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Discussion Starter #1 (Edited)
So with all the big bore options... what is everyone running for carbs? I know this has been covered but its 2020 and new tech is available. I’m currently running a bdt built 330 race gas 38mm pwk 178 mj 50p(+Pingel). It really likes the dgh needle on clip 3. I’m at 3200 ft and a good day of riding can take up to 6 or 7k feet. Has or is anyone running a lectron carb? I’ve seen good bike reviews. But will it work on the TRX?? To big of price for me to try. I’m also wanting big top end for street riding. Currently have lrd pipe and turbine core 2. I want a bdt pipe! at what point is a big bore pipe needed? I love the looks of those raw whale custom pipes. 🍻🍻
+ running hybrid CR bdt built ing(💪👌)
 

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I here a genuine Keihin PWK 38mm A/S is one of the best carbs for the TRX250R. I don't have a BB build but I do run a 38mm A/S carb on my set-up.
 

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So with all the big bore options... what is everyone running for carbs? I know this has been covered but its 2020 and new tech is available. I’m currently running a bdt built 330 race gas 38mm pwk 178 mj 50p(+Pingel). It really likes the dgh needle on clip 3. I’m at 3200 ft and a good day of riding can take up to 6 or 7k feet. Has or is anyone running a lectron carb? I’ve seen good bike reviews. But will it work on the TRX?? To big of price for me to try. I’m also wanting big top end for street riding. Currently have lrd pipe and turbine core 2. I want a bdt pipe! at what point is a big bore pipe needed? I love the looks of those raw whale custom pipes. 🍻🍻
+ running hybrid CR bdt built ing(💪👌)
I here a genuine Keihin PWK 38mm A/S is one of the best carbs for the TRX250R. I don't have a BB build but I do run a 38mm A/S carb on my set-up.
IMO...stick to Kehein or Mikuni 36-41MM depending on application, unless it's a Drag setup, then a Larger Lectron 44-50MM or bigger is in order.

Reason for Kehein & Mikuni is availability of parts; jets, needles, slides, ect...are available to everyone locally....any decent local motorcycle dealer stocks them as they are the most common to MX Bikes & Quads. And when you're in a bind, and can't wait for BDT's awesome Parts, Jetting & 1-2 day shipping :)cool: ), you can walk in locally and purchase what you need....

Woods: 36MM seems perfect for the low end response even for BB engines
MX: 38-39MM works good, OEM to BB engines
TT & FT: 39-41MM gives you the top end needed OEM to BB engines
Duner, General riding: 36-38MM seems almost perfect; based on engine size, work done, and riding style.

Carlos
 

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Been reading a lot of negative feedback on the lectrons. It's weird the dirt bike guys all run them and love them, but 250r guys can't them to perform right. I'm currently running the short body carb and it's truly amazing. My R is fat rich and it runs crisp. Where my 39 pwk I couldn't get it dialed in on the needle and it was blubbery.
 

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My boys stock cylinder R's and my 310 stroker have genuine keihin 38mm AS carbs. My 391 has a genuine keihin pwk bored to 40.5 mm. I feel keihin pwk carbs are the easiest to tune so I always use them. As an experiment I tried one of the $49.99 knockoff airstriker carbs from Ebay/Amazon. I gutted the carb and replaced everything with genuine keihin and it would not run! After messing with it for days I decided that the carb was a POS!
 
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My boys stock cylinder R's and my 310 stroker have genuine keihin 38mm AS carbs. My 391 has a genuine keihin pwk bored to 40.5 mm. I feel keihin pwk carbs are the easiest to tune so I always use them. As an experiment I tried one of the $49.99 knockoff airstriker carbs from Ebay/Amazon. I gutted the carb and replaced everything with genuine keihin and it would not run! After messing with it for days I decided that the carb was a POS!
WOW..."carb was a POS"; we AGREE :)

Been reading a lot of negative feedback on the lectrons. It's weird the dirt bike guys all run them and love them, but 250r guys can't them to perform right. I'm currently running the short body carb and it's truly amazing. My R is fat rich and it runs crisp. Where my 39 pwk I couldn't get it dialed in on the needle and it was blubbery.
I really push Kehein & Mikuni f(Kehein being #!) for the reason I stated; parts available locally vs Lectron. Nothing wrong with how Lectron's perform IMO.

Short Body Kehein's on a TRX250R are the very best in response....way better than regular Kehein's.

Carlos
 

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Been reading a lot of negative feedback on the lectrons. It's weird the dirt bike guys all run them and love them, but 250r guys can't them to perform right. I'm currently running the short body carb and it's truly amazing. My R is fat rich and it runs crisp. Where my 39 pwk I couldn't get it dialed in on the needle and it was blubbery.
agree.we did some back to back testing with a pwk then the sb carb and it's a night and day difference.we are also running pig rich due to new engine going straight to a race.but you would never tell unless you pull the plug.will never use anything but the sb carbs again.
 

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agree.we did some back to back testing with a pwk then the sb carb and it's a night and day difference.we are also running pig rich due to new engine going straight to a race.but you would never tell unless you pull the plug.will never use anything but the sb carbs again.
:)

Yea I think I will be getting one soon. Should I go 41 or 38 with my set up? And at what cc is a big bore pipe required?
Go with what your budget allows, and what you need. The 38MM SB Kehein is the least expensive, followed by the 39MM and 41MM. I would say for your application the 38MM or 39MM is fine.

Note the 38MM is the standard SB Kehein, 39MM and 41MM are Custom Cut SB carbs, and not available from Kehein, SUDCO, or anyone else that I know. BDT has the 38MM, 39MM and 41MM Kehein SB Carbs & Parts, Jet's, Needles, Cables in stock.

"Yea I think I will be getting one soon. Should I go 41 or 38 with my set up? And at what cc is a big bore pipe required?"

IMO...BB Pipes are from 292CC (310CC) on up. The Bigger the engine CC's, the larger the Pipe Volume, Stinger and Muffler Internal's should be. You can't expect a Pipe & Muffler designed for a 250-292CC engine to perform and run cool on a 330-370CC engine. The correct performing pipe for a smaller engine will increase back pressure tremendously on a BB engine generating a lot of extra heat...specially if you run in gravel, loose dirt or sand.

Carlos
 

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:)



Go with what your budget allows, and what you need. The 38MM SB Kehein is the least expensive, followed by the 39MM and 41MM. I would say for your application the 38MM or 39MM is fine.

Note the 38MM is the standard SB Kehein, 39MM and 41MM are Custom Cut SB carbs, and not available from Kehein, SUDCO, or anyone else that I know. BDT has the 38MM, 39MM and 41MM Kehein SB Carbs & Parts, Jet's, Needles, Cables in stock.

"Yea I think I will be getting one soon. Should I go 41 or 38 with my set up? And at what cc is a big bore pipe required?"

IMO...BB Pipes are from 292CC (310CC) on up. The Bigger the engine CC's, the larger the Pipe Volume, Stinger and Muffler Internal's should be. You can't expect a Pipe & Muffler designed for a 250-292CC engine to perform and run cool on a 330-370CC engine. The correct performing pipe for a smaller engine will increase back pressure tremendously on a BB engine generating a lot of extra heat...specially if you run in gravel, loose dirt or sand.

Carlos
Carlos, when you state " standard SB Keihin" above. What does the SB mean? Short body? Standard bore? I am currently on the lookout for a 38mm Keihin but confused on the descriptions. Are short body Keihin Air Strikers too? Going on a '85 ATC, do I need the short body for clearance?
Thanks,
John
 

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Carlos, when you state " standard SB Keihin" above. What does the SB mean? Short body? Standard bore? I am currently on the lookout for a 38mm Keihin but confused on the descriptions. Are short body Keihin Air Strikers too? Going on a '85 ATC, do I need the short body for clearance?
Thanks,
John
SB = Short Body, in BDT Lingo :)

Keihin SB's are made in Japan and imported by SUDCO, IMO the SB's are the best carburetor to date for the 250R specially for racing Woods, XC, TT, FT, or MX. Very responsive, quicker throttle action than AS or PWK or any of the TM/TMX Mikuni's.

They are available only as 38MM in the US from SUDCO unless you special order out of Japan. BDT has the SB's in stock, special ordered from Japan in 38MM, 39MM, 40MM and 41.5MM. They are much higher priced than Kehein PWK & AS.

Unfortunately, currently they cannot be used in an ATC250R, only in a TRX250R....reason being they are taller (as well as shorter in width) than the PWK & AS and interfere severely with the upper Frame tube on an ATC250R.

Carlos
 

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JetRus has the 38 as short body for $329.99. They have the regular 38 airstriker carb for $269.99.
Eddie Sanders has the 38 airstriker short body for $329.00 and the regular 38 airstriker carb for $279.00 and it comes with a free jet wrench and a set of jets. You just pick your engine size range and ESR sends you jets for that.
I'm always on the lookout for a better deal as I have 3 trx250r's and 2 atc250r's that I am either building or maintaining.
Loren
 

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WOW..."carb was a POS"; we AGREE :)



I really push Kehein & Mikuni f(Kehein being #!) for the reason I stated; parts available locally vs Lectron. Nothing wrong with how Lectron's perform IMO.

Short Body Kehein's on a TRX250R are the very best in response....way better than regular Kehein's.

Carlos
What causes the shorty to be different/better? And is it better for the ATC as well?

I have no issues with my standard 38 PWK, just asking to learn something.
 

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Eddie Sanders talked to me for about an hour last August at the Oregon dunes trx250r meet about short body carbs, his ceo design, and atc racing back when it first started. He runs a short body carb on his 391 ceo. His bike absolutely rips! He has the trx10 pipe on it.
He said he jet his carburetor by himself. So I guess I am not the only guy that can jet his own carb lol. Eddie can do it too!
Loren
 

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I don't think it's a matter of not being able to jet, more a matter of some not having the time or experience, others would just rather have a Builder jet and setup their carbs, answer questions or concerns directly related to a 250R....really nothing more.

At BDT we pride our self's in being able to provide what other Builders, Shops or Parts suppliers can't or won't; we don't just sell parts, or carburetors; we make sure each is setup specifically for the customers 250R based on engine size, fuel, humidity, temperature, altitude, riding venue and style, even overall rider & machine weight...I don't believe anyone else is into the details of fuel delivery as BDT is...a result of all the Racing we are involved with.

At the end; purchase what you want from who you want, and when you have issues; call the 'Best, call BDT :)

Our Short Body (SB) Prices, Pre-Jetted, setup for your specific 250R:

SB BDT Kehein 38: $359.99
SB BDT Kehein 39: $365.99
SB BDT Kehein 40: $375.90
SB BDT Kehein 41.5: $385.90

Carlos
 

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we tested themback to back last year and it was a huge imporvement.willnever run a regulas a/s carb again.
Interesting how you see posts from some that have never run a SB vs a Standard carburetor, as well as other Performance components, pipes, engines, IGN's and feel what they have is already 'good enough'; you really don't know till you test it on the Dyno and at the Track.

IMO a big advantage for BDT is having racers across the country regularly Testing & Racing 2 Strokes-250R's, like Cody, Dave, Chris, Jeff, Ben, Chad, Mike, John, Anthony, On-N-On....regular input from the Top Racers is most important in Engine development & Performance gains.

Carlos
 
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