stock "lean burn" Carbs ??

[dirkdiggler]

I have heard Chuckie refer to some stock mikuni 44 carbs being "Lean Burn".

Are all stock dual 44 carbs "lean Burn" carbs or just certain ones? Is there a visual way to check?

 

[Foximus]

OEM 760 ones. Yamaha ordered them that way. Check under the butterfly, there is one less idle circuit drilled.

 

[waxhead]

Yes stock 44s for a 760 are crap
I will do you a favor and take them off your hands

 

[Foximus]

i'm eventually going to turn mine to blackjacks. =]

 

[kevbo]

The 44s that yamaha uses are SBNs with different plates. I have had no trouble making them fourcycle at part throttle, where they are suppose to run leaner than aftermarket versions. The I body mikunis are designed for and do run leaner above 1/4 throttle. Mikuni I40 that are stock on SXRs and seados work fairly well because of their small size . Mikuni I44 and I46 can be difficult to make rich enough over 1/4 throttle. Engine size and the flame arrestor play a larger role in making them work.

 

[waxhead]

The 44s that yamaha uses are SBNs with different plates. I have had no trouble making them fourcycle at part throttle, where they are suppose to run leaner than aftermarket versions. The I body mikunis are designed for and do run leaner above 1/4 throttle. Mikuni I40 that are stock on SXRs and seados work fairly well because of their small size . Mikuni I44 and I46 can be difficult to make rich enough over 1/4 throttle. Engine size and the flame arrestor play a larger role in making them work.

Yup your right
I never seem to have an issue getting these things to make power ethier

 

[dirkdiggler]

so the stock dual 44's on the 760 motors have the 3 tiny holes and the other dual 44's have the 4 tiny hole circuitry?

 

[SUPERTUNE]

so the stock dual 44's on the 760 motors have the 3 tiny holes and the other dual 44's have the 4 tiny hole circuitry?

Correct. 4 hole circuit with the aftermarket 44's and 46's
Actually a 6M6 carb off a stock 650 Yamaha is a 4 hole and the 61X 701 carb is a 3 hole circuit.

 

[waxhead]

They are called progression ports they are designed to supply the fuel before the low speed jet gets enough signal to flow

 

[iptamenos]

what is "Lean Burn"

 

[dirkdiggler]

The stock carbs run lean in the mid range becasue the ski they were made for run at WOT most of the time .......... not sure if this is right......Im sure Supertune(chuckie) knows the real reason?

 

[dirkdiggler]

What are the risks of running the stock dual 44 carbs(3 tiny holes) from GP760 vs. aftermarket dual 44 carbs with (4 tiny holes).

Is there anyway to set them up so they dont "lean burn" the motor?

 

[Foximus]

There are no risks that arent inherent with any other non properly tuned carb. its not like the term "lean burn" means they are ticking time bombs... it just means they probably run at a 15-16:1 AFR instead of a 13-14:1.

 

[dirkdiggler]

then why do people say stay away from them and get the (4 tiny hole) ones?

 

[Foximus]

Cause chuckie made a big hype about them on how much they suck... If you remember a few years ago a set would go for no less than 200... now you can barely get 120 for a nice pair.... Its all about marketing.

Sure they arnt the best but so what... neither is an msd enhancer, or boysen reeds.

 

[Motorheads5]

Dirk I am looking for a pair and I have $125.00 shipped of course freshwater only carb's wanted.

 

[motoman96]

What about the 46SBN on the wetjet intakes? I guess I could just go look as its in my garage.lol

 

[Foximus]

a 46 is a 46. no difference in those.

 

[2XLR8]

a 46 is a 46. no difference in those.

The wet jet 46's don't have extended shafts and I have seen the base bolt hole pattern being wider.

 

[motoman96]

The 46SBN's on the wetjet intakes have a much wider mounting location than any other 44 or 46SBN.