250X carb VS 300EX carb

[1987TRX250X]

I'd like to know if the carb on a 300EX is bigger than the on a 250X. :confused:

I know the carb on a 400EX is bigger than the one on my 250X and that it fits on it, but since I mainly do fast trail riding (my bike is setup a little like a XC quad), I'm scared that if I fit one from a 400EX, I will loose bottom and a little midrange power. That why I'd like to fit on from a 300EX if it is bigger.

:ermm: By the way, what are carb size for
- 250X
- 300EX
- 400EX

So if the 300EX carb is bigger than the 250X one, I'd be interested to buy a 300EX carb if somebody has one for sale cheap!!! :)

Thanks

[jiggaman2401]

I believe they are the same size same exact engine for that matter.. The only difference between them is the 250x is a kick start 300ex electric start..

[YZ400EX]

The 300 has a shorter stroke than the 250, but as for the carbs they are the exact same..no difference at all..

[BigDaddyCMU]

Isn't it the other way around with the strokes? I believe that's why the 300 motor has more displacement - it has a longer stroke.

[YZ400EX]

I may be a little mixed up with my previous statement..cant rememeber fully, but I know the carbs are identical..

[dirtmomma]

IDK BUT if you need a stock 300 carb I have one for 75 + ship :D also have a Dynajet kit too for $30

As for the 400 carb & woods riding, it's not really a problem once Iput mine on it was WAYYYYY better & I didn't loose any bottom end either :) Good Luck LMK if ya need the carb!!

[John250X]

Yea I put a 400ex carb on my 250x and had it jetted and took the choke off and I can beat a 300ex off the line if anything I gained more bottom end.

[1987TRX250X]

Originally posted by John250X
Yea I put a 400ex carb on my 250x and had it jetted and took the choke off and I can beat a 300ex off the line if anything I gained more bottom end.

Why did you take off the choke? It wouldn't fit? Did you change the rubber boot between the airbox and the carb? Or the one between the carb and the cylinder head? Did you have to midify anything else to fit the carb?

Did you have to jet leaner or richer? Leaner probably...

How much for a good used 400ex carb?

I'm in Québec

Thanks for your help everybody!

:)

[John250X]

Actualy I got mine on Ebay for 35 The guy had taken the choke off. I had my friend mechanic rejet it for me. He had to jet it leaner. It fit fine on the intake boot but we took a dremal and had to ream the hole out on the air box boot. Still having a little bit of trouble with it fitting. He told me I should just buy a air filter the connects right to the carb.I might try that

[John250X]

I was told that taking the choke off gives the carb better air flow. I haven't yet had a problem starting it and All I know it with that carb and my exaust I can bet a 300ex with exaust.

[dirtmomma]

As far as the "boots" I used my stock 300 boot, I just boiled some water then stuck the ends in the water & once it ws hot put it on the carb, it worked GREAT!!! It did pop off the carb a couple times but we put some Motoseal on it & it hasn't popped off again :D As for jetting I'm running a 150 main @ 500' level

[ghak99]

Originally posted by dirtmomma
As far as the "boots" I used my stock 300 boot, I just boiled some water then stuck the ends in the water & once it ws hot put it on the carb, it worked GREAT!!! It did pop off the carb a couple times but we put some Motoseal on it & it hasn't popped off again :D As for jetting I'm running a 150 main @ 500' level

Glad to hear it worked out good for you.;)



It seems like I have not been on here in a long time. For those of you wanting to do the switch, I feel it is a very easy and cheap mod. You can normally pick up a 400ex carb for around 50 or less if you are lucky. I went ahead and used a 350x air boot to give it a little more air and a slightly better fit. After I get a bigger head, I will probably go with the air filter right to the carb as you stated above, only because it will no longer see any trails.

[dirtmomma]

Originally posted by ghak99
Glad to hear it worked out good for you.;)



It seems like I have not been on here in a long time. For those of you wanting to do the switch, I feel it is a very easy and cheap mod. You can normally pick up a 400ex carb for around 50 or less if you are lucky. I went ahead and used a 350x air boot to give it a little more air and a slightly better fit. After I get a bigger head, I will probably go with the air filter right to the carb as you stated above, only because it will no longer see any trails.

NO you haven't been on in awhile Gee you must have a life ;) yep it worked out just fine & still is :)

Originally posted by dirtmomma
IDK BUT if you need a stock 300 carb I have one for 75 + ship :D also have a Dynajet kit too for $30

As for the 400 carb & woods riding, it's not really a problem once Iput mine on it was WAYYYYY better & I didn't loose any bottom end either :) Good Luck LMK if ya need the carb!!

75 for a stock 300 carb? keep dreaming..you could get thaty if you included the dynojet carb jets

[dirtmomma]

Originally posted by 400exracer#19
75 for a stock 300 carb? keep dreaming..you could get thaty if you included the dynojet carb jets


Whatever :huh thanks! didn't say it was set in stone there pal!!

Throw a fit ;)

[wvspeedfreak]

Originally posted by 400exracer#19
75 for a stock 300 carb? keep dreaming..you could get thaty if you included the dynojet carb jets

I wouldn't be so sure about that.I just sold one on Ebay and it brought $110.A bone stock carb;)