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Discussion Starter #1 (Edited)
USE THIS INFORMATION AT YOUR OWN RISK

Although not currently listed for the R25/R3 the K&N YA-5008 is as close to the OEM air filter that they offer and they will likely not make one specific for our model because this one is so close.

My non scientific measurements (wasnt far off whats listed on their site)

YA-5008 OEM

Length 5.85" 5.95"
Width 4.36" 4.43"
Flange at rest .486" .490"
Flange compressed .400 .350

A tenth of an inch difference on dimensions is negligible, especially as the opening below the filter is roughly 4.40" x 3.60" so there is lots of sealing overlap.

After a test ride and all I can say for sure is I cant tell a difference other than maybe a change in the drone between 6500-7000, but an air filter 99% of the time wont make any perceivable difference.

20150519_174258.jpg

20150519_174401.jpg
 

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Discussion Starter #2
So after re-evaluating the fitment of this filter, Ive taken it out for now.

OEM filter is a Rigid Plastic Frame
K&N YA5008 is a Rubber Frame

The OEM filter has a positive click/friction when reaching the back of the box. The KN seems to not press against the hold down legs enough for any feedback, and pushing harder bends the filter up (could be an issue if the lid were installed improperly).

I think I might find some thin shim material and build a frame for the top of the KN filter to not only help the positive seal at the front/ and rear (which is the only place the filter is held in) but to support the whole filter and resist the middle bending up.

Could just be because the rubber is so soft you cant tell there is a pressure being applied, but because OEM has a rigid sealing frame... Ill make one for my K&N!
 

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So after re-evaluating the fitment of this filter, Ive taken it out for now.

OEM filter is a Rigid Plastic Frame
K&N YA5008 is a Rubber Frame

The OEM filter has a positive click/friction when reaching the back of the box. The KN seems to not press against the hold down legs enough for any feedback, and pushing harder bends the filter up (could be an issue if the lid were installed improperly).

I think I might find some thin shim material and build a frame for the top of the KN filter to not only help the positive seal at the front/ and rear (which is the only place the filter is held in) but to support the whole filter and resist the middle bending up.

Could just be because the rubber is so soft you cant tell there is a pressure being applied, but because OEM has a rigid sealing frame... Ill make one for my K&N!
do you think using a thin aluminum along with foam neatly RTV to the new filter will help wih the gap or if you can remove the shim from the old filter and modify it to the new filter to get the fit that you want perhaps?
 

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MAV can you post a picture of the filter installed in the motorcycle so we can get a clear understanding of the current fit and finish of the new filter. As long as the filter covers the throttle body holes then I think we are in business small adjustments can be made with ease to get that perfect fit.
 

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Definitely only use K&N filters at your own risk!

The last two K&N filters I installed on two different bikes didn't fit correctly.

I bought the exact filter specified for each bike, a Kawasaki VN800E and a Kawasaki Mean Streak, and the diameter of both filters was larger than the stock ones, which meant that there ended being a small gap between the filter and the housing that let dirt be pulled straight into the engine.

I could actually see a dirty streak mark on the housings where the gap was and there was crud inside the filter at that point.

The service manager at my local dealership said their mechanics see this all the time and have seen cylinder wall damage because of it. They do not recommend using K&N filters for this reason.
 

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Discussion Starter #6
MAV can you post a picture of the filter installed in the motorcycle so we can get a clear understanding of the current fit and finish of the new filter. As long as the filter covers the throttle body holes then I think we are in business small adjustments can be made with ease to get that perfect fit.
After finding 20mins to get out there and check it out further Ive concluded this.

The KN filter has a rubber sealing edge vs the OEM Foam seal. If you look back at my measurements, the OEM is more compressible than the KN and this is where the issue arises.

At the back of the Airbox is the lip that catches the filter and there is a raised edge on it that pushes down on the filter frame to help compress the seal
rear box.jpg

When the OEM filter is installed there is a small portion of the air box showing
oem seat.jpg

When the KN filter is installed the edge of the filter is flush with the end of the box. Now being the KN is .100" shorter and is not leaving any visible edge when installed, it means the KN is just barely catching the edge at the back of the box but not sliding under.
knseat.jpg
Basically... The KN filter sealing edge is too stiff to compress under this raised lip at the back of the box and in turn any force applied to the front of the filter bends it upwards in the middle because of the rubber frame design.

I tried for a good 5 mins to try and get the KN to seat under the lip at the rear of the box pushing/rocking/stuffed my hand in as far as possible and had no luck

So all you can do is shave the frame of the KN to get it to slide under. But then you open a whole can of potential issues if you dont do it perfectly.

To be 100% honest... it boils down to an Airbox DESIGNED for a rigid frame filter w/foam seal and not a rubber frame one as it only supports the filter in place at the ends of the filter and not down the sides. Even if you shave the end of the KN to fit under the lip at the rear you still have the real potential of the middle of the filter bending up and letting debris by. This goes hand in hand with the lack of compressibility of the KN seal.

Personally Im running with stock for now... IF I find some free Garage time Ill fool around with the KN and see about retrofitting it to work properly, maybe putting a foam sealing edge and cutting off the hard rubber KN sealing edge and refining my frame I made of .020 steel banding, which would work great for pushing down on the middle of the filter if there was room for it and the filter under that ledge in the back of the box.

Who knows, maybe I got a filter that came out thicker than normal and if someone else were to buy one it would slip right in. I still wouldnt trust the sealing in the center of the filter like FangShui said he had experienced.

The BMC FM528/20 filter appears to have a foam seal but I think is still a rubber frame but would probably require less (maybe no) out of the box tweaking to get it to work.
 

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Well Mav you tried to make it work. Good inforation for though also
 

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FWIW I personally like the innovation and features of the Dutch company MWR Airfilters (used by many well known racing teams, especially in Europe). However, they are more expensive than your usual OEM, K&N, etc.

They have two models for the R25/R3, one for OEM replacement and one for racing only (requires ECU flash or fuel controller):
http://mwrairfilters.us/prodDetail.asp?ID=4114
http://mwrairfilters.us/prodDetail.asp?ID=4115
Looks good and it's not that pricey when you consider it's a lifetime filter.

The mechanics at my local dealership don't like K&N filters AT ALL. They have told me that they see a LOT of bikes come through with K&Ns where there isn't a good seal and dirt and grit have gotten past the filter seal and caused damage to the engine. It's job security for them, though!

I had a K&N on my Kawasaki Drifter years ago and the fit wasn't good at all. It was the one specified by K&N but was slightly too large for the air box and the seal had a bulge in it when installed, with a small gap. I could visibly see where dirt had gone right through there, bypassing the filter. I think there are problems with K&N sizing as manufactured....
 

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I don't think K&N test fits their drop in filters at all. I had the same overly thick rubber seal on a filter for my car. It was impossible to close the air box filter with the K&N. Not even close. It's like someone hands the designer a stock filter and he just copies it's shape, then hands the guy back a k&N with roughly the same dimensions.
 

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Discussion Starter #12
FWIW I personally like the innovation and features of the Dutch company MWR Airfilters (used by many well known racing teams, especially in Europe). However, they are more expensive than your usual OEM, K&N, etc.

They have two models for the R25/R3, one for OEM replacement and one for racing only (requires ECU flash or fuel controller):
http://mwrairfilters.us/prodDetail.asp?ID=4114
http://mwrairfilters.us/prodDetail.asp?ID=4115
Thanks for the links... Im liking the foam seal with a rigid frame design... this could be the one to go for if the BMC filter doesnt work out.

To those looking at the link, the main picture is not the actual filter... you must look at the 'Installed' filter pictures which clearly show the rigid plastic frame like on the OEM Yammy filter
 

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Although not currently listed for the R25/R3 the K&N YA-5008 is as close to the OEM air filter that they offer and they will likely not make one specific for our model because this one is so close.
Just curious - have you spoken to someone at K&N to verify this?
 

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Discussion Starter #14
Just curious - have you spoken to someone at K&N to verify this?
Personally no, all based on assumption.

This was all back fresh upon release before anyone but R&G racing was listing an aftermarket filter for the R25/R3.

R&G had listed the BMC filter that is now referenced on BMC's website for the R3. I used the other fitment models (SR400 bike, TMax Scooter) listed and crossed it to what K&N was listing for those particular models.

K&N does have the R3 listed on their website now, but nothing is listed for fitting it. Who knows, maybe they will manufacture a filter specific for it, but I personally wouldn't keep my hopes up.
 

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I had the same problem with the K&N I placed on my ninja300. The rubber frame design made it hard to fit into the airbox and I had to jam it in to make it work. I didn't have any problems with the filter though.
 

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Discussion Starter #17
Just installed my Yamaha OE Performance filter. It is superior to the KN mentioned in this thread and I highly recommend it.

As you can see from the photos the Performance filter reaches under the lip at the back of the box with a positive friction feel when installing.
Yam Filter.jpg

This is because of the slightly thinner frame and much softer rubber sealing edge.
Yam KN filter.jpg

In my opinion stick with the Yamaha OE Performance filter over the KN mentioned in this thread and you'll be very happy.
 

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That's good info, I wasn't too sure about that K&N not fitting very well. The BMC race filter fits well and has a foam gasket that fills the extra space so it also gives a nice positive feel and a good fit. I'm happy with it.
Jesse
 

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Definitely, agree.
Why not just go with the BMC.

It's specifically made for the R3.

BMC has a long proven track record of high quality filters.


Probably easiest quickest mod you can do to the R3.





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But the air filter does not come with a cleaner like kn air filters do. I'm just worried if I use regular soap and water it can damage the filter.
 
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