Problem with Wt-990 Carb...

[brio]

I just installed a new WT-990 carb and I notice it sticks at full throttle. When I push it to full throttle with my hand and engine off and it clicks and it just sticks there, the spring tension doesn't swing it back. I have to force it, it clicks again and back to neutral position. Is this normal? Or did I get a defective carb? Thanks. It's really dissapointing cuz I was just in the middle of breaking in my new OBR 30.5cc Prostock engine.

 

[GTS 666]

That's not normal for the carb to do that it shouldn't make any noise. I would take your air filter off and check the butterfly in the carb. It operates how much air comes in. It has one small screw in it I would loosen it slighty as the butterfly may not be centered properly in the carb. Don't take the screw out completely with it on motor as it could roll into the motor.

 

[Deluge]

That's not normal for the carb to do that it shouldn't make any noise. I would take your air filter off and check the butterfly in the carb. It operates how much air comes in. It has one small screw in it I would loosen it slighty as the butterfly may not be centered properly in the carb. Don't take the screw out completely with it on motor as it could roll into the motor.

Completely agree.

 

[brio]

Well, it was actually nothing to do with the carb itself. It was the fact that my HY engine cover does not fit the top end of the zenoah engine perfectly. The front edge of the engine cover was sticking out just enough to block the carb from rotating all the way back. I had to shave off some of the front of the engine cover to allow the carb to move all the way to full throttle without resistance. Thanks. You guys helped my to investigate the carb area more which lead to me discovery.

 

[Deluge]

Glad you got it sorted.

 

[brio]

Well, thought I got it sorted but NOT really. Seems the carb is defective. It happened to me again and I removed it from the engine and the throttle shaft IS sticking at full throttle and about 1/8 throttle. Called Walbro and guy said I could send it back and they'll look at it. He said its not warrantied but he'll repair or replace it. It's pretty much new, maybe about 2 & 1/2 tanks thru it and that was break-in.

 

[Deluge]

Is the throttle plate loose or crooked? If it worked before, the throttle plate could've loosened up during the last tank. Also, did you check the needle side of the carb to see if there's anything binding the shaft?

 

[brio]

Well, I checked it out last night and the needle side looked good. What I noticed was that the throttle shaft that runs thru carb was a bit loose because I could push it in and out, very little, but I could not tighten the screw on the side anymore. When compared to my HY carb, the spring on the Walbro that moves the throttle arm from full to idle is very soft and weak. The HY carb spring snaps back quick and strong, not like the Walbro. I don't know. I mailed it back earlier today. Hopefully, they can repair or replace it for me. I guess I could've digged in it myself but it's new and I'm not too familiar with gas carbs. If you were local Deluge, I would've gladly brought it for you to examine.