K&N filters for flatslides

[Reelinfeele]

Hey all. I need some new filter pods to go with my new flatslides. Should i stick with the single filter per carb or can I go with the double sized filter that fits over 2 carbs? Does the airflow differ? does it matter? 

[SiBag]

Don't think K&N do a pair of double filters that fit the flatties. I intend running velocity stacks and RamAir foam socks on mine.

I think APE do individual filters and I know S&B do individual filters that fit, but not doubles.

[arnout]

I've "always" used the same dual K&N filters (RU-2922[set], RU-2920[single]) listed for the oilcooled GSX-R/GSX-F/Bandit on my Mikuni RS36 and 38 carbs. What flatties are you using?

The intake OD on the RS36/38 is a bit smaller though than that of the CVs (55 vs. 60mm IIRC) but the rubber flange on the dual pods can be snugged up small enough to make it fit..

Alternatively you could have a look at the sizes of available dual filters from K&N on this page and perhaps find a better fit.

Some say foam filter pods are "better" than the cotton gauze type though.. (I've never used foam filters myself, so cannot comment on that..)

 

 

[Gammaboy]

The double filters possibly work better than the singles, but both of them have issues caused by the internal corner and pulses being reflected off the flat end cap of the filter. Mine worked much better when I removed the single Vance & Hines K&N type Pods (which even have an internal bellmouth), and I fitted the Mikuni bellmouths and twin "RamAir" brand slip on foam filters.

[coombehouse]

2 minutes ago, Gammaboy said:

The double filters possibly work better than the singles, but both of them have issues caused by the internal corner and pulses being reflected off the flat end cap of the filter. Mine worked much better when I removed the single Vance & Hines K&N type Pods (which even have an internal bellmouth), and I fitted the Mikuni bellmouths and twin "RamAir" brand slip on foam filters.

Interesting. What were the bad symptoms.

 

[Gammaboy]

It just was better behaved at part throttle, and seemed to fill out a dip in the power delivery. There's also a visible difference in how much the carb rubbers "bounce" at idle.

[coombehouse]

Thanks for that. I have the foam filters on throttle bodies but I will try them on the other bike on rs38s  to see what happens. Will be next year now though as the weather is rubbish.

[KATANAMANGLER]

I have run single K&N pods in the past on my 36s but I now run idividual bellmouths  with twin foam covers. It's alltogether more linear from part throttle to WOT. 

[SiBag]

11 hours ago, arnout said:

I've "always" used the same dual K&N filters (RU-2922[set], RU-2920[single]) listed for the oilcooled GSX-R/GSX-F/Bandit on my Mikuni RS36 and 38 carbs. What flatties are you using?

The intake OD on the RS36/38 is a bit smaller though than that of the CVs (55 vs. 60mm IIRC) but the rubber flange on the dual pods can be snugged up small enough to make it fit..

 

 

 

I honestly thought the 5mm difference in the O/D would have been too much to be taken up by the rubber.

You live and learn, everyday a school day

[KATANAMANGLER]

Actually, when I say bellmouths, I actually use these. They work very well.You just choose the appropriate size to fit your intake and fit foam filters like these over them.

[KATANAMANGLER]

[Hawky]

I would go with the 2-1 ramair filter socks as the other guys have mentioned if running bellmouths 

[Reelinfeele]

19 hours ago, arnout said:

I've "always" used the same dual K&N filters (RU-2922[set], RU-2920[single]) listed for the oilcooled GSX-R/GSX-F/Bandit on my Mikuni RS36 and 38 carbs. What flatties are you using?

The intake OD on the RS36/38 is a bit smaller though than that of the CVs (55 vs. 60mm IIRC) but the rubber flange on the dual pods can be snugged up small enough to make it fit..

Alternatively you could have a look at the sizes of available dual filters from K&N on this page and perhaps find a better fit.

Some say foam filter pods are "better" than the cotton gauze type though.. (I've never used foam filters myself, so cannot comment on that..)

 

 

I have the RS 36's

[Gammaboy]

On 04/11/2016 at 5:28 PM, KATANAMANGLER said:

I have run single K&N pods in the past on my 36s but I now run idividual bellmouths  with twin foam covers. It's alltogether more linear from part throttle to WOT. 

I was honestly amazed at the difference it made - those K&N  singles are so prevalent that you start thinking to yourself "Is it all in my head? Surely all these other fuckers must know something I don't"... when it turns out to be the other way round... I guess a lot of people using them have never had anything else on a flatslide, and just assume that that's how flatties behave.

[KATANAMANGLER]

It was my local dyno guy who told me to ditch them. He said it would give me at least an extra 5bhp and improve the rideability and he would be happy to prove it. He was right.

[Gammaboy]

Must get around to getting my shitbox on a dyno... it's also a lot easier to pull the carbs off with the foam filters.

[Nigkat]

On ‎04‎/‎11‎/‎2016 at 9:21 AM, KATANAMANGLER said:

Actually, when I say bellmouths, I actually use these. They work very well.You just choose the appropriate size to fit your intake and fit foam filters like these over them.

What size hose reducers you using Scott, cant get to my bike to measure. I`ve been using individual k&n`s  but think I`ll give this set up a go.

[KATANAMANGLER]

Can't remember off the top of my head Nigel. I'll take a look and let you know.

[Reelinfeele]

On 11/6/2016 at 6:27 PM, KATANAMANGLER said:

It was my local dyno guy who told me to ditch them. He said it would give me at least an extra 5bhp and improve the rideability and he would be happy to prove it. He was right.

So, I should go with the 50mm bellmouths and the foam covers instead? 

[Gammaboy]

Fuckoath you should.

[Gammaboy]

2 hours ago, Nigkat said:

What size hose reducers you using Scott, cant get to my bike to measure. I`ve been using individual k&n`s  but think I`ll give this set up a go.

If RS mikunis, I guess the ones with the 57mm opening on the small end, and 60mm for the CVs.

[KATANAMANGLER]

Yes I think I went 57 to 70.

[busa ash]

great info guys looking for a set of 38s for an efe motor 

[Reelinfeele]

On 11/4/2016 at 5:21 AM, KATANAMANGLER said:

Actually, when I say bellmouths, I actually use these. They work very well.You just choose the appropriate size to fit your intake and fit foam filters like these over them.

Are these just a 3mm difference from one side to the other? Iam trying to source something like this here in the states. From what I gather the OD on the 36 flats is 54mm. Now, these only need to be 50mm long, correct?

[SiBag]

The length of the bellmouth / velocity stack will effect where the peak power is in the rev range.

As far as I know a short bellmouth / velocity stick will give you HP in the top end, and a longer bellmouth / velocity stack will give you more mid range. (Knowing my luck Iv got this the wrong way around.)