any experience with fitting and using these. I presume I will have to re-jet to something bigger to keep the fuel/air ratio correct?

On another note, the teething problem I refer to above was a faulty fuel tap which wasn't working in the reserve position. I spent two days trying to work out why the bike was running very rough (spark, check - compression, check - petrol, check, or so I thought). The fuel tap was very tight and took a pair of pliers to move and it was my intention to overhaul this anyway but as a last resort I decided to drain the tank and put in fresh fuel just to eliminate the potential for the fuel to have lost some of its properties through sitting for a while. It was only then that I noticed that, in the reserve position, the fuel was not leaving the tank. Eureka moment for me and the end of a lot of frustration trying to get the bike to run....put some fuel in (and tap in full on position) and she ran sweet from the first kick. I wonder are there issues with these taps? seems unusual to me having had plenty of smaller Honda with similar tap. Anyway, they're not cheap to replace so it will have to come off to see if it can be fixed or else I'll just live with it and carry a small bottle of fuel in my now defunct and empty air box for emergencies...

Looking forward to reading this informative board. Hopefully I can contribute to the resolution of other users' issues and problems from my own experience.

[Ewan 500 K1]

500/4 ....K&N's ... stumpier than others , so no clearance probs. Straight through pipes, mains rejetteed to 110 . Burns fuel like it was still 50p/litre

[singleoverheadbraincell]

Ewan,

That's interesting, I had trouble finding K&N's but I have an alternative which should work well. But I'm concerned about the fuel economy; is that because of the re-jetting? Surely not the more efficient filters? How did you establish exactly which jets are needed?

[matthewmosse]

Standard filter is pretty good. Best alternative I ve found was a k&n that retained the stock mixer chamber and sat next to the battery. Worse fuel economy but better power with loud open pipes. The cone type filters fit but need persuasion, get wet in rain and snow and need re jetting. Personally I ve reached the conclusion that it's fairly hard to improve on millions of yen of research unless you want to alter the focus of the machine - for instance raceing where every second counts and need to economise on fuel isn't an issue.

[LesterPiglet]

Well, it's a 550. You aren't going to break any records. If you do want to, buy a more modern bike. From everything I've read the stock configuration works best. No I'm not willing to experiment as I don't have the time or money. Mine works.

[singleoverheadbraincell]

I'm surprised that fuel economy is adversely affected. I thought it would improve economy, if anything.

I got your email Les, good to hear from you. For some reason the email I sent back to you was returned to me. Anyway, the bike has to be re-registered etc after bringing up from Dublin. I'm in loughinisland, near Seaforde. Sure, we should arrange to meet some time - when I'm road legal.

I'm wondering now what to do about this air filter business. The cone filters were really just an aesthetic consideration.

[LesterPiglet]

You prolly can't reply as you don't have enough posts yet.
Look for a standard airbox. You can stick a K&N in there or something similar but the OEM was designed by Honda and would be hard to improve upon.

[singleoverheadbraincell]

Well the fuel economy will not worry me as long as it is just slightly affected. The cost of the cones is not a concern either (£25). I think the power filters would really complement the bike aesthetically...I know the purist would say the bike was fine originally and probably re-coil at the thought of altering it but there is no accounting for taste.

I don't really relish the thought of fixing the old airbox back on as it is quite tight especially getting the rubbers in. My only real concern is the re-jetting and trying to establish the correct one to use - does anyone know how I can do this??

[SteveD CB500K0]

You will need to do a plug-chop(s) to get the mixture correct.

If you've never heard of it, here's a good start to the research: http://forums.sohc4.net/index.php?topic=92318.0

[Ewan 500 K1]

I got K&Ns from Opie Oils in Cornwall at http://www.opieoils.co.uk/.   Re jet size, just went on advice of a mate that used to race 500's . If anything its running a bit lean on the 110 mains

[Bryanj]

77 K3 Don't do it, itwill never run properly as these were the ones tuned by Honda to meet the US emissions regs and the carbs are totaly different from all the other 500/550 and a swine to get bits for

[LesterPiglet]

The rubbers are a doddle putting back on as long as they are supple. Boil them for a while to soften. Mine are new so were easy. I've had them on and off around 6 times this year and they don't annoy me as much as sorting these friggin taper steering bearings.

[singleoverheadbraincell]

Ok, I get it - enough feedback to put me off the whole idea...........I'll wrestle the airbox back in tomorrow and get a new stock filter. Thanks to all contributors.

Liam