Smart Carb Feedback

[christph]

I know there was a lot of excitement about the Smart Carb a while back, so now that I'm in the market for a new carburetor I'm wondering if they lived up to the hype? I know they had a problem with supply early on, people waiting months to get one. I just visited their website and it looks like they have their act together--no more long wait periods. I'm interested in the cast model. I heard the billet model allows for tighter tolerances but it is also more expensive by a couple hundred dollars. They also have a new casting supplier and it sounds like they fixed any earlier problems they had. Anyway, my question is whether it offers superior performance to a Keihin or Mukuni?

[Skeans1]

I know there was a lot of excitement about the Smart Carb a while back, so now that I'm in the market for a new carburetor I'm wondering if they lived up to the hype? I know they had a problem with supply early on, people waiting months to get one. I just visited their website and it looks like they have their act together--no more long wait periods. I'm interested in the cast model. I heard the billet model allows for tighter tolerances but it is also more expensive by a couple hundred dollars. They also have a new casting supplier and it sounds like they fixed any earlier problems they had. Anyway, my question is whether it offers superior performance to a Keihin or Mukuni?

I personally got rid of my 40 billet and went to a lectron in a larger size,  I know on the bigger motors they don't work the best what size motor are you going to put it on?

[Big_Mike]

Jeremy how do you prefer the lectron over a PWK?  Worth the switch over?

[Skeans1]

Jeremy how do you prefer the lectron over a PWK?  Worth the switch over?

Jeremy? I'm Jared Had a few pwk over the years they're okay the lectron works well too its personal preference and application.

[Jerry Hall]

The Mikuni TM38 and 39 PWK when bored to 41.5 to will flow enough air to make about 65 hp on gas when plugged in to a V3 reed on a big bore 250R. If your 250R big bore Honda has the capability to make 75 HP to 80 HP when plugged into a V3 reed, you will need something like a VM44 Mikuni or Lectron 48 which has an effective bore of 43mm to 44mm.  

When all of the components are perfectly matched and working together, I have seen a few 500cc singles produce 90 hp on gas with a 48 lectron when plugged into a V2 reed.  It will take a carburetor or throttle body with an effective flow diameter of 52 to 53mm to produce around 100 hp on gas.

Lectron makes some large billet carburetors.  Their largest carb is called a 58mm and has an effective flow diameter of 53mm to 54mm.

The bottom line is it takes a certain amount of airflow through the carburetor to produce one horsepower.  It takes a certain amount of fuel to produce one horsepower.  Air flow is mainly dependant upon the minimum diameter of the airflow passageway through the carburetor.  Making a carburetor meter the precise amount of fuel at all throttle positions and airflow rates is the goal of all carburetor and fuel injection system manufacturers.  Every manufacturer has what they think is a unique design and reason as to why their carburetor is superior to all others.  

I has been my experience that most carburetors  built over the last 30 years have the ability to meter fuel fairly well when placed in the hands of a veteran tuner and dismal results when put in the hands of armchair tuners.  

My advice is to buy a carburetor that is priced to fit your budget that has a large assortment of tuning parts available from the manufacturer. Spend and or invest in the necessary time learning how to tune it.  You will be amazed how well the cheap carburetors run when properly tuned.

[hontrx265r]

Seems like most of the guys that had them have switched to something else. Like Jerry stated I think the most important thing is having the proper parts needed to tune. It seems smart to look around at the people you ride with and see what they have. When your around camp and suddenly need a jet, or needle, you dont want to be the odd man out.

[christph]

I actually have Keihin and Mukuni carbs on my various quads and 3 wheelers, e.g., PWK, TM, and TMX.  I'm good at jetting and like them all.  I'm just looking to experiment with something different so I thought I might try the Smart Carb.  I suppose I could look at Lectron as well but I thought the Smart Carb was supposed to  represent an advance over previous single circuit designs.

[rablack21]

I actually have Keihin and Mukuni carbs on my various quads and 3 wheelers, e.g., PWK, TM, and TMX.  I'm good at jetting and like them all.  I'm just looking to experiment with something different so I thought I might try the Smart Carb.  I suppose I could look at Lectron as well but I thought the Smart Carb was supposed to  represent an advance over previous single circuit designs.

What size motor are you running? I have ran the 38 cast SC and the 40mm Billet SC. They ran absolutely flawless on my 310pv engine. I had a little more trouble with my 363 engine, but it still ran strong. No carb is plug and play. A little tuning is gonna be required. The difference will be, once you get the SC set, you won't have to change it again for temperature and elevation. It will perform the same every day. The other carbs won't give you that. You also don't need a bunch of pilot jets, and needles, and main jets. You can fine tune it with an adjustable clicker on the top of the carb. If for some reason you need a different metering rod than what it calls for, you can put a payment down for a new one. Then when you send the previous one back in, you get your money back. So you aren't paying for a bunch of extra parts. No other carb company will do that for you either.

Yes, the SC's foundation begins with similarities of the Lectron, but then it becomes unique from there. Here is some of the history if you are interested in reading.
http://trx250r.org/threads/4766-APT-Smart-Carb-History-Design-and-Tuning-Tips?highlight=smart+carb

[Skeans1]

What size motor are you running? I have ran the 38 cast SC and the 40mm Billet SC. They ran absolutely flawless on my 310pv engine. I had a little more trouble with my 363 engine, but it still ran strong. No carb is plug and play. A little tuning is gonna be required. The difference will be, once you get the SC set, you won't have to change it again for temperature and elevation. It will perform the same every day. The other carbs won't give you that. You also don't need a bunch of pilot jets, and needles, and main jets. You can fine tune it with an adjustable clicker on the top of the carb. If for some reason you need a different metering rod than what it calls for, you can put a payment down for a new one. Then when you send the previous one back in, you get your money back. So you aren't paying for a bunch of extra parts. No other carb company will do that for you either.

Yes, the SC's foundation begins with similarities of the Lectron, but then it becomes unique from there. Here is some of the history if you are interested in reading.
http://trx250r.org/threads/4766-APT-Smart-Carb-History-Design-and-Tuning-Tips?highlight=smart+carb

Ryan I had to adjust mine for temp differences and humidity changes.

[rablack21]

Ryan I had to adjust mine for temp differences and humidity changes.

Then something was never right with yours to begin with. They ran these things multiple times in the Pike's Peak races on two different quads, 1 2 stroke and 1 4 stroke. And they ran the same from top to bottom, which are large elevation and temperature differences. I never adjusted mine when I was racing mx on my 310. Some races were in the 30's °F and some races were in the 90's. Mine ran the same year round.

[The_Steve_Man]

I am also thinking about getting one to try out, but probably next year.  Ryan which route would you go again, the cast or the billet?

[christph]

I was thinking about running it on my Duncan PC2000 340.  Currently I have a 39mm Keihin PWK on it and it runs great.  I'm just in an experimental mood and remember a lot of excitement about the Smart carb.

[rablack21]

I am also thinking about getting one to try out, but probably next year.  Ryan which route would you go again, the cast or the billet?

I would go by the carb size that you need and not be concerned about cast or billet. The cast one was just as reliable as the billet one from my experience.

[The_Steve_Man]

I would go by the carb size that you need and not be concerned about cast or billet. The cast one was just as reliable as the billet one from my experience.

Great. Thanks.