forced air on 250

[Rider-trx_250ex]

What do you think of custom making a tube that goes to the front of the quad with a screen at the opening so nothing gets in the airbox out of sheet aluminum, so that air will be forced into the airbox, not pulled in?

[ryanh250ex]

you'd need more than a screen to keep junk out.

anyhow, i run no airbox (no lid, no airbox, a crankcase breather vent, etc) on my 250ex, and i'm probably the only one to do so.

at times i have wondered if maybe you had scoops (those flat rectangular exhaust tips you sometimes see on cars and some trucks would be a good start) somehow connected to the bottom of the front fender at least on the left side (so it doesn't interfere and get heated up from the headpipe. perhaps delete the airbox and just run a short tube like iam so i can the filter designed for the 250ex airbox to the carb. perhaps take a outerwears unit and cut a hole in it the size of the tube. then use some sort of adhesive to glue the edge of the tube to the hole in the outerwears. use PVC pipe coated in heatwrap to run from the front fender, to just under the fuel line, right into the filter.

ram air does in fact work, but it will never generate boost (albeit it will show positive pressure) at the speeds we are talking about here. you'll see a gain, but dont expect it to be there if you trail ride.

another way to get performance the cheap is a bigger carb. i have a 200x carb that i've been meaning to put on for months, i just havent been home long enough to mess with it. the intake manfiold for both the ATC200x and the 250ex look to be identical. i think a 26mm XR200 carb will work as well

[Rider-trx_250ex]

"perhaps delete the airbox and just run a short tube like iam so i can the filter designed for the 250ex airbox to the carb. perhaps take a outerwears unit and cut a hole in it the size of the tube. then use some sort of adhesive to glue the edge of the tube to the hole in the outerwears. use PVC pipe coated in heatwrap to run from the front fender, to just under the fuel line, right into the filter."

I'm lost starting with that. lol Can you maybe post a pic of what you mean?

[ryanh250ex]

Originally posted by Rider-trx_250ex
"perhaps delete the airbox and just run a short tube like iam so i can the filter designed for the 250ex airbox to the carb. perhaps take a outerwears unit and cut a hole in it the size of the tube. then use some sort of adhesive to glue the edge of the tube to the hole in the outerwears. use PVC pipe coated in heatwrap to run from the front fender, to just under the fuel line, right into the filter."

I'm lost starting with that. lol Can you maybe post a pic of what you mean?


OK this is really not all that hard bro

1. delete airbox= throw it out or whatever, junk it
2. go to home depot and buy a rubber coupler . the size is 1.25 to 1.5". PVC pipe (white plastic piping) should be in the same section...buy whatever size you want....bigger pipe will flow more but at a slower speed than smaller piping...and obviously bigger piping will be tougher to fit
3. mount the smaller end of the coupler to the carb, and put the air filter on the big end of the coupler
4. buy an outerwears if you haven't already
5. wherever you want the air to ram into the outerwares, cut a hole in it. the size of the hole should be approximately the size of the tube that will be ramming the air into the filter
6. glue the edge of tube so that it is flush with the hole you just cut out in the outerwares
7. route the PVC pipe so that it doesn't get in the way of your legs when riding. i would zip tie it to the frame rails or something. wrap it in heat wrap so it doesn't get hot from the engine

[Rider-trx_250ex]

Originally posted by ryanh250ex
OK this is really not all that hard bro

1. delete airbox= throw it out or whatever, junk it
2. go to home depot and buy a rubber coupler . the size is 1.25 to 1.5". PVC pipe (white plastic piping) should be in the same section...buy whatever size you want....bigger pipe will flow more but at a slower speed than smaller piping...and obviously bigger piping will be tougher to fit
3. mount the smaller end of the coupler to the carb, and put the air filter on the big end of the coupler
4. buy an outerwears if you haven't already
5. wherever you want the air to ram into the outerwares, cut a hole in it. the size of the hole should be approximately the size of the tube that will be ramming the air into the filter
6. glue the edge of tube so that it is flush with the hole you just cut out in the outerwares
7. route the PVC pipe so that it doesn't get in the way of your legs when riding. i would zip tie it to the frame rails or something. wrap it in heat wrap so it doesn't get hot from the engine

i understood most of that but ur wording was all messed up, thats waht confused me

[ryanh250ex]

Originally posted by Rider-trx_250ex
i understood most of that but ur wording was all messed up, thats waht confused me

no worries

boy you should be thankin' your lucky stars, when i was writing my posts earlier i had a old old old post at ATV Connection in mind, and by the Grace of God i actually found it again :eek2:


credit to Trx250Rob
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The only practicle way to boost your air intake pressure without a turbo is to build a ram-air. I experimented with this about 19 years ago on an ATC 185s.

Here is what I did:

First you seal off all the openings on the airbox to make it air tight, I used alot of ducttape.

I then cut a 3 inch hole on the side of the airbox and attached a PVC tube (3 inch OD)out of the side of the using JB weld. Of course I sealed of the original intake opening, which I couldn't use because of the angle, size and position.

Next, I attached a 3 inch ID hose (fish tank hose)to the PVC pipe sticking out of the airbox. I used muffler straps to secure the hose up toward the side of the gas tank. Then I placed a funnel at the end of the hose, held in place by wires. I looked awful and I couldn't use the rear fenders during the test.

The results: Increadibly enough, the bike picked up some pep in the lowend. At the time I did expect this but as it turns out a long intake track is benificial to low end power. It feel quite snappy on the bottom end compared to the airboxless, unifilter setup I normally ran.

As for the results, we timed my bike through 10 runs each with this contration and then without. All test were done without the rear fenders so there would be no aerodynamical advantage.

Well we have a strip of pavement we used to drag on. If was somewhere between 1/8 and 1/4 mile long. After everything was said and done the ram-air assited runs were about 1 second faster than the open airfilter runs.

We also had a street bike run along to get a Max MPH and accoring to the bike speedo we picked up between 2-4 MPH with the ram-air.

As for how the bike felt, usually it settled into 5 gear is about 3 seconds and then stopped reving. With the ram-air once the 185s hit the top of 4 gear it felt like it got its second wind and 5th seaming to pull a lot longer about 6 seconds before it topped out. It also go very loud and punchy pulling 5 gear wheelies with ease.

Also the jetting was perfect with the open air-filter and just slightly lean when the ram was used.

Well that's my story. The mod was a success but not practicle because you had to be going about 60 MPH so it could work, if you used it off-road your filter and airbox would be a mess and it looked, like a rig.

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