cymaz

I was running up my Zenoah G38 today and it was not really on song. It is fitted with a wt338 carb from Walbro. I currently use 32:1 fuel.
The problem is that there is a lot of oil coming from the exhaust. I have fully synthetic high performance 2t oil.

Is 32:1 fuel/oil ratio the correct mix, I use that because that what it says in the instructions.
I have fitted a trumpet to the carb and I notice that there is fuel pooling in it at idle to quarter throttle. The mid range richness has gone however.
Can I reduce the oil content and will that harm the motor ? Should I remove the trumpet?

I know RCU will see me right
Thanks

Scota4570

I would not. You might try regular oil. I have notticed that the synthetic types are messier. Pennsoil 2-stroke, and many others are very good. I run my G-38 on whatever oil I have handy at 32:1. In fact I run every thing I have at 32:1. It could be Pennsoil, fancy synthetic, or even hardware store house brand. At 32:1 it does not matter. You may be able to go with less oil, call Zenoah. I don't see the point though. 2-stroke engines are messy. If you want squeaky clean go electric.

The trumpet has nothing to do with it. It will help keep fuel from spraying back ot of the carb. Have you ajusted the needle valves? IF not, get help to optimize the settings. If it is too rich it will spit oil.

flyinwalenda

My Feedback: (5)

I run 40:1 in my Zenoah engines and others(except for the 10cc) using synthetic oil (Klotz) . Usually have a few specks of residue on the plane after flying.
I would suspect it needs some tuning if there us fuel pooling in the carb. Have you rebuilt the carb ?

cymaz

It's a brand new carb. Never taken it to bits-(no intention to take it to bits either).
I could try 40:1 it's an old engine.
if I take the trumpet off will the pooling of fuel just be blown away?

flyinwalenda

My Feedback: (5)

Have you adjusted the low and high speed needles and set them correctly for your conditions?

cymaz

Yes, it's just the oil residue I'm worried about and the fuel sitting in the mouth of the trumpet. By the way what has every body else set the needles to. I have no reference apart from what I work with. The zenoah instruction seem very rich.

RBean

With the side carb such as on the G-38, some fuel will pool or spit out the carb at idle and low rpm. I am told this is normal and you can't do much about it. My G-38 does the same thing. So do two others at the club. I use Stihl 2cycle oil 32 to1. It has been running this way for years.

cymaz

Any need for the stack then?

captinjohn

If it is a old G38 the Hi speed Mixture needle can be as little as 1/4 turn out. I was told by a real good Zenoah man. I guess the carb on that engine was designed that way so people could not lean them out & destroy the engine. It is probably on the rich side & that would create more oil than needed.

cymaz

I changed the carb for a newer wt338

1QwkSport2.5r

Most of the Walbro carbs I use on my various lawn equipment engines are all initially set at 1 turn out on both needles for regular gasoline mix. I use 32:1 mineral oil. My ice auger likes a little nitromethane so I will add 1-2 cups of 10/20 glow fuel to a gallon of gas mix and set the needles to 1.25 turns from seated and adjust from there. I set my carbs up the same as a glow engine; high speed needle peaked, low speed needle set for good transition, and richen high speed needle for 300rpm drop from peak.

Brand of engine doesn't matter much. Gasoline engines really can be run on 50:1 if you use a high quality oil. I prefer to use more oil though. It cannot hurt any.

Steve S. Helland

My Feedback: (15)

when my G-38 got tired and STILL idled well with the low needle closed all the way and would not quite reach the high RPMs like she used to I tried everything like you are now. After much conversation with an old timer I was convinced that my engine was sucking air through the seals. I disassembled it and cleaned it all up, replaced just the seals and the gaskets, rebuilt the Walbro carb and it then ran like it was brand new again. Sounds like you are sucking air through an old seal to me. Good luck.

cymaz

Plenty to think about, thanks. I thought that a 18x10 was correct, but now I'm not sure, would a 18x 8 be better?

flyinwalenda

My Feedback: (5)

What type of airframe is it on? I've run 18x10, 18x6-10, and 18x8 props.

cymaz

1/4 scale Gipsy Moth DH60

dreid

My Feedback: (13)

Use a 20 x 8 prop, prefer wood. The plane will like the prop.

cymaz

Would you care to elaborate?

dreid

My Feedback: (13)

The larger diameter prop moves more air at a bit less RPM. A lot of guys flying gassers think you need the rpm's screaming to get the plane to fly. I prefer wood props in case of a prop strike, you sacrifice the prop instead of the crank.

rt3232

My Feedback: (6)

+1 on the wood, and the seals I have found (xoar) works the best for me. 18 X 8 or 6, and 18 X10 also 20 X 6 flying an 18 + pound Weeks bipe, and becouse I can't stand the smell of our pump gas I am using 100 ave gas and Klutz syn at 40 : 1 and I have all ways had a little spitting at idle, also a short stack cut at a 45.

cheers Bob T
AMA13377

Gizmo-RCU

My Feedback: (27)

Yes on the seals, just replaced them on mine and resealed the crank case, helped a bunch!
Yes on the 18x10 prop, mine loves it, with the wood prop.
I have just over a hundred flights on my Giant Big Stick W/G-38 for power, good combo for my flying. I use Husquvarna Syn. 50 to 1 with non-ethanol preminium in my planes and chainsaws. No problems and they run well!



3

ccostant

My Feedback: (38)

Just one more data point for you. I've run my G38 for the last 5 years in a Hangar 9 P-47, probably no less than 300 flights total, with either Klotz or Pennzoil at 32:1 mix. I've used a Mejzlik 18x10 the entire time. Motor still runs great and leaves just a little trail of residue from the muffler exhaust, fairly light in color. High end RPM on the ground is tuned to ~6600 and low end RPM ~1600.

Beavis

My Feedback: (19)

What kind of gas do you use?

Thanks in advance,

cymaz

Is it a big job replacing the engine seals..I see from here the crank should come away quite easily. Do I need any special tools?

cymaz

Took the carb off today. No crud in the filter but I did find a small tear in the gasket that sits between the nylon block and the carb....

rt3232

My Feedback: (6)

cymaz

waaaaay back a frind of mine that worked in an automatic xmission shop gave me a tube of "loc-tight" gell and his recomendation was a light smeer on each side of gaskets and a good smeer on metal to metal joints for all seals and I would eliminate any joint seal leaking, I have been useing it ever sence and have not had a leak sence.

Will go to the shop this evening and get the number and exact name to post


Cheers Bob T
AMA13377 Corsair Brotherhood #6