tdriver

i have an engine that won't properly shut down when the butterfly is 100% closed,
i thought it would be lean somehow but then i read this [link=http://tech.flygsw.org/walbro_tuneup.htm]walbro tuneup[/link] "read special notes- #1" (at the end of page)

where exactly is that hole??

bkdavy

My Feedback: (1)

I believe they're referring to the hole in the Choke valve. That hole allows sufficient air to flow through so the venturi of the carb will draw fuel into the engine. The butterfly is normally referring to the throttle valve, not the choke.

su26

No They are not talking about the choke butterfly. Look inside your carb with the choke open you will see another butterfly.
Thats the one they are talking about.
I have had the same problem.

Tired Old Man

My Feedback: (1)

If you're engine will not shut down using the transmitter the problem will 99.99% of the time have nothing to do with the bleed air hole in the throttle plate. That's a "wive's tale/tribal knowledge" solution.

The real problem will be is one of a couple of places. One will be the user leaving the idel stop screw that came on the carb in place. It serves no purpose in RC and was on the carb because the carb was designed and intended for a yard or wood curring tool. Get rid of it because it's positioning will establish an idle position that no servo in the world can oversome.

The second is improper linkage installation and geometry. How many people ever btother to leeo to verify the throttle plate or choke plates fully clse when they provide oerational input? If the throttle plate does not fully close the engine can't be shut down with the transmitter because that plate establishes the idel position. Open at all is some level of idle.

The third is having the throttle trim tab up to some degree. When the linkage was originally installed it should have been done with that trim tab in the closed position.

Read the newbies to gas engines sticky.

Truckracer

My Feedback: (19)

While TOM is certainly correct regarding several reasons why an engine will not shut down with the throttle closed, there can be other reasons. For example, an air leak anywhere in the engine can cause this. This is usually accompanied by needle setting that have to be richer than what would be considered normal. This could be caused by a bad cylinder base gasket or a leak between the case halves. Another common problem is a warped carb spacer, reed bank housing or anything that can let air in between the engine and the carb. The much beloved DA-50 is one engine that can experience this problem ... by design. Another area to look at is a worn carb body especially if the throttle return spring has been removed. On many carbs the spring helps to center the throttle plate in the bore of the carb ... if removed the throttle plate can wear into the carb body near the shaft allowing extra air to enter the engine around throttle plate where it has worn grooves into the carb body. This condition is usually accompanied with complaints of intermittent idle problems .. either idle speed or mixture, or both. If the carb body is worn, it becomes a throw away item.

There are other things that can cause your problem but those things mentioned so far are the common ones. As TOM said, most commonly it is just an adjustment or installation problem!

tdriver

i checked everything mentioned above but there was no problem,

so i took off the carb and there is a vent hole after all and it is not the choke.


is it an easy task to remove the butterfly and solder the hole,
or will it give me more trouble re-aligning it once finished?


btw, it's an hlic (rcgf 15)

Antique

My Feedback: (4)

The butterfly is not positioned correctly on the throttle shaft..The edges are beveled to completely close...The impression on the valve is there to line up the valve correctly in the venturi...loosen the screw and rotate the valve until the dent on the other side touches the shaft....Loctite the screw when you put it back...

MetallicaJunkie

i remember about a year or so for no good reason i decided to remove the one off my 55, and i had the same problem

Ed

When you look down the Carb at the throttle butterfly when it's closed; are you supposed to see screw heads, or screw threads ?

Truckracer

My Feedback: (19)

If you look at it from the engine side, you will see the head of the screw.

Ed

So .......... If I understand you correctly ; If I removed the Carb, and looked at it from gasket side, I would see a screw head, and if it was mounted in place and I looked down the throat, I would see the screw thread. Is this correct ?

Truckracer

My Feedback: (19)

correct

Ed

Thank you Got it right !