frankeldan

I'm having problems getting my idle down low on my G38. The throttle arm is all the way closed and I've played with the low needle setting to no avail.

Could it be the needle valve lever assembly in the carb that needs adjusting ?


Thanks,

Dan

Jburry

is the throttle arm hitting the idle stop screw? If it is, remove the idle stop screw completely. A fully closed throttle will shut the engine down.

If it won't, there'd have to be an air leak between the carb and the engine, but then I'd expect the engine to run poorly. Look down the carb throat at the throttle butterfly. It should be touching the walls all the way 'round when it's closed. Any space at all, and it's not closed.

J

frankeldan

Thanks for the reply:



is the throttle arm hitting the idle stop screw? If it is, remove the idle stop screw completely. A fully closed throttle will shut the engine down.


The idle stop screw is completely out.

I
f it won't, there'd have to be an air leak between the carb and the engine, but then I'd expect the engine to run poorly. Look down the carb throat at the throttle butterfly. It should be touching the walls all the way 'round when it's closed. Any space at all, and it's not closed.

The engine runs great at high throttle and midrange is good. I took the butterfly out to examine it and it seemed to be seating fine against the walls. Like you said.. It seems to be getting too much air at the fully closed position.


Regards,

Dan

Big_Bird

My Feedback: (1)

If the throttle return spring had been removed at some time then there is a good chance that vibration has caused end to end wear on the throttle butterfly. This wear causes excess air leakage around the butterfly. Also if the butterfly is not aligned properly, when the throttle is closed, excess air flow will occur. Excess airflow causes high minimum idle.

If you should need to replace the butterfly then replace the shaft with a new one. The screw that holds the butterfly on is peened to prevent it from backing out. Often times when the screw is removed, due to the small diameter of the shaft, one side of the shaft will split where the screw goes through. When you put a new screw in the new shaft. use red Loctite to secure it.

frankeldan

Big_bird,

Thanks for the reply. My first thought was the butterfly too. That's why I removed it to inspect it. I'll go to my local chainsaw dealer guys to see if I can get a new one. If I need to replace the whole carb what is the model I need? that's worse case.



Dan

Jburry

If you intend to replace the carb, take the one you have with you. There is a part number molded into it, and they can find a suitable replacement based on that.

J

Big_Bird

My Feedback: (1)

Dan I no longer own a G-38 and I don't know what the number is. It should be on the carb with letters like WTA or HDA plus a number. Ralph Cunningham is an expert on Walbro carbs and Zenoah engines. He can sell you a carb, parts, rebuild your carb or give you free advice. You can find him here: http://www.rcignitions.com/

frankeldan

Thanks for all the info guys. It's mounted in my KMP Pitts.. This is the plane that MAN did the article on last year. I mounted this engine up and have not taken it up since the idle was high. I forgot what I tached it at in the fall.. all I know is this thing would need to be brought in dead stick if I took off.

Dan

Dr1Driver

You mentioned you had the butterfly out. Has it been out previously? If so, it may have been reinstalled backwards. There are three vent holes in the carb barrel that must be covered or uncovered (I don't remember which) at idle.

Dr.1

frankeldan

Well guys.. I was at the WRAM show yesterday and B&B specialties were there. I took the easy way out and bought a brand new carb from them. They also suggested it may be a faulty butterfly. Since the original carb has the idle screw tab broken off I decided to buy new. Thanks for all the help.

Dan

ljones5000

My Feedback: (2)

I have a G38 which came without a choke on the carb. I wanted a choke and replaced the carb with a WT-338-1 and it works fine on the G38. I bought the carb from VE Petersen Company. They have a website, look them up.

Edit: Oops, I didn't read far enough to see you already bought a carb from B&B. You won't go wrong with B&B, they're top-notch and I know whatever they recommended for your G38 will be good.

electricpaps

Hi guys,

I have the same problem on my FTL 45 (GF 45i clone) - High idle. I've tried just about everything to no avail yet. I think my butterfly valve is fine. But I do have a shakey teflon carb adaptor and an air leak looks possible.

It would explain my symptoms :

High lean idle
Can get a low idle if L needle adjusted very very rich, but then the engine runs too rich in the air.

Happy flying
Paul