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View Full Version : 250ex'ers, want max HP for cheap? look here!



ryanh250ex
05-31-2006, 01:04 AM
Ok, so like every 250ex owner, i was looking for more power. 4 years ago, I had gotten a T-4 full exhaust, and a jet kit, and over time i made finer tuning adjustments to the carb and added small things to the quad such as Razr rear tires and a UNI air filter (and of course a rejet afterwards) . however, it just wasn't enough.

Now, there are at least a few alternatives to the age-old question "I've done X, Y and Z. How do i go faster?".

I could get the Powroll big-bore kit, but that involves down time to get the cylinder bored and honed by a reputable shop, as well as a good deal of money spent on parts, and if you dont put it together yourself, labor. Not to mention, you'd be left on your last bore.

I could always do a cam, but that again involves tearing into the motor, and of course 150-200 bucks, assuming your core is good. Then there is the downtime that comes along with tearing it apart.

So, i thought. And then i realized. The cheapest mods are always related to the intake and exhaust. I was at the time running a UNI filter, stock snorkel, and no airbox lid. I had recalled seeing a few bikes that run no airbox at all, but used some pod filters. I just bought the UNI, so i didn't feel like spending more money on another filter.

So, i thought again. and came up with another solution.

on my Jeep Grand Cherokee, i made a intake out of Home Depot PVC pipe and rubber Fernco couplers. it worked great. so off i went to Home Depot.

I went and bought a 1 1/4" to 1 1/2" rubber coupler. you'll also need a really tiny clamp for the crankcase breather, try to get one there as well.

Remove the airbox by loosening the clamp at the snorkel and the carb and removing all of those little black tabs holding everything in. dont forget the crankcase tube, which can be a PITA to take-off if you havent done so in a while or at all.

I kept the snorkel tube in place in case i ever need to re-install the airbox back on.

now, from here, go ahead and install the coupler. it's a *little* loose on the 250ex carb, so move the clamp as far on the coupler as you can and make it Bubba tight. Remember, this tube will be subjected to vibrations 24/7, so it's important for it to be extremely tight on the carb.

Now some of yall may not have to do this, but in order for me to get this to work, i had to remove the mesh screen from the UNI filter in order for it to fit on the other end of the coupler. why i dont know, but it wouldnt go on with the mesh cylinder in the filter.

That said, squeeze the boot of the UNI over the boot of the coupler- expect it to be a tight fit. again, make this bubba-tight.

as for the crankcase breather, go to Pep Boys and get one of them cheapo ricer breather vent , clamp it to the tube and you're good to go.

Jetting? i am 100 ft above sealevel, i have a full exhaust and now this setup so i'm running with the needle set one notch below stock, and a 112 main in the stock carb. runs perfect. smooth idle.


Disclaimer: this stuff can kill your bike in the hands of the ignorant. Be careful of where you ride with no airbox.

250ex13
05-31-2006, 01:40 PM
pics?

ryanh250ex
05-31-2006, 01:56 PM
sorry, no pics...i'm back at college in daytona beach FL, 1000 miles from where my quad is.

it's pretty simple though. just a black coupler about 6" long with a UNI filter clamped onto it.

BlasterEaten250
05-31-2006, 02:16 PM
Did you get the new carb working?

ryanh250ex
05-31-2006, 02:52 PM
Originally posted by BlasterEaten250
Did you get the new carb working?

No, i did not, when i went to open the carb up i was surprised to see no pilot jet, no jet needle, and no main. i figured i would probably be lean with the 200X carb and the 112 main i had.

I'll be home again next month, and that will be the beginning of my summer break- so i'll have plenty of time to mess with it then. But for now, it runs great with the stock carb and the way i have it tuned.

BlasterEaten250
05-31-2006, 08:31 PM
Did you get a chance to ride it much? How much power was increased?

ryanh250ex
05-31-2006, 10:23 PM
i only rode for a few minutes- i was getting ready to leave for the airport to catch my flight back to school, and i spent most of that time letting the bike warm up and also setting the idle- i've had some trouble getting the bike to idle correctly as of late due to temperature fluctuations, some carb leak problems (now resolved), etc.

the bike did feel like it had a stronger pull to it and then it could pull better into the upper rpms. because the crankcase breather filter will vent the hot gasses and oil fumes to atmosphere it raises the octane of the gas and keep your intake air temps cooler.

I also noticed an even louder intake note both at idle and part throttle. Maybe it was just my perception of it but at part throttle it seems like the intake was almost as loud as the exhaust..

One thing i am conerned about and wont find out for sure about until the next time i do a major ride on it is how the heat from the header below it will affect the overall temperature of the incoming air. I may throw some heat wrap on both the portion of the header that slips inside the frame rail as well as the black coupler itself.