Honda-SOHC

SOHC.co.uk Forums => CB650 => Topic started by: Ken4004 on May 09, 2026, 02:25:07 PM

Title: Air filter for cb400 f
Post by: Ken4004 on May 09, 2026, 02:25:07 PM

HI everyone

Just thinking about the future as I have fitted a new standard air filter on my cb400 F , has anyone fitted a K and N reusable filter to their bike and if so have there been any issues ?

I used one on my 1977 Z1000 and it seemed OK just wondered what people views were !

Title: Re: Air filter for cb400 f
Post by: McCabe-Thiele (Ted) on May 09, 2026, 03:21:58 PM

I've used K&N air filters previously on several cars, they claimed better performance.

Not sure if the K&N filter on a bike would affect the fuel  mixture adversly, especially on a smaller engine.

Title: Re: Air filter for cb400 f
Post by: Bryanj on May 09, 2026, 11:08:26 PM

There have been several adverse reports on the US forum

Title: Re: Air filter for cb400 f
Post by: Ken4004 on May 10, 2026, 06:06:47 AM

Hi Bryan

Yes I did see those , showing dirt getting past the filter and on some cases even evidence of the pistons and bore of some bikes getting scored so probably worth avoiding and stick to what you know !

Title: Re: Air filter for cb400 f
Post by: Laverda Dave on May 10, 2026, 02:04:06 PM

I assume the installer of the K&N filters used the filter oil and didn't install them dry?

Title: Re: Air filter for cb400 f
Post by: Bryanj on May 10, 2026, 03:16:08 PM

Aparently oiling them makes the mixture control go bad

Title: Re: Air filter for cb400 f
Post by: Athame57 on May 11, 2026, 07:24:54 AM

There is actually a youtube video on this matter.
https://youtu.be/PSMxWjxE1bw?si=zYX7NTobfcj7tOre

Title: Re: Air filter for cb400 f
Post by: Laverda Dave on May 11, 2026, 08:59:54 AM

Back in the day when I used to race a bit of speedway my least favourite job was cleaning and re-oiling the K&N filter after every meeting. Back in the 80’s the filter used to poke out in the open on the right hand side of the bike. The filter used to get filthy with dust and shale and especially after a tumble! Thankfully they are centrally located now and protected by the bike covers. If you ran the filter dry it was a very quick way to scrap a motor🫩
K&N filter oil was expensive back then and probably still is!