Which carby? whats the difference?

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J

James

Well-Known Member
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it seems there's half a dozen walbro carburettors listed for 2 stroke RC cars...

whats the best option? what are the differences?

this is for a 26cc FS racing truck, that I'm working on the basis has a dud carby, and can't be bothered stuffing around with it anymore!

I have a "good" exhaust for it, but its not currently fitted.

thanks!
 
"The calibrations for both the WT-603B and WT-668B are the same with the exception of the third idle hole.
The 3rd idle hole in the WT-603B is .55mm and the 3rd idle hole in the WT-668B is .60mm"

why does one seem to be more expensive then? or, is it just a case of "because it can be"?
 
"the WT-813 will not give you anymore speed, it gives better takeoff from down low due to the accelerator pump but the rest of the carbie is essentially the same as the 668, same venturi size etc.
It may flow a little better due to having no choke plate but I seriously doubt it would really make that much difference in real world applications."

which makes it somewhat appearing to me, being in such a heavy truck...
but then the lack of a choke is a bit annoying...
 
"Guys I have just replaced my stock ss carb with walbro wt-813 and i cant notice any difference with it whatsoever apart from its real female dog to start.
With the old carb i could always start with no more than 5 pulls now with the new carb anything from 5-15 when cold.
Have i done someting wrong , please could you post some opinions and feedback im thinking of putting the old carb back on "

lolz :p
 
I've read all manner of things regarding venturi dimensions, but that was my basic, and admittedly ignorant opinion earlier on .... stand by it!!

For starting, you need to prime the 813 3 or 4 times using the servo / throttle before you fire it up, then it's easy.

Al.
 
guys my carb on my cc promod has no choke due to being racing carb, I prime the bulb, prime the chamber, and it fires up in 2 pulls even when cold.
 
The calibrations for both the WT-603B and WT-668B are the same with the exception of the third idle hole.
The 3rd idle hole in the WT-603B is .55mm and the 3rd idle hole in the WT-668B is .60mm
Walbro WT-813 HP carburetor for RC engines. Features a 5/8" bore and 1/2" venturi as well as a built in accelerator pump for quicker throttle response. High and low speed fuel adjustment screws.
Walbro WT-990 high-performance carburetor. This is the carburetor recommended by Zenoah for upgrading your RC-style engine. Engines with the standard carburetor (WT-603, WT-668, etc) tend to experience a lag in low-end acceleration when tuned for peak power. Carburetor specs: Walbro WT-990. 15.88mm bore, 12.7mm venturi, independent tunable high and low speed jets. This carburator does not have an internal choke. The WT-990 Carburetor is the same as the WT-813 WITHOUT an internal acceleration pump.


J.;)
 
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I did notice changing from the 603 to a 813 on my then standard G260RC Zenoah, that the 'near optimum' settings changed from ~1.2 LOW / ~1.3 HIGH to ~1.1 LOW / ~1.2 HIGH - slightly screwed in relatively.

I've now fitted a 2 bolt 28.5cc Trevor Simpson reed engine and it appears to be running OK on ~1.3 / ~1.5 LOW / HIGH on the 813 - considerably richer.
Probably not ideal as I'm no expert but these are the apparent observations I've noticed.

Al.
 
I think my Zenoah engines have come standard with either 603 668, I can't remember which one it is I'd have to check when I get home.

Which ever one it is, I've never has an issue in any of my race cars and 90% of them have been tuned/modified and the chokes removed.
 
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