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General Category >> The Cafe >> Yoshimura MJN racing Carburetor
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Message started by paulmarshall on 01/22/15 at 12:17:43

Title: Yoshimura MJN racing Carburetor
Post by paulmarshall on 01/22/15 at 12:17:43

MJN Carburetor - Theory meets Practicality. Fujio Yoshimura figured out a way to create a Multiple Jet Nozzle that would be more efficient at atomizing fuel. It took a lot of engineering to develop and test the initial prototypes, but once dialed, the results were spectacular.

The key is a nozzle which replaces the standard tapered needle. The multiple jets spray a fine mist of fuel, which atomizes much better, thus creating a more efficient burn. In addition, the atomized fuel is centered in the bore of the carburetor thus taking advantage of much higher intake velocities creating even more power and efficiency.

Benefits of the MJN: MJN system atomizes fuel much better than ordinary solid type needles. The MJN nozzle controls the amount of fuel in proportion to the throttle opening (intake air) by accurately drilled and positioned fuel intake jet orifices. The resultant more efficiently atomized fuel gives better throttle response as well as better fuel efficiencies overall. Also, the MJN system supplies the fuel through the MJN nozzle in the center of the bore where air speed is the fastest. This atomizes fuel even better!

Another very important theory of MJN system is when the throttle is shut off and engine braking occurs, very minimal amount of fuel is guided into the intake ports. Therefore, remarkably crisp throttle response is obtained, upon corner exit and transition back to 100% throttle settings
(I copied the above statement from the YouTube clip)
https://www.youtube.com/watch?v=1HgXsgHSBbY

Title: Re: Yoshimura MJN racing Carburetor
Post by Dave on 01/22/15 at 12:51:22

Another very important theory of MJN system is when the throttle is shut off and engine braking occurs, very minimal amount of fuel is guided into the intake ports.

And that is what allows the backfire in our big single!

Title: Re: Yoshimura MJN racing Carburetor
Post by paulmarshall on 01/22/15 at 12:55:21

So its not worth the $400 plus dollars? I should stick with the Flat slide?

Title: Re: Yoshimura MJN racing Carburetor
Post by Dave on 01/22/15 at 16:31:45

I really can't find anything wrong with my Mikuni round slide. It was easy to jet, and works just fine. The jetting has already been worked out for you...you most likely just need a jet change or two to get it perfect.

I also can't find anything about a flat slide that would be a benefit on our bike. I can see if you have a Harley V-twin and the carb is hanging out in the breeze....the slimmer design of a flat side has some benefit - but it doesn't matter on the Savage.

Internet searches I did really didn't show the flat slide to be any better than a round slide.

http://www.dotheton.com/forum/index.php?topic=35175.0

You also need to consider how you ride....and what you are trying to achieve. I like to ride on twisty roads and feel the cornering forces. If I would guess ...I likely spend 90% of my time at 1/4 throttle or less cruising around the back roads, and even a stock engine makes plenty of power to satisfy that throttle setting. A few times I will open the throttle up pretty far to get up to speed from a stop......very rarely do I ever hold the throttle wide open for more than a gear or two. So 90% of the time a stock engine would do everything I need. What I have gained with my engine mods is a lot more torque, and the ability to have the Kawasaki pulleys that make it possible to cruise at 70 mph at a bit less than 4,000 rpm. It makes for a really relaxed cruise! 8-)

Title: Re: Yoshimura MJN racing Carburetor
Post by paulmarshall on 01/22/15 at 17:38:07

Hmm that's interesting Dave. So the three main differences are size and cost. Also the flat is a little more responsive due to having less travel under the flat slid compared to the round slide.