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Discussion Starter · #1 ·
Hi...are you guys modding your airboxes.....or just removing the cover...

The stock cover has a tiny hole , cannot flow much air at all?

I have a IXIL pipe fitted and K&N , will be ordering the Powertronic if they respond to my emails.

I think the stock airbox is too restrictive.....what are your thoughts....dyno results....seat of the pants, etc....???

thanks
 

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I have thought about this also. Back in the day a common mod to rd250,350, YPVS was to drill holes in the top of the air box. Drill one 50mm hole at a time and try it. If it didn't work or you had one too many holes, you could simply cover them with black duck tape.

Don't know how this would work on a modern computer controlled bike. Would def need the race dynamics piggy back with a map for the extra air.

Think your right, the lid is vey restrictive. As these bikes get older and more common place, you may be able to get a second hand airbox to play with off the bay.
 

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Being able to drill those same holes would be awesome, great way to get some quick gains without spending any coin, or much less than you would have going aftermarket.
 

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Discussion Starter · #5 ·
it is a tiny snorkel....I have a Honda XR650R and the HRC mod is to cut two large holes with riveted screens in the side of the airbox and also rejet of course...... I can't see any performance filter and pipe doing much with that tiny snorkel inlet of an intake

I will be getting the Protronic shortly.....yes using a holesaw drill and the ducktape trick always work.....esp. on dirtbikes or in the rain where you may not any extra moisture getting in
 

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it is a tiny snorkel....I have a Honda XR650R and the HRC mod is to cut two large holes with riveted screens in the side of the airbox and also rejet of course...... I can't see any performance filter and pipe doing much with that tiny snorkel inlet of an intake

I will be getting the Protronic shortly.....yes using a holesaw drill and the ducktape trick always work.....esp. on dirtbikes or in the rain where you may not any extra moisture getting in
Agree....

i had a CRF250M a few bikes back and on the CRF forum the done thing was removing the snorkle, fitting K & N Air filter and drilling the air box lid with 10-15 holes......

Did mine no probs...not sure if it made any speed diference....lol...
 

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it is a tiny snorkel....I have a Honda XR650R and the HRC mod is to cut two large holes with riveted screens in the side of the airbox and also rejet of course...... I can't see any performance filter and pipe doing much with that tiny snorkel inlet of an intake

I will be getting the Protronic shortly.....yes using a holesaw drill and the ducktape trick always work.....esp. on dirtbikes or in the rain where you may not any extra moisture getting in
Agree....

i had a CRF250M a few bikes back and on the CRF forum the done thing was removing the snorkle, fitting K & N Air filter and drilling the air box lid with 10-15 holes......

Did mine no probs...not sure if it made any speed diference....lol...
 

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As Maljohann stated earlier don't modify the airbox and use high flow air filters ( K&N etc ) without a proper remap .
Picture of my open lid airbag with K&N but with a Rapid Bike EVO ( self tuning ) piggyback ECU .
 

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Same with the CRF230,remove inner baffle,snorkel and rejet,but Honda supply the necessary jet so it is a recognised mod,something to do with emissions I believe.
 

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As these bikes are notoriously lean to pass emissions I can't see any advantage to a high flow filter without remapping/controller.
 

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As these bikes are notoriously lean to pass emissions I can't see any advantage to a high flow filter without remapping/controller.
Well someone has to be first out of the trenches.....

had my standard exhaust modified....bit louder, runs ok....

K & N Filter being delivered within the hour (according to Thailand post "track and trace")...

No remap........

Will let you know the results when fitted........
 

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As these bikes are notoriously lean to pass emissions I can't see any advantage to a high flow filter without remapping/controller.
Well someone has to be first out of the trenches .......

The K&N filter arrived....

Opened the air box and tried to pull out the snorkle.....quick investigation saw that the snorkle isn't some little 2" thingy like the CRF - it feeds round towards the back of the bike into a sealed area - gut feeling was this hasn't been done for "tuning" purposes....

Inside the air box is some sort of deflector (see picture 2) - removed that and fitted the new filter (having sprayed some oil on it) - re-assembled everything and went off for a test ride....

When i had the exhaust pipe modified, there was sometimes a bit of popping on de-acceleration - well this has stopped - the bike feels smoother and there is a bit of "induction roar" detectable - was was pretty pleased for such a small outlay....

Anyway back home....

Took seat off and looked at the air box......previously had drilled the CRF air box with good results...

Anyway, i detached the snorkle from the side of the air box, leaving a small gap (see picture 3)...

Re-assembled and went out for a ride.....induction noise louder (which sounded good) , bike felt good and pulled well....

Back home, moved the snorkle so there was a 1/4 inch gap between the snorkle and the air box (see picture 4)....

Re-assembled and off for a ride...

Pretty darn perfect...bike sounds good, pulls well and is smooth...

Equiv of $15 USD well spent in my book....
 

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You can get a 3D printed open airbox lid to free up the airbox a little more, check this thread. I have this open air box lid and although I can't say anything on the increase of top speed, the acceleration and sound are drasticaly improved. i combined this with the Powertronic ECU to adress the lean mixture issue, really happy with it!
 

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As these bikes are notoriously lean to pass emissions I can't see any advantage to a high flow filter without remapping/controller.
if you search on 'DNA filter' on here you will find reports form forum members who found they improved the bike (e.g. smoothed it out a little at low speed) even with no other mods.

Here's one: DNA Filter
 

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Well someone has to be first out of the trenches.....

had my standard exhaust modified....bit louder, runs ok....

K & N Filter being delivered within the hour (according to Thailand post "track and trace")...

No remap........

Will let you know the results when fitted........
You might be the first forum member running that exact combo, but see HERE for another thread detailing air filter and exhaust changes without fueling changes.

If I was you I'd want to know what air/fuel ratio you're now running, I believe you could fairly easily and cheaply achieve that by making yourself an OBD harness and linking to the Torque App

HOW TO MAKE OBD HARNESS
 
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