Wb3a

Walt Gifford · Posted: Wed Oct 13, 2010 9:05 pm Post subject: Wb3a

How many Wb3a carbs do you own?

Gif Cool

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Jim White · Joined: 21 Jul 2001 Posts: 994

5 total.
How many do I use?
Only one.
It just seems to run and tune better than any of the others Very Happy

Brian Mead · Posted: Thu Oct 14, 2010 10:48 am Post subject:

6 plus parts for another and a good ol wb24. Still runs good btw.

Walt Gifford · Posted: Thu Oct 14, 2010 1:13 pm Post subject:

I'd have to go through a few boxes but I have about 10 but, I have 5 engines. It would be cool to dyno all 10, there has to be at least one really good one.

Gif Cool

John Mulvihill · Posted: Thu Oct 14, 2010 3:18 pm Post subject:

Hi Walt,

About a dozen. Track tested 8 of them a few years back. 6 were the same. One was a second faster. One was a second slower. Ran the fast one and the slow one against each other and there was two seconds difference.

I still haven't really figured out why. I've noticed variations in where the jets are drilled. And, when I spray carb cleaner through the passages the spray patterns differ.

With the dyno up and running this may be another winter project........

John
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Steve O'Hara · Posted: Thu Oct 14, 2010 11:27 pm Post subject:

John,

Just curious.... what kind of track did you do the testing on and how long does a lap take?
Steve O'Hara

John Mulvihill · Posted: Fri Oct 15, 2010 4:28 pm Post subject:

Hi Steve,

Roadracing at Daytona back when the event was longer and there was more practice time. Forgot the exact lap times but the driver was extremely consistant (better than me). 2.5 minute laptimes? The lap times of the good carb vs the 'other 6' was very consistently 1 second better. The bad carb was pretty much 1 second slower.

We then ran the good carb vs the bad carb within one practice session and there was two seconds difference,

This was without a trigger so we could switch them quickly. All of the carbs had fulcrum heights and pop-off's set as close as possible.

I'm sure that I didn't have all of the variables covered. So it was not as purely scientific as possble. That one good carb has seemed to be better than other carbs whenever I've been able to run it back to back against another. I'd love to know what makes it better so I could make others perform as well. Open to any and all suggestions.

Now that we can do some controlled testing, I can look for more 'good' carbs. However, it would be better ($$$$$) for most folks to be able to modify one carb rather than buying a bunch for testing.

Any thoughts?

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

Walt Gifford · Posted: Fri Oct 15, 2010 6:20 pm Post subject:

Here is what I suggest, send me the carb for a detailed examination under 5x magnification.

Gif Cool

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

Steve O'Hara · Posted: Fri Oct 15, 2010 10:46 pm Post subject:

John,

Back in the day when I was running the KT100s on the long road race tracks I had one carb that seemed to work better than the rest too.
One second on the long tracks sounds about right. I don't think it had anything to do with air flow rates but we never flow bench tested the carbs.
The good carb just seemed to tune better and the engine ran better through the acceleration sections but did not show higher peak rpm.
If I still had it I would send it to you to play around with but it is long gone now.
Keep us posted on your testing... it would be interesting to learn what you find.
Steve O'Hara

Kyle Prokup · Posted: Sat Oct 16, 2010 8:24 pm Post subject:

I believe we have 6 or 7, but I only use one. In the KPV classes, the one that I do use requires no leaning at the starts on the low speed. Its fast Twisted Evil

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Tony Kart EVRR

John Mulvihill · Posted: Sat Oct 16, 2010 9:04 pm Post subject:

Hi Steve,

I thought this link to Kinsler might have some bearing:

http://www.kinsler.com/Cat_32_Pgs/Cat_32_4_09_Pg_202.pdf

The drilled Walbro passages resemble the passage in the Kinsler article (that didn't have a radius) except that the Walbro passages are next to internal obstructions and have twists and turns.

When I have a chance, I'll do a visual comparison and see if anything is obvious. I have some jewelers loupes so I can do up to a 10X close-up look (Walt--I'll see your 5X and raise it to 10X<LOL>)

Its gonna be a long winter.......

John
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al nunley · Joined: 13 Nov 2006 Posts: 3038

JIM SILVERHEELS · Posted: Sun Oct 17, 2010 11:43 am Post subject: So

So the question is, what makes a Walbro atomize better.
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John Mulvihill · Posted: Sun Oct 17, 2010 12:50 pm Post subject:

Hi Al,

I use small reamers. but I have no idea what Walbro does. They may not really care that much since you have to drill a hole before it can be reamed. Just drilling would be so much easier.

Hi Jim,

Atomize better and deliver the fuel you need through the rpm range.

John
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I bowl overhand..........

al nunley · Joined: 13 Nov 2006 Posts: 3038