Lectron Carbs

[mattyslimz]

Since doing some more in depth carb options for 2-stroke scoots, I keep seeing Lectron all over the place. They mostly cater to the off-road world with self adjusting jetting for 2T bikes Cr250, Banshee, KTM Sx125 etc. 4T also. From what I can tell the smallest they produce is a 30mm. The 30 they claim is for minis 65 to 112cc i.e KTM SX65-Kawi KX100. KTM does make an SX 50 but is not mentioned on their site. Has anyone experimented or tried one of these on a scoot? And do you think the company would ever step in to the scooter realm? I really think it’s a revolutionary progression for carburetors especially in a world now where everything has become EFI.

[ThaiGyro]

Hey Matty! I have used Lectron's for many years. IMO, they are equal to or the best to work with. The flat slide carbs we used in the late 70's were 32mm, for a TA125 twin. So 15 to 16+ hp per cylinder sucking on a 32mm carb, or 62.5cc doing the same. The data you need is rpm/pipe/ignition related...for your intended tuning.

Let me state this: They are as good as the best FI systems, but better suited for 2 strokes...and simple to tune!Especially on a scoot.

Their 30 should be awesome, if you want a higher power band and say 12+ hp. That carb is quality. Plus, David and Kevin or their staff at Lectron will help you. Really! David is the CEO/GM, whatever, but a race freak. Kevin Gilham is the tech guy/tuner guru, whoset me up with Lectron's for my Yamaha TRX 850. (40mm X 2) Out of the box were good. Some minor tuning got me much power and awesome response!

Spendy, however.

They are in Texas. I-10, North of San Antonio.

[ThomasTPFL]

I know I’m oversimplifying, but they work like a Dellorto SHA?

[ThaiGyro]

No, not really. Lectron two stroke carbs are super air flow sensitive, (Good!) and more atmospheric tolerant IMO. Meaning, they still give good fuel draw and flow in ugly conditions, wheras many carbs cough and sputter.

They are flat-slide carbs like others. (who maybe copied them or the original EI, Keihin FCR...Mikuni BDST) The idea was started by Red Edmonston while he owned Edmonston Industries. (hence EI Carbs) Red used a system that worked more like FI but with no external pump, just similar (enhanced) differential pressure.

Lectron took that another step and has no main jet really. Mind you David and Kevin wee not the original owners, but have made great improvements to the carbs. The system uses flat tapered "metering rod" instead of round-taper needles. The variations to the actual taper length and cord are used to tune. The round side is the air-box side, the taper is on the engine side creating a super sensitive eddy air current.

The big difference from my view, is that the meter rod taper and it's micro adjustments are more simple and more effective. Idle to about 80% throttle +/- are done here. There is a "Power jet", so it is called, that is used for near WOT. It really adjusts differential pressure between the float bowl and the venturi, so you can dial in the top end flow of fuel when needed. In my experience, it rarely is an issue after initial setting. (Usually the ignition is shitting, not the fuel at WOT...take note!)



Now...the problems. They do not currently make a perfect size for a pumped up scoot All carbs are custom made and fine CNC machined. My KTM 65 has one and I paid $300 plus shipping/shitting cost. It makes 16+hp!! My TRX 850 carb set was over $2200, including spares and a new AFR sensor.

My thinking is that a Lectron will cause great smiles, once dialed in. But you need to be in the 65 to 80cc range with a real good pipe just to begin. The money is well spent! Our KTM 65 moto-crosser is faster and more reliable than anything else.

Oh...and uses less fuel/more air. My TRX has two 40's that flow more air than 42mm FCR's.

[90GTVert]

I checked out the Lectron carbs site not long ago because I've heard many great reviews of them. I saw that they were quite expensive and everything was huge compared to what I was looking for so I didn't put too much thought into it. ThaiGyro's comments about 12-16HP caught my interest though, because I would imagine my 103cc could get in the ballpark of that at least, so I sent them a message this morning. I told them that I have a 100cc scooter that makes roughly 15HP around 9,000-11,000RPM. I also told them that my current carb is a 21mm DellOrto PHBG and that I have used as large as a 28mm DellOrto in the past, but it didn't seem to do anything other than increase fuel consumption and lower CHT. This is the response that I just received :

"I wouldn’t recommend one of our carbs for your application until you are in the 30HP range."

So basically unless you have a high end racing setup, they wouldn't suggest it. I thanked him for the honesty and quick reply, but I must admit I felt a bit inadequate reading that. lol

[ThaiGyro]

I will send a note to Kevin and inquire. Yes, I think it is near overkill...and expensive, but the KTM SX65 kicks ass with that carb. So much improved over the OEM 24mm, or a PWK 28mm. It has a massive, short pipe and a custom mapped ignition.

I do think that Lectron could benefit from making a 28 or even smaller...but they are all about quality, so would not expect production. They build everything to order. The popular 28mm PWK is a close choice, but will not be quite as good.

The thing for us is...on 4T's we use smaller venturi Lectron's, as they flow more air. The fun thing for 2T'S is that they crave more air, so you just need the correct metering rod.

I do agree...you need to think high performance.  They are sooo easily tuned, however.  My money has been on them, but it is tough love on a 65cc 2T. Above that?  Best choice.

If Kevin didn't recommend a carb under 30 hp? Strange. Lectrons are everywhere in small bore MX. Maybe mis-communication/thought.

[190mech]

There is also the Smart carb which is similar to Lectron,also saw mention of the STIC mod for the Keihin PWK's that got good reviews;
www.vitalmx.com/forums/Tech-Help-Race-Shop,42/Smart-Carb-vs-Lectron-vs-Kitted-Stock,1314049
Smart has 25 and 28MM versions;
technologyelevated.com/shop/
Here is the STIC mod for you PWK guys;
www.hpracedevelopment.com/stic-metering-block.html

[ThaiGyro]

It is all interesting. The forums on Vital MX however are full of "urban legend" and useless conjecture.

The real deal is a combination of two things that are not simple: First, your selection should be based on "known" performance. (NOT SEEN YET) Second? How does one analyze the cost/benefit?

My dilemma on the TRX: Optimise the OEM 38mm CV carbs and gain...hmmm, not sure. Replace them with 42mm FCR's? Costly and poor economy, but better midrange. Lectrons? Even more costly than FCR's but smaller and near 10% better economy. More torque through rpm range. My bike is stock, mostly, and 23 years old, but gets 50mpg. Crisp and clean.

So, the thing to buy needs to have purpose and function and simplicity, at a cost that makes sense to YOU! I like simple. I am lazy. I like performance. I spend big money or value that lasts. My TA125, from 1975 had 30mm Lectrons. That bike is still running AHRMA events...with those same carbs. No Shit!

Of course, I hate urban legend...and I love data. Dyno data, race results, real hands on feedback. Find the cost/benefit ratio of Smart versus Lectron versus STIC/FCR mods. My guess? It is a figment of marketing imagination. I like what SMART has done...on a 50 year old design. Lectron is just that as well, but with no frills. The STIC? Cost to make an FCR act similar? Not a fan. Show me.

Show me st sea level...then high altitude...then 12% humidity and 70%...100 deg...then freezing. Do it all with a single dyno, if possible. Get my meaning? Fucking urban legend sells more useless shit than McD's.

The point? A Lectron, or maybe Smart, after setup, requires nothing except external tuning. You rarely have to remove the carb! Again, it is cost versus gain. Time/money.

[ThomasTPFL]

Googling I find reference on some forums to a 25mm Lectron, but nothing on their website. I guess it’s outbof production.

I also ran across the Tillotson TCT carb which looks interesting, but I’ve already got a old style pumper carb I have fooled with yet, so....

[mattyslimz]

ThaiGyro Wow thanks for the extra insight into these things, that metering rod is pretty interesting. Twin 40mm’s? I’m sure that thing screamed! One day I will visit SE Asia and see all the stuff they have to offer!

90GTVert (Mr.Brent) That was kind of a let down to hear something like that from them. Maybe soon if they get enough interest from the performance scoot enthusiasts that one day they may possibly make something reasonable for at least a mid-race set up. A lot of these new mini 2T mx bikes are using a power valve now, and are making big numbers as I’m sure your aware, hence they’re recommendation on 30hp or better. It didn’t cross my mind until after the fact. But if they set up something for say: KTM SX50 I don’t see it being a 30mm.

190mech and ThomasTPFL Any more info on these other brands such as price figures/availability?

[fast1075]

My personal experience with Lectrons is such that I would never consider using one on a street engine. The only real advantage I see is not needing a jet selection. Of course I am an old codger raised tuning VM Mikunis.


I ran several different sizes of Lectrons on various Kawasaki KZ drag bike engines varying in size from 903cc to 1428cc. Great for an application where anything other than WOT is irrelevant. Early production stuff was horrible for quality control. Unless they have been completely redesigned and had an actual idle circuit installed, I couldn't imagine sitting at a long traffic light without loading up and fouling a plug on a two stroke. Hopefully the new stuff is better.