250r carb

[beak7707]

what carb do you guys think is the best to run on a 250r for woods, and all around good power. ESR told me the TMX would be the best but i never see any info on here about the TMX. Aren't air strykers pretty much for top end?

[2004TRX450R]

38 or 39 PWK air striker is what I think I would get. I'm probably going to get a '99 CR250 carb wich is a 39 PWK as I recall. They are really cheap for some reason!:D

[airheadedduner]

I prefer to stick with kehins. The 38 airstryker would be a good choice. It helps the bottom and with the PWK strenghs in the mid to top. I run a 35mm PWK. It is a nice improvement too from mid up. As long as you get away from the retarded oval slide. The tmx is a nice very carb though but mukuni jets are expensive.

[oldsandman]

I have the tmx on my r and it is a great carb. Wouldn't trade it for anything.

[AndrewRRR]

I don't have any Mikuni experience but the Keihin PWK's are nice. I had a 38mm A/S on my R and it had great bottom and mid with good top end.
The air strykers have fins that make the carb act smaller than it is on bottom end but still flow enough when you get into higher rpm ranges.
My '97 CR250 had a 38mm PWK but maybe the 99's are different. If I recall right there was something different about it between the CR's carb and the 38mm I got for my R.
Right now i'm using a ESR 40.5mm Keihin but i wouldnt' recommend it for bottom end or a 250.

[beak7707]

oldsandman do you have the 36 or 38 TMX.

[oldsandman]

Originally posted by beak7707
oldsandman do you have the 36 or 38 TMX.


38

[airheadedduner]

Originally posted by AndrewRRR

The air strykers have fins that make the carb act smaller than it is on bottom end but still flow enough when you get into higher rpm ranges.

New info I learned about the airstryker regarding the fins. While they do make the carb flow like a smaller carb at low RPM's(makes the 38 flow like a 36) that is not the main idea behind the fins. When air passes through the carb it picks up the fuel charge. When you go to a bigger carb you are getting a larger volume at a lower velocity. Because of that the carb cannot meter the air as efficiently and is not as quick to respond to a sudden change in throttle position. What the fins do is direct more of the air to pass over the metering passages of the carb so it responds more rapidly.

I got this from A. Grahm Bell's Two Storke: Performance Tuning handbook.

[AndrewRRR]

Originally posted by airheadedduner
New info I learned about the airstryker regarding the fins. While they do make the carb flow like a smaller carb at low RPM's(makes the 38 flow like a 36) that is not the main idea behind the fins. When air passes through the carb it picks up the fuel charge. When you go to a bigger carb you are getting a larger volume at a lower velocity. Because of that the carb cannot meter the air as efficiently and is not as quick to respond to a sudden change in throttle position. What the fins do is direct more of the air to pass over the metering passages of the carb so it responds more rapidly.

I got this from A. Grahm Bell's Two Storke: Performance Tuning handbook.

Yeah if you look at the fins there are two of them making a funnel right over the metering passage across the needle.
P.S.- That's a great book, I think I'm gonna read it again. I might get his four stroke tuning book too. It's also fun to watch brits spell things like carburettor and tyres. lol

[beak7707]

Do you guys think a 38mm carb would be too big for a stock motor. All i have is +.020, rad valves and an ESR TRX5 pipe. I have heard some people say until you port and polish or go big bore a bigger carb will hurt the motor. If this is the case i would probably go with the TMX 36mm.

[AndrewRRR]

Originally posted by beak7707
Do you guys think a 38mm carb would be too big for a stock motor. All i have is +.020, rad valves and an ESR TRX5 pipe. I have heard some people say until you port and polish or go big bore a bigger carb will hurt the motor. If this is the case i would probably go with the TMX 36mm.

Are you planning on porting for topend or going to a bigger bore? If you mostly ride woods and don't plan on going to a top end type port or big bore a 36 should suit you fine (You can also safely taper bore the stock 34mm PJ to a 36 if money is tight). It won't "hurt" the motor and I doubt a 38mm A/S would even make it blubber (I ran a 39mm on my R for a short time with no problems). I sold my 38 to a guy with a R that just had a pipe (no porting) and he said it really woke the bike up with no adverse affects.

[beak7707]

No top end, i plan on having it ported for low to mid. I dont plan on getting a new cylinder anytime soon, i have alot of life left on the stocker so im gonna keep it for a while. If i ever do get a diffferent cylinder i would probably go for the 265 pv. It sounds like alot more people are running the keihin, but ESR swears by the TMX for my type of riding.

[anotherMP250R]

I like the pwk's for gas. I have a 39 on my stock 86 play bike with an esr air filter kit and an old old LRD 300 big bore adjusted all the way out stock bore and no porting ran great .