KT 17 Walbro Carburator ??

[Brockport Bill 1,661]

I have a C175h Series 2 engine with a Walbro carb # 5205334 / WHG 471359. I have removed carb and doing carb rebuild with carb kit 25-757-11-S. I am not the original owner so do not know what has been done with the carb previously?????? The Walbro carb I removed has a needle with no spring or clip of any kind --- and sits freely in the valve jet hole below the float. However, the carb replacement kit provided two different replacement style needles ( see photo )  - each slightly different design from each other -- one has a clip on top of the needle ---- and the other has a spring type attached on the top of the needle. -------------- How is the new needle installed? Does it sit freely in the needle valve hole and works by gravity as the prior un-attached needle ?????? Or - is the clip at top of the spring "clipped" from underneath the float arm tab so it is mechanically "lifted" with the float when float moves up and down?? ----------------- Second issue????? ( see photos ) The Walbro has "dome shaped caps" in two locations on the carb housing. The rebuild kit provides new "dome shaped caps" -- suggesting the old caps should be removed and replaced? Should the old caps be removed and replaced?  I assume there is a port or jet underneath that maybe should be cleaned -- but I am not a carb expert so dk? If the dome caps should be replaced - how are they removed? I played around the old caps with a dental tool and they appear a major challenge if I attempt to remove? I'd appreciate any insights on the two issues - the needle install, and the dome caps --thanks!!!

[ebinmaine 67,424]

I can't speak for the needle and seat issue having no experience with a Walbro carb. 

 

VERY IMPORTANT: 

Have you carefully verified that the throttle shaft is reasonably tight in the bore both top and  bottom? 

 

 

The "dome shaped caps" appear to be what I call a Welch plug or on a liquid cooled engine,  a freeze plug. 

Kohler carbs have one as well. 

I do not usually remove the one from a Kohler but that one sets at an angle and is easily sprayed behind from two directions.  

 

The ones on that Walbro carb,  I would remove. They're at two different levels and ports and I don't know what's behind them.  

To remove them you'll need a small drill. 

Great care MUST be used not to penetrate too far in to avoid damaging the internals.  

 

After cleaning the ports behind the plugs they can be reinstalled using a correct sized punch. 

They set in place "bowed side out" and the punch creates the dimple that holds them in.  

That too, can be a delicate touch.  

I've seen videos about that.  

 

 

[Handy Don 12,213]

The coiled spring clip on top of the needle valve serves two purposes.

First, it “buffers” the action of the valve closing as the float lifts on the rising fuel level in the in the carb bowl. The goal of that valve is to govern the height of the fuel in the bowl so that that fuel flows consistently into the rest of the carb. The spring lets the fuel level vary very slightly.

Second, the spring physically links the needle to the float. While fuel is pumped into and fills the bowl the needle closes and can “stick” closed when there is low fuel pressure from the source. With the spring linking the needle to the float, as the float descends due to  the engine drawing fuel from the bowl, the weight of the float will help pull the needle open. 

 

The non-coiled spring serves only the second purpose.

 

Why the different ones are used in different carbs remains a mystery to me!

[Brockport Bill 1,661]

1 hour ago, Handy Don said:

The coiled spring clip on top of the needle valve serves two purposes.

First, it “buffers” the action of the valve closing as the float lifts on the rising fuel level in the in the carb bowl. The goal of that valve is to govern the height of the fuel in the bowl so that that fuel flows consistently into the rest of the carb. The spring lets the fuel level vary very slightly.

Second, the spring physically links the needle to the float. While fuel is pumped into and fills the bowl the needle closes and can “stick” closed when there is low fuel pressure from the source. With the spring linking the needle to the float, as the float descends due to  the engine drawing fuel from the bowl, the weight of the float will help pull the needle open. 

 

The non-coiled spring serves only the second purpose.

 

Why the different ones are used in different carbs remains a mystery to me!

thanks for specifics don -- so just to be clear, the clip at top of needle is attached to float, rather than just sitting unattached under the float? 

[Brockport Bill 1,661]

6 hours ago, ebinmaine said:

I can't speak for the needle and seat issue having no experience with a Walbro carb. 

 

VERY IMPORTANT: 

Have you carefully verified that the throttle shaft is reasonably tight in the bore both top and  bottom? 

 

 

The "dome shaped caps" appear to be what I call a Welch plug or on a liquid cooled engine,  a freeze plug. 

Kohler carbs have one as well. 

I do not usually remove the one from a Kohler but that one sets at an angle and is easily sprayed behind from two directions.  

 

The ones on that Walbro carb,  I would remove. They're at two different levels and ports and I don't know what's behind them.  

To remove them you'll need a small drill. 

Great care MUST be used not to penetrate too far in to avoid damaging the internals.  

 

After cleaning the ports behind the plugs they can be reinstalled using a correct sized punch. 

They set in place "bowed side out" and the punch creates the dimple that holds them in.  

That too, can be a delicate touch.  

I've seen videos about that.  

 

 

thanks Eric for detailed description --- last night after posting, i watched a few YouTubes -- Walbro actually says they offer tool kit for removal of the "freeze plugs / Welch plugs" -- with punch technique without drilling - - however, because the plugs were engineered by mfg to be for federal air regulations the plugs are not intended to be removed but rather the Walbro tool kit for the plugs is only available to be sold to dealers -- not consumers. I believe i adequately cleaned the inside of carb -- first spray, then ultrasound machine, then compressed air - - so hopeful any cleaning necessary is thorough -- i am assuming what's behind the plugs don't have to be adjusted because the mfg wouldnt have made them "permanent" ---- my initial priority was for carb to be clean -- and only then adjust those areas accessable -- so now i will decide if removing the plugs is critical - many thanks ! Bill

[Handy Don 12,213]

6 hours ago, Brockport Bill said:

thanks for specifics don -- so just to be clear, the clip at top of needle is attached to float, rather than just sitting unattached under the float? 

Yes, both types of springs capture the little tab on the float so that the lowering float can pull open the valve.