Hi,

This is my first experience with a gasser. I have a G26 in a 1/4 scale Sopwith Pup and I fired it up for the first time today.

I was never able to start it by flipping it by hand although almost every time, it did fire. It started with a starter but died easily. I had to start it at about 1/4 throttle but it ran pretty fast. (I did not have a tach with me at the time.) Throttling down just made it die. When I throttled up, the rpm would increase until about 3/4 throttle and then it would start to mush at bit. The rpm would roll off but it kept running. Throttling back down would have to be done slowly or it would die.

The idle and high mixture screws are per the factory settings but since I am new at this, I don't know how to adjust them.

Any help would be appreciated.

Thanks

Chevelle,

I own several of these awesome engines... they run better than my DA and 3W. Here's a few tips:

Not all engines run perfect out of the box... I have had to tinker with a few of my recent ones. ..
Before I get into it - did you remove the carb air horn or carb at all - or did you rotate the carb 90* to line up your linkage?? I am assuming you did not at this point as the engine would usually not run at all , but often, removing the carb to install the "free" air horn Zenoah puts in the box causes the carb base gasket to leak. In addition, every engine I have bought so far had the wrong screws (too long) in the air horn kit which would not let the gasket seat fully creating vacuum leaks.. I had the grind them 1/8 of an inch to make them work.

Also - remove the large silver idle stop screw, it is not needed. Use the radio/servo trim to close the throttle plate fully.

If the carb is OK, then here's my advise..

1> Don't waste your time hand or spring starting. A cheap electric starter turns this engine very easily. Unless you know exactly how to start a magneto engine by hand, it will never start. More often than not, the engine will kick and bite your hand too, so for safety sake alone, use the electric starter.

2> Your needle settings are too lean, they usually are out of the box. Try this - close both needles and open to factory spec + 1/2 turn. Apply the choke, and normal idle throttle position (barely open) and use the starter to motor over the engine until it "pops".. if it runs, that is OK, but eventually it will load up and die. Most likely it will only pop and then immediately die. Usually the engine only continues to run at full choke if the carb gasket is leaking or its very cold outside.

3> After the engine quits open the choke, and move the trottle trim a notch or two (a bit past idle) motor the engine over again and it should start and run. If it starts and runs, let it run without touching the throttle for about 30 sec to 1 min. If it runs OK but the exhaust appears real smoky - its too rich, you will need to lean the low mixture screw 1/4 turn at a time. If it does not idle, increase the low speed needle 1/4 turn until it does. Continue to do this until it runs. You want at least a rough rich running engine at this point.

4> Once you get the engine to idle, advance the throttle slowly.. the engine should pick up speed. If it does not, you need to open the high speed throttle needle 1/4 turn at a time until it runs well at high throttle. Have someone holding the plane while you are doing this.. !

5> Once you get a basic rich running idle, and can achieve a high RPM, you can tune for best performance. I do it by ear as I am very experienced, but a tach is helpful. You want a smoothe transition from low throttle to high throttle (i.e. no stumbling, burbling sound, etc) and a very strong steady high RPM reading. Usually playing with both needles is required, but is very easy on this engine. Have someone who has one help.. it really is easy.

6> If after this you cannot get the engine to run well, loosen the 2 carb screws and re-tighten (don't overtighten), check your fuel lines and tank for leaks, and make sure your tubing is of sufficient size to supply the larger engine.

by now you should have a very nice running setup..

DP

What a great reply! Thanks. I actually suspect a gasket leak. I will take the carb off tonight and remount it and also check to see if the screws are seating before the carb does.

I'll give the rest of your advise a try tomorrow. Sounds to me like you have it pegged. Thanks and I'll let you know how it turns out.

OK. Almost got it working. It idles nice, moves up nice, and run nice at full throttle. I tightened down the carb base and the carb and also found that the throttle was turning the wrong way which is why (I think) it wouldn't idle.

One more issue. I can't seem to get it to shut off using the transmitter's low ilde button. It looks like the throttle leaf is all the way closed and it is still running. I know there is a taper on the leaf and it may be mounted the wrong way. Is there anyway to tell by looking at it through the air intake?

Below is the exploded view from the Walbro website and it looks like my leaf is the same way as in the picture. The dimple slit is up towards the top carb housing.

Thanks.

With the carb mounted on the engine, look into the venturi...If you can see the head of the screw with the throttle closed it's opening the wrong way....
the disc can be slightly out of position on the shaft...With the carb off the engine loosen the screw slightly and make sure the dimple is touching the shaft..You can wiggle the disc and shaft and get it to close completely, then tighten the screw..You should not be able to see any light around the disc when it's aligned correctly...The shaft is brass so don't try to break the screw when tightening it...Use a drop of Loctite on the screw if possible..You don't want the screw to come loose and go through the engine, it will destroy the cylinder and piston....

Are you sure you have enough throw on your servo to close the throttle? I have not seen what you are describing happen. As RCIGN1 stated, look at the butterfly (plate), but my guess is that is correct unless someone rebuilt the carb and got it wrong. ... is this a new engine or used / rebuilt??

DP

All problems solved!!! It was a combination of things including rotating the butterfly the wrong way and having it mounted on the shaft incorrectly. Upon more careful inspection, daylight could be seen at the edges of the butterfly allowing enough air to pass through even when it was fully closed.

Engine hand starts fine, idles fine, and runs up fine, thanks to the suggestions here and from my fellow club members.

This week I'll get used to ground handling and over the weekend, hopefully, I'll put it in the air!

Thanks again.