250R Carb upgrade

[nuttynewt]

I'm in the process of upgrading my stock carb for a 38mm Airstryker. Will the jetting be totally different or somewhat comparible? If so, will they need to be bigger or smaller? I would guess bigger. I am curious to see if I need to go ahead and order more jets or not?

[wilkin250r]

Going from a smaller carb to a bigger carb, you need to get bigger jets.

What kind of engine do you have? Typically a 38mm carb is for a big bore motor like a 330cc or a 350cc, and not really so much for a stock 250r motor.

[deathman53]

not really, I have a 38 a/s on my atc250r, its bored 30 over, had one on my trx250r. if you look a 38 a/s is the most popular carb for 250r's. there must be a reason why, I kow mine is alot better than stock.

[airheadedduner]

The 38as is supposed to flow like a 36 at low rpm's and have the good top end the d-slide pwk's are known for. It is a good carb for most applications. You may need a couple sizes larger on the main and pilot, maybe a different needle. I would look into getting one from LRD, ESR or somewhere like that. Sometimes they supply some jets if you tell them what you have.

[powerslider]

Both my 38AS came with 170 mains and 50 pilots. My stock bore 88R with heavy engine mods but complete stock airbox/intake runs a 180 main and 48 pilot with the needle in the 3rd or 4th groove depending on air temps.

[Narly R]

They are right, it shouldnt hurt a stock engine. I have a 39mm PWK and I like it. But I have heard great things about the airstriker too.

[nuttynewt]

Thanks for the info. I am still running a stock cylinder on it's second bore, but it has been ported/polished plus I run an aftermarket pipe, reeds, ignition, head, rod, etc., etc. I know several people who run oversize carbs and they all have said that it improves power, but consumes more fuel.

[wilkin250r]

Don't get me wrong, it's not going to hurt the top end at all, but you'll lose some throttle response. You may not get out of the corners as fast, but you'll have better top-end.

[Geoff Thomas]

for a pretty inexpensiv carb get the stock 38mm pwk off a '99 CR250. If memory serves they are only about $150ish or less unless the price went up since I last checked. I'm running a 39mm Mikuni flat slide and she runs pretty good with it!

[macanic]

38a/s is a awsome carb
perfect for stock cyl.
good jetting 40-45 pilot
168-175 main

that should be perfect
porting will detmine the correct
remember a ported cyl will require less jetting.

Originally posted by macanic
38a/s is a awsome carb
perfect for stock cyl.
good jetting 40-45 pilot
168-175 main

that should be perfect
porting will detmine the correct
remember a ported cyl will require less jetting.
a ported cylinder will require just as much jetting as a stocker;)

[macanic]

i beg to differ....

i have def. proved this subject several.... times
now depending on your port job basic or full
with the use of a flow bench.

basic port matching like most people do....
no differance

full race porting
there's a difference...

fuel attimizes diff.