I need the help of some of you expereinced 250r guys. I have an atc 250r wich is stock, except for a plus 3 swing arm and a plus 4 rear axle. Here is what i want. I want to turn this thing into a fast, reliable duner. I want it to be able to shoot hills, but i want to be able to take it through the dunes at dumont and have fun on it. I dont expect it to be the fastest thing out there but i would like it to beat some yfzs.

Here is what i need to know. I have been looking around at big bore kits and ill ive realized is that i dont know what to get. I hear good things about diffrent kits but i dont know which is the best for me. I think i want an esr 330 bolt on kit, I was wondering if i get this then what else do i need to get my trike going, such as, what size carb will i need. What does this kit come with and what kind of power gains will i get. I also dont know what porting to get for all around duning. Any help in making a fast, and good all around duner will be greatly appreciated.

 

what year do you have, water, or air cooled???

 

OH GETTHE ESR KIT THEY LOVE TO WORK ON HONDAS ITS THEIR SPECIALTY MY FIREND HAS THE ESR 330 KIT DAMN ITS FAST. GO FOR THE 330 REALLY GOOD KIT

 

youll need at least a 38mm air stryker that you can order from ESR or a Kehein dealer.


TRX9 porting mid-top end porting is your best bet for duning.

 

dont forget you'll most likely need a esr air box eliminator kit, which requires you to cut your airbox prong off. refer to my pic page for that matter. and a cr intake boot from a 98 cr250. the boot my have to have some rubber removed (mine did) from the potruding point that sits in the cylinder (reed cage). this part needs to be removed until it is flushed depending on what year you get.

also a billet exhuast flange.

 

just like your girl friend told you when she broke up with you bigger is better, go as big as your pocket book will let you 330, 350. the 370 is to much for the 3" over to launch on but it would be fun to dune. i think the 330 bolt on is on its last bore, get the TRX 9 porting if you are going to race the hills. find a decent pipe get a set of 22x11x8 7 or 8 paddle haulers 38 or 39 PWK and you be ready to roll.

 

i have an 85, and what exactly is the airbox eliminator kit, i get that it gets rid of the airbox but wouldnt that just let way to much stuff into your airfilter?

 

thats a subject of debate.

but you would be hard pressed to get the stock intake/airbox boot to fit over the inlet of your 38 or 39 carb. i tried it to no avail, but i believe 344pv has done it. either way, we both run the eliminator kit in the end. keep the filter oiled nicely and dont clean the filter too often is my say. i clean the outwear as much as possible.


I thought about the bolt on 330, but am opting for the 310 instead. that way i always have something to look forward to. [img]i/expressions/face-icon-small-smile.gif[/img]

 

What I did was make my own airbox eliminator kit. I simply got a cone style K&N filter. I measured the opening of my 38mm Keihin, and got a matching filter.

Then, I just bought a piece of bulk radiator hose and a coupler, hooked them together, and voila! No more airbox! I'm also running an Outerwears prefilter. I just zip-tied the assembly to the frame to keep it from flopping around.

Big power increase after rejetting.

 

I run an ESR330. Just remember, the bigger the motor you put in, the more likely you will have bottom end trouble. Broken gears can happen then putting strain on an old set of gears in the sand. If you go with what these guys say, you will need to do some more mods.

For a motor setup, I like the TRX9 porting too. I don't know about CT or other builders, but the ESR works well. If you go with the 330 kit, ESR offers a bolt on kit that fits on your stock cases without machining them out. ESR says you get 3 bores out of the motor. Any bigger and you will have to take apart your bottom end. Either way, you may have to modify your frame to fit the spark plug. I had my frame cut and rewelded to relieve the frame bridge above the spark plug.

You will need to get the carb as they say, but you will need to get a new pipe too. I like the Paul Turner Hi-Rev, but there are other builders with good pipes too.

For your intake, you will need to get a set of reeds, I prefer the Boyessen Rad Valve, but everyone has their preference.

About the carb eliminator kit.........your stock boot will fit on a 39PWK. You will have to melt the plastic and fit it on. What I did is to heat up the outer edge of the boot with a torch (don't melt it or let it catch fire). I then forced a 12oz bottle (beer) into the boot. I let it cool, then heated it up agian with the bottle in the boot for 2-3 times, then fit it on the carb. I removed my airbox too, but went to Home Depot and bought a 4" (I think...I took my boot and matched it) PVC extension for $2. It fits perfectly on the boot and filter. I then attached it with hose clamps. It works perfect.

This stuff will run you about $1500 if you do the labor yourself.

If you want a cheaper option, do this.......port your existing motor $250-400, bore the motor out 100 thousandths (spelling?) which should get your motor to about 265cc $40 and get a wiseco pro-lite pistion $80-100. PT HI-Rev or equivalent $200, 39MM Keihin PWK $200, Rad Valve $150. The gist is this, for another approx $500 you can get the big motor, but I don't know what your budget is. I have the 265 motor in one of my bikes for years now and it runs like a champ. It gets ridden the most, and puts up with it.