Carburetor options

[GheenoeRacer]

Anyone ever use a motorcycle slide type carburetor such as kehein mikuni or lectron on any 2 cylinder outboard?

[Team B&H]

Ever been to a PRO race? Slide carbs are all over- mostly Mikuni and Delorto and at least one guy has an engine with Lectrons, no Kehnin that I know of.

[DeanFHobart]

Is the carburetor on the Sidewinders butterfly or slide... It is a Mikuni... Is that correct?

[GheenoeRacer]

Lectron. They are nice but expensive. Mikuni are cheap. Measured my reed block and found a manifold flange cheap. Seems worth trying. The sidewinder uses a 30mm lectron on 15ci and 34 mm on 20 ci. Has anyone here tried this?

[dwhitford]

I think the Sidewinders use Del Ortos, 30mm on the ''B'' (20 c.i.) and smaller (24 mm maybe . . . ?) on the ''A''.

Sometime during the 1968-'72 window, I encountered a Canadian guy who had a slide-throttle Del Orto on his Looper.

Dissatisfied with the snowmobile diaphragm carbs that Chris put on my QZ 250 cc powerhead at his shop in Quincy in 1978, in 1985 I adapted a pair of brand-new 34 mm Mikuni round-slide carbs that had been pulled from a motorcycle in South Carolina. In those days the serious road racers were replacing the factory-installed Miks on their Yamahas with Lectrons before ever starting their bikes. I even put home-made power jets in my ''liberated'' Yamaha Miks..

It took me 3 roundtrips between Charlotte and central Florida to fully sort them on alky + 5% nitro, but finally they worked fantastic.

Mike Schmidt ''borrowed'' my engine to run RB for nearly 20 years and was able to win high points with it one year. He installed 36 mm flat-slide Miks to replace my round-slide 34s. Three years ago I replaced Mike's 36s with flat-slide 38s that are even faster.

Right b4 starting my MIK conversion in 1985, I had a 45-minute phone conversation with Roz, the Brit chief engineer at Lectron. She had no clue about how to advise me for a methanol conversion, so I promptly dropped that idea. But I'll bet that if some bright individual sweated thru making methanol meter right thru a Lectron, it would be a splendid outcome.

[1100-one]

Mikuni flat slides are great. Ran them on a 500 yamato. Took them off and put 4 snow mobile carbs on. You have to ask like your doing lots of knowledge here. Mike Schmidt very good there, Steve Litzel,Chuck and Neil LaRose, and many others. Good luck

[deeougee]

One thing when you are putting a new carb on is making sure it has the correct baffle inside the bowl for the fuel delivery system being used. Lot of guys will use a carb from a bike not realizing it has a baffle for a gravity fuel feed set up and use a fuel pump and wonder why they can't get the carb set up properly. Same goes for sled carbs. The reason for the flatslide is the shortened signal response time for fuel thus increasing low and mid-range power. My personal favorite is the Mikuni TMS-38. Very simple, in fact can go to the pro option jets to eliminate the main jet. A flat slide will also outflow an equivalent sized round slide by a wide margin and give you an increase in power across the whole band. Now you may also want to look at using a 34mm carb, bigger is not always better. Velocity threw the carb also plays a huge role in making HP in any engine and most people don't understand that either, especially in mostly stock engines. Good luck in your application.

[dwhitford]

Mikuni carbs from gravity-feed bike applications have large (3.2-3.4 mm) inlet needle-&-seat assemblies, such as on the 34mm Miks that I used on my methanol 250 engine in 1985-86. These inlet assemblies are far too big for pressure-feed or fuel-pump fuel delivery, even on methanol. I was then using pressure-feed fuel delivery, as I still do now. What I needed to do to sort those 34s was to make a fuel-pressure regulator calibrated at 1-1/4 to 1-1/2 pound . . . or about what the gravity-feed pressure was on the bike application.

For my flat-slide 36 mm and 38 mm Miks, I more recently discovered that I could use Mikuni's 2.0 mm pressure-feed inlet assemblies for sleds at full (unregulated) crankcase pressure, even though my main jet could be as large as 3.4-3.6 mm. In 1985 I knew that my main jets would be 'way bigger than 2.0 mm and was wary that the 2.0 mm pressure-feed inlet assemblies would starve the engine. Turns out not to be the case! Eliminating the pressure regulator was a major simplification and blessing.

[1100-one]

Very well said dwhitford. On my 500 I had 38 mm mikuni and ran a 3.0 or 2.9 and played with the power jets. Took those 4 carbs off and we t to a other style carb which I liked much better. Mike Krier, Bob Tadych abd I played with my carbs it seemed foe a long time to get them rt then I switched and my 38mm went to Krier