going to a bigger carb, how will this affect how i jet the bike?

[ryanh250ex]

OK, i'm going where very few have gone before, by going with a big(ger) carb on my 250ex. yeah yeah yeah, i know, buy a 400/450..........save it. :rolleyes:


anyways, i have a full exhaust (T-4, no end cap, no quiet core), UNI filter, no airbox lid. i'm running a 112 main right now, which is a little big- right now the bike has no spark arrestor, and that leaned it out a little bit to where its only slightly rich now but being that i ride in the woods, i dont think i'm going to run long-term with no arrestor.

the stock carb is 22mm, deathman53 gave me a 24mm keihin carb off of a ATC200X. not a huge jump, i know, but you can't beat free.

so anyhow, the 200X carb has a 120 main (K&N/Keihin) jet right now. given the 2mm bump in throat size of the carb, what should i expect to do in terms of rejetting this thing? slightly larger than current? much larger?

FWIW i will not be running an airbox either, most likely a 250ex UNI filter coupled right to the carb with perhaps some cut-up pantyhose as a prefilter.

[hybrid_hatch]

Iam in the process as we speak of putting a 300ex carb on my 06 250ex..I was going to post a how-to..but..to many people are haters and say "get a 400ex" or a new bike..I already have the 300ex intake boot mounted to the 250ex head and the carb will be here tomorrow along with the dynojet kit..so far the hard part seems to be the carb to airbox connection..once I tune it in I will let you know what I had to do..BTW I will be using a wideband o2 to set this up..


FYI..

the 06 recon 250 (TRX250TM) has a 32mm carb stock with the same engine as the 250ex..

http://powersports.honda.com/atvs/utility/model.asp?ModelName=FourTrax+Recon&ModelYear=2006&ModelId=TRX250TM6

dont put the filter right on the carb it will backfire and catch the filter on fire!!!!


i did it with my suzuki dirtbike and it caught fire ALOT

[Sjorge450R]

Originally posted by 89honda 250x
dont put the filter right on the carb it will backfire and catch the filter on fire!!!!


i did it with my suzuki dirtbike and it caught fire ALOT

thats cause you didnt do something wrong. I races 90's for a year and thats all we used was POD filters. I even have one on my trike and nothing has happened.

[ryanh250ex]

Originally posted by 89honda 250x
dont put the filter right on the carb it will backfire and catch the filter on fire!!!!


i did it with my suzuki dirtbike and it caught fire ALOT

i am suspect of your level of technical knowledge seeing as you store GASOLINE overflow in a PLASTIC water bottle in close contact with your motor :rolleyes:

i've used pod filters before, i had a '84 Z50 that i built from the ground up, it used a Uni clamp-on filter. no problems except for a need to clean and re-oil the air filter regularly.

hybrid, thats awesome that you're taking on the project of using a 300ex carb- i was originally going to attempt doing that, but IIRC the 300ex carb mounts up totally different than the 250ex does... I unfortunately am stuck at college in FL (i live in NJ) for the time being so i havent had any time to mess with the carb, but the reason why I acquired the 200X carb is that it mounts up exactly the same as a 250ex, and it looks to be 100% bolt-on, no hassle, no worries...

I'm very surprised that they made a huge jump in carburetor size on the Recon. they didn't do it on the 250ex, either. Is it possible that this is a typo?

Since the ATC carb was a freebie, the next step will be to mount either a 27mm aftermarket carb, or a 26mm carb off of a XR200 dirtbike. i think if the 300ex carb could be easily swapped, that would be the way to go, but my whole reason for a swap is cheap and easy to install performance. a decent XR200 carb will no doubt be cheaper than a 300ex carb.

hybrid do you have any pics of your carb swap?

i had a 1982 suzuki dr500 and the guy at the shop told me to put it right onto the carb and it would backfire or something when i would crank it and catch fire

[hybrid_hatch]

this is the head after I drilled and tapped a new mounting hole for the 300ex mani (boot) and you can see the paint mark of what needed to be removed (porting) to make it flow..

http://highboostracing.com/mis/quad_head_300excarb%20002.jpg

this is the head with the new manifold on and porting done..

http://highboostracing.com/mis/quad_head_300excarb%20003.jpg

this is a side shot to see how far off the 300 bolt hole is from the 250..

http://highboostracing.com/mis/quad_head_300excarb%20004.jpg

BTW..

this quad is less than 2 weeks old! only got it after my yfz450 was ripped off and the wife wanted something she could ride..so might aswell makw it fast enough for both of us..

[ryanh250ex]

Originally posted by hybrid_hatch
this is the head after I drilled and tapped a new mounting hole for the 300ex mani (boot) and you can see the paint mark of what needed to be removed (porting) to make it flow..

http://highboostracing.com/mis/quad_head_300excarb%20002.jpg

this is the head with the new manifold on and porting done..

http://highboostracing.com/mis/quad_head_300excarb%20003.jpg

this is a side shot to see how far off the 300 bolt hole is from the 250..

http://highboostracing.com/mis/quad_head_300excarb%20004.jpg

BTW..

this quad is less than 2 weeks old! only got it after my yfz450 was ripped off and the wife wanted something she could ride..so might aswell makw it fast enough for both of us..


Hybrid,

I must say, major props to you for making something like this work for you.

exactly how hard is pulling the head? I have a shop manual, but it's currently 1000 miles away from me.

how did you do the porting of the intake manifold? dremel? that's a good bit of material to hack off...


what other mods are you planning or have done already? i am betting a 32mm carb and ported intake manifold (have you ported the head as well?) will make the bike very top-end oriented.

thats a bit more work that i wanted to do just to bolt a carb on- DIY fabrication is really cool but my goal was to swap on something that is bolt-on and go, but you sure have alot more stones than i do. Let us know how it goes....

-Ryan

[hybrid_hatch]

I build race engines for honda 4 cylinders.. (civic,integra,prelude) and have full porting tools..there is really not that much to do to make it work..drill/tap 1 bolt hole and remove a little meat around the intake port.

I have this head fully ported with a 33mm intake valve (valve is out of a B18C1 acura gsr head that has been machined down at the end for correct stem height (same 5.5mm shank for the 250ex and honda B series VTEC heads) with custom rocket motorsports springs and retainers going in..piston is a CP 12.0-1 custom piston with a custom sleeve..

like I said..I have not owned this bike long and will get more done as time goes on..I have next to nothing into this bike cash wise as I have a bunch of automotive parts laying around which I can mod to fit this app..I mod this bike because I can and because my wife needs the auto clutch..if my yfz450 didnt get ripped I may have never of modded this quad..but hey..who are we if we dont push the limits and see what we can do..I should be able to hit 60/63 mph when done with all the mods..most say it cant be done due to shaft drive..but..what they dont understand is if you raise the rev limit and have enough power to pull to rev limit you will go faster!

[BlasterEaten250]

That is awesome that you guys are modding the 250.

When one of you are done, it would be cool to see a thread how to do it in the how-to section. Mods delete any post that doesnt have to do with the topic (like if someone said "go buy a 400")

I can't wait to see what it is like when it's done:p

[ryanh250ex]

Originally posted by hybrid_hatch
I build race engines for honda 4 cylinders.. (civic,integra,prelude) and have full porting tools..there is really not that much to do to make it work..drill/tap 1 bolt hole and remove a little meat around the intake port.

I have this head fully ported with a 33mm intake valve (valve is out of a B18C1 acura gsr head that has been machined down at the end for correct stem height (same 5.5mm shank for the 250ex and honda B series VTEC heads) with custom rocket motorsports springs and retainers going in..piston is a CP 12.0-1 custom piston with a custom sleeve..

like I said..I have not owned this bike long and will get more done as time goes on..I have next to nothing into this bike cash wise as I have a bunch of automotive parts laying around which I can mod to fit this app..I mod this bike because I can and because my wife needs the auto clutch..if my yfz450 didnt get ripped I may have never of modded this quad..but hey..who are we if we dont push the limits and see what we can do..I should be able to hit 60/63 mph when done with all the mods..most say it cant be done due to shaft drive..but..what they dont understand is if you raise the rev limit and have enough power to pull to rev limit you will go faster!



:eek2: :eek: :eek: :eek: :eek2:

hybrid, that is INSANE!!!

what are you going to do about pushrods and the cam? also, approx what displacement will the custom sleeve be?

by all means, let us know how it turns out...

[hybrid_hatch]

it will be 267cc's when done..

push rods are stock at the moment but will be checking into some V8 chevy push rods at the local speed shop..cam will be a custom rocket motorsports cam or a web cam..

[hybrid_hatch]

ok heres where iam at right now..

I ghetto'ed the airbox to use the stock filter and it seems to work damn good..I had to jet up like crazy!!

stock slow jet (pilot) is a 38
stock main jet is a 122

I had to put in a 40 slow jet and a dynojet 124 and the fuel screw is at 2 1/4 out..I did all my tuning with a tech edge wideband o2 and backed up the results with plug readings and uphill pulls at diff throttle ranges..

also needle is at 4th clip down..

Iam now at 13.8 a/f at idle and high 12's to low 13's on air fuel from 1/4 throttle on..

FYI..this is still at stock bore/stroke and compression..thing pulls like no other to my 9500 redline.(big gun rev box)

[ryanh250ex]

Originally posted by hybrid_hatch
ok heres where iam at right now..

I ghetto'ed the airbox to use the stock filter and it seems to work damn good..I had to jet up like crazy!!

stock slow jet (pilot) is a 38
stock main jet is a 122

I had to put in a 40 slow jet and a dynojet 124 and the fuel screw is at 2 1/4 out..I did all my tuning with a tech edge wideband o2 and backed up the results with plug readings and uphill pulls at diff throttle ranges..

also needle is at 4th clip down..

Iam now at 13.8 a/f at idle and high 12's to low 13's on air fuel from 1/4 throttle on..

FYI..this is still at stock bore/stroke and compression..thing pulls like no other to my 9500 redline.(big gun rev box)


wow, i'm pressed that you were able to use the 32mm carb with the stock displacement/compression.

does the bike still maintain good lowend and midrange, and keeps pulling harder as the rpms increase?

what are you running in terms of exhaust?

these runs you made are with the head fully ported w/ the 33mm intake valve, the 300ex intake/boot, 300ex carb, with the 250ex airbox and stock air filter (lid off or on??)

i'd personally love to see its performance via a video or two...

Keep us updated...

-Ryan

[hybrid_hatch]

ported head,over sized valve,300ex carb,boot,stock air box no lid with stock filter with the metal drum inside removed.

exhaust is a HMF..and it has to much lowend still..I thought the bigger carb would make it lose lowend but it didnt..