Wb3a

Gordon Duax · Posted: Tue Nov 09, 2010 8:52 pm Post subject:

I was just looking through an old ('93) Walbro service book at WB carbs, and besides the WB3A, there are/were several other WB models listed as 'racing kart' carbs.
Some of them with larger venturi diameters.
WB3A has a venturi diameter of 23.8mm.
WB7,8, and 13 have a 25.4mm venturi,
and the WB18 & 20 have a 26mm venturi.

The WB7 was listed for a Noguchi kart engine.
The WB8 was listed for a Carroll kart engine.
The WB13 was listed for another Yamaha,
with the Yamaha p/n being 7KO-14501-00, and engine model OK64 (?)
The WB18 listed as for a Showa, with the p/n almost identical to the Yamaha, 7KO-14501-01
WB20 also for a Showa kart engine.

Seems to be some opening here for stock appearing classes.
I have no idea if any of these are still available........

al nunley · Joined: 13 Nov 2006 Posts: 3037

Sounds interesting. An information, or pictures, on the pumping capacity? Any of these carbs have double pumpers?

Thanks for the posting.
_________________
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 · Posted: Wed Nov 10, 2010 9:53 am Post subject:

Been doing some digging since last night, and what I found is that all of them look identical to the WB3a.

There is a kart shop in the mid west that has the WB-20 for about $73 each.
http://www.clearlight.com/~laukrace/walbro.htm

They do show that the pump cover is a different part number.

But forum posts I've found on it, dating back to '07 time frame says that they didn't work out to well.
For what reason, I don't know for sure.
Considering the source, it just may have been something simple like incorrect pop-off, or the failure to open the flow path up from the throttle, all the way to the piston, etc..
Hell, if this was the 1950's, there would be people swearing that tuned pipes are a waste of time......
Sometimes it just takes the right person to figure it out.

Colin Edwards · Posted: Wed Nov 10, 2010 3:44 pm Post subject:

Need to factor in the fact the WB3A was designed primarily as a chain saw carby. Not too much need for the tight tolerances you would expect from a carby designed for competition bikes / karts like say the Dellorto VHSB on a Rotax!
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Gordon Duax · Posted: Thu Nov 11, 2010 11:26 am Post subject:

LoL !

I still have a couple of 'chainsaw' engines that will outrun any piston port Laughing

John Mulvihill · Posted: Fri Nov 12, 2010 9:31 pm Post subject:

But, what about the kart motors made into competition chainsaws?

Can I get anybody to look into their good carbs and report back?

Come on, its just a few screws........

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

JIM SILVERHEELS · Posted: Sat Nov 13, 2010 4:45 am Post subject: HUH

Name one chainsaw or string trimmer the 3a is on.
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Gordon Duax · Posted: Sat Nov 13, 2010 9:22 pm Post subject:

I think Colin was reffering to that series of carb, the WB......
And yes, many of the WB series (with the exact same venturi size as the WB3A) are listed as saw carbs.

Stange thing is that the Mugen kart engine came with a WB3A on it......
So it can't be all that bad.

Mike Arnold · Posted: Fri Jul 13, 2012 9:43 am Post subject: Blueprint Carb's

Reading through all of this....is it possible to blueprint or modify a stock carb into a much better carb?

Are higher dollar carb's better than the $75 stock carbs?

Mike

al nunley · Joined: 13 Nov 2006 Posts: 3037