# Walbro rotary throttle valve?



## luckyvision (May 24, 2007)

I'm working on a Shindawa trimmer with a Walbro carb # YWL-26A rotary throttle valve.

no high or low adjustment screws on this carb.

the unit won't idle, took carb apart cleaned it (looked very good) reassembled all parts in the correct order. careful to not bend the metering lever.

reassembled, no change.

holding throttle as low as it will go without stalling, a shot of carb cleaner in the throat of the carb revs the engine.

so, looking for an air leak found the throttle valve leaks between the mount plate & valve shaft. I do have some side to side movement. 

looks like it's all one piece (pressed together).
walbro says there is an idle adjustment under the top cap, but this unit had no top cap, & it looks (factory) as if the brass piece in the center is a what i call a "B-B" plug. 

do these come apart?

walbro lists a wyl-26*"C"* on their site, not an *"A".*

*would the throttle valve be interchangable?*

Thanks, --Lucky


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## paulr44 (Oct 14, 2008)

Those carbs can be tough to get working properly. The IPL is here: http://wem.walbro.com/walbro/product2.asp?Series=WYL&partnum=WYL-26-1.
Only OEMs use letters after a Walbro carb model number. Walbro aftermarket carbs will come as a WYL-26-1 on the box, although what's in the box may be a WYL-26B. It just has to do with their distribution conventions, that's all.

If there's a BB plug on top like you cite, then there's no way to alter the mixture with a standard adjustment. Betcha this is a T-20 unit...

Paul


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## luckyvision (May 24, 2007)

Talk about timming, i just refreshed & saw your reply, lol.

I got a new rotary valve, it's adjustable.
this one is threaded above the needle. 
according to Walbros service manual, it should either have a fine tuning adjustment above the needle, or a cap.
don't know which this should have.

anyway, here's what i have now:
--needle & idle adjustment are VERY touchy.
--i can get it to idle or scream but not both.
--if i 'set' it for high rpm running, it's only at half throttle.
- at no point can i get it to go full throttle without stalling.

-i'm thinking the inlet needle lever is set too low (lean)

thoughts?

btw, the needle adjustment is very loose, it seems just the vibration from the machine would change it...

does there need to be a cap or fine adjustment screw to keep it from drawing air (lean out?

Thoughts?

Thanks!


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## luckyvision (May 24, 2007)

according to a Goggle search, t-20 is a butterfly carb not rotary..


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## paulr44 (Oct 14, 2008)

No no no. T-20, as in Shindaiwa T-20 trimmer. (http://www.shindaiwa.com/usa/en/_docs/ipls/trimmers/t20.pdf). I used to sell them in the 80's.
Anyway, you may have a CC (crankcase) leak. Get it to idle, and CAREFULLY spray some carb cleaner around the crank seals, you can usually get at the PTO end through the cooling air grille area below and left of the carb, (may not be able to at recoil side one unless you remove it after you get it running, requiring SOME caution), then move onto the intake manifold area. Look for a change in RPM.

It could still be a carb issue, but having done 2-stroke for years, I ALWAYS check for vacuum leaks first, as it can mimic a carb problem.

You could do a CC pressure/vacuum test, but that requires special equipment and carb. cleaner is a quick, down & dirty way to find most leaks.

*CAUTION !!!* Spray carb cleaners are usually flammable, and the muffler being hot, well, just do the test outside in case you catch it on fire, be careful where you spray and have an extinguisher handy.


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## luckyvision (May 24, 2007)

oh yeah, t-20 duh! lol

i already did the spray test, but i'll recheck. i have the pressure/vac test for Stihl (i'm a dealer) i'll see if one of the adapters fits..

i'm also going to recheck the carb gaskets..


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## luckyvision (May 24, 2007)

what about the loose idle screw in the valve? should it be sealed above it? could that be a vac leak?


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## paulr44 (Oct 14, 2008)

If you're a Stihl dealer, perhaps you also deal with other brands. We deal with two distributors that carry Walbro, one of them has the WYL-26-1 in stock. Dealer cost is $24.00. Many distributors carry Walbro, or you can search for a local dist. http://wem.walbro.com/distributors/service/distributors.asp

I have the Stihl kit too, being a Stihl dealer. Made a CC press/vac test plate today to fit an old Wacker rammer with the Wacker WM80 engine. Was missing piece of cyl. base gasket, and completely slimed, wouldn't idle couldn't spray-test. Made a plate to fit RedMax EBZ blowers. You have to improvise all the time!

Good luck, Lucky.


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