Wb3a

[JIM SILVERHEELS]

Always wondered why the WKA rules would have us use an inlet carb cup like they do when they could use a velocity stack.
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Don't get stuck in someone else's discarded chewing gum with your thought process.

[John Mulvihill]

Hi Jim,

For a while there was the "Pipe of the Month Club". With little effort we could add the "Velocity Stack of the Month Club"<LOL>

We could have a bucket full of velocity stacks to match the barrel(s) of pipes some of us have........

I was doing this when the velocity stack rule came in. Basically there were a bunch of 'cups' already on the market and some people were starting to make velocity stacks of different types. It was done to save the racer a few bucks. One of the few things along those lines.<LOL>

Have you seen any of the new "Big Mouth" air filters? It goes on....


Mark,

Please take a look in your known JUNK carb and let us know what causes it to be bad. Much appreciated.

I've been looking in 13 carbs so far and I'll post some pics later from my best carb. A picture is worth a thousand words.

Thanks,
John
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I bowl overhand..........

[JIM SILVERHEELS]

Now that the Yamaha Pipe class is done in Man Cup I guess I'll have to get another can carb done. In everyone's opinion is it necessary to do this or... will a pipe carb do the trick? Where should the lever and popoff be set for can? thanks
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Don't get stuck in someone else's discarded chewing gum with your thought process.

[Gordon Duax]

[Mark Horne]

John,
Just looking at the junk carb you would think it would be a good one. It has a clean casting and the Venturi looks good. Go figure.

I know it is bad because it does not make much power and is VERY hard to adjust the needles for a smooth power curve with ANY exhaust.


Jim,
A good carb will work with any exhaust, at least it should. The only thing you should have to do is set the pop-off around 10.5-11.5psi for the can.


Have a great day,
Mark
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SLK PowerLab
2 Cycle Dyno Tuning

"Racing is life,.....everything else is just waiting"
Steve McQueen - LeMans

"There are only two things that make feel alive, racing is one of them."

[Walt Gifford]

You don't need new tires or the driver to be consistent to check a carb with my egt method, you're not checking lap times. You read the data from clutch stall to some predetermined max rpm on the straight then examine the curve to see if the egt is optimum at all points. You have to keep notes on where the needles are set and which laps you make adjustments. Rpm data is really all you need, egt is nice but, rpm vs time is what gets you down the road.

Gif
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FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience

[Todd Bellew]

If the wind is blowing the data is junk for what you're trying to see. Plus, all a driver needs to do is open the throttle 5 feet earlier or 5 feet later and egt curves are not going to be good for small differences. Braking later can even change egt on proceeding straights.

It's possible but, track testing engine parts that have fractional increases in performance is next to impossible. And anything you said you learned from track testing engine parts I'd take with a grain of salt and wonder which of the 1000's of variables seeped into your track testing.


Think about what percentage of error egts temps have and then look at the percentage of change you're trying to measure and see if the gauge can even measure that small. And whatever percentage you're dealing with is the limit of accuracy you can achieve.

You can see large differences but, a driver and overall laps times can tell you you've made a big change. But, the battle is adding up the small ones.
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Thank You,
Todd Bellew

[John Mulvihill]

How I spent my evening......

Box O'Carbs

[img]

Pics from my best carb based upon back-to-back track testing. Along with my "observations". I'd like to hear from you guys about how they compare to your Good or Bad carbs. Come on, pop your's open and look.

Idle correction jet feeding into emulsion trough. The air correction orifice is centered nicely on the low speed orifice, which is centered in the trough floor in terms of distance from the trough walls. The air correction orifice is also fairly low and close to the trough floor compared to other carbs.

[/img]

Hole in back of emulsion trough that feeds the idle jet. There appears to be an inconsistency in the location of where the hole is drilled in raltionship to the floor of the trough. In this carb the hole actually intersects the floor. In other carbs the hole is drilled higher and there is a 'step up' from the trough floor.



Not sure if any of these variations makes a difference<LOL> What have you found?

Walt, Dyno pulls and on track will find the best carbs. 100% agreement that they will eventually float to the top. I'm just trying to figure what makes a Good carb good and a Bad carb bad. The long term intent is to figure out how a Bad carb could be rehabilitated and take its proper place in society. Better than buying a dozen carbs to find good ones.

Thanks,
John

[Walt Gifford]

What was the other method again, looking down the bore of the carb with a strobe light to see how much fuel is spraying out? I guess there's more than one way to do something.

Gif
_________________
FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience

[Gordon Duax]

It looks like Baroni & Tryton both make billet versions of the WB,
But they are $400 carbs.....
The Baroni has an extra pumper plate, which is interresting.
Here are some pictures:

[al nunley]

Our prayers have been answered. Our prayers have been answered. Maybe.
The 100cc piston port pipe classes could sure use something like that. Test's should be conducted to see if they would be better. Not faster, just better.
You want to balance out the competition in those classes, this might be the way.
Duel pumper’s, just like the Mc101. We never had any trouble delivering enough fuel, (alky) with those. It sure made the tuning a lot easier.
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If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

[Gordon Duax]

[John Mulvihill]

Hi Gordon,

Mitey purty carbs.......

Any idea what they are made for? Is there a class somewhere in the world where they can be used?

Thanks,
John
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I bowl overhand..........

[Gordon Duax]

These were in the UK, and they run a 115cc piston port class there.
(I guess to use up all the old BT82s)
But not sure.......
Maybe for the modern PPs, like the Parilla Swift.

[Gordon Duax]