K&N Airfilter

[Blapper]

I changed my air filter today for one of those air filters for life jobbies from K&N.

The job couldn't be simpler, but the bike has changed subtly now. There is more induction noise which is not particularly nice. The noise seems to come from the fact that the original has a 'tuned port' like a reflex loudspeaker which has a certain diameter and length to its tube whereas the K&N jobbie just has a whacking great hole with no tube. I wonder whether this is designed to act as a system and the slug of air cleverly designed to be quiet and to give best performance because I now have a slight flat-spot as I first open the throttle and the bike starts to accelerate.

Has anybody else fitted one of these and noticed a/ the noise, and b/ the slight hesitation? :confused:

[Blapper]

Update: Looks like the flat spot was just the motor wasn't warmed up but the noise is still there and just as bad. It reminds me of kids thrashing clapped out cars with the air filter removed. Yuk.

[garynortheast]

I've had a K&N air filter on my curvy since I bought it more than six years ago. I must say I've never noticed the noise or any performance issues. I do like the fact that I can just clean it, re-oil it and pop it back in.

[Blapper]

Hi Gary, Yes, I like the lifetime air filter idea, and like I said in the update above, the performance issue was when I took it for a quick blast around the block, the motor wasn't warm enough and the flat spot was just because of that.

I just got back from a ride to Southend and back and the performance is fine, but the design of the inside of the air filter lacks the aerodynamic tweaks of the original so it is noisy at low to mid revs which is where I ride mostly. You have not noticed this with yours then? Did you fit yours? If so, did you notice the K&N has a big basic hole in it?

[garynortheast]

It was already fitted when I bought the bike Blapper, so I've never had anything to compare it with. I wear earplugs all the time when I'm riding too although when I've had the engine running and not had earplugs in I've never really thought the induction noise to be particularly excessive.
Put up a picture of your bike with the tank lifted and the air filter fitted so I can see it.

[Blapper]

That's good info thanks Seeker.

Gary: I rode with plugs in yesterday (as the crutch rocket position makes for too much wind noise even with a Fabri double bubble) and couldn't believe how it made the bike sound - dramatically more transmission whine. Enough that I pulled over and checked my chain tension in case it had changed and was ripping my mainshaft bearings out!

[Blapper]

I'm thinking I will cut the top off the old one and screw it to the K&N !!!!

[garynortheast]

The K&N has a top on it as an integral part as I recall. That's what should screw down onto the airbox.

[Blapper]

You are right Gary, the top does screw down on the air filter. What I am describing is the hole which allows air into the filter that is just a basic big hole on the K&N but a 'tuned port' on the Suzuki part.

I have cut the port off the old air filter along with removing the dimple from the bottom using different sized hole saws and bonded/screwed them onto the K&N. The result is that I now have a nice quiet lifetime air filter.

Reezult.

[johnnyrod]

Blimey mate just take it off if you don't like it that much! It should flow more air so you can get leanness, mainly at the top end, which means some upjetting but you really need a dyno to do that job right. The earliest ones were rubbish but they sorted that out a long time ago. Yes there is more induction noise but I'd hardly call it offensive, but then it's loudest when I've got my head almost on the tank and the rev needle in peak power territory.

[Blapper]

Hi Johnnyrod.

I think our motivations are different. I like a quiet bike these days (except for a small uplift on the exhaust noise to help wake up car drivers). I just fitted the K&N because the previous owner gave it to me with the bike and I like the idea of a washable filter. Stock motor is fine for me, I don't need to fiddle with it for more power, I just want to ride it. I'm happy with it now, it's as quiet as stock, but washable which is pension friendly.