I recently had problems with two different Zama carbs running Gas/Glow. The diaphragms are apparently not resistant to the fuel mix, and will swell up. I believe I have run every different type of diaphragm material they make in the Walbro carbs with no problems on Gas/Glow, but watch out for these problems with the Zamas. Keith at BME told me that he had run Zama carbs on glow fuel in the past without problems, but perhaps they have changed the material in their diaphragms.

It was a bit strange when I had the problems. The first day, the engine ran perfect, and when done I ran it dry like I always do and injected after run oil. The next day, it was like all of a sudden the carb was all out of adjustment, and then, while trying to adjust it, it finally got to where it just wouldn't richen enough. After some trouble shooting I found the swelled diaphragm. I tried another Zama carb with a new diaphragm, and the same thing happened. Could be a bear to trouble shoot for someone not really familiar and comfortable with carb work....

AV8TOR

OK,
Then can you substitute a diaphram that will work on the Zama?

If you have a problem with Zama, better substitute the whole carb. If I remember right in this engine Poulan used C1U with 7 mm venturi. So you can easy replace it with relevant Walbro, 7 or 9mm. It will cost not much more than the ZAMA kit.

Will the engine run on pure gasoline? Do you have to keep power going to the glow plug at all times? NOOB...sorry[&:]

EDIT:
With running the glow plug, you need no magneto. Do you need the flywheel?

No flywheel needed; the propeller acts as a flywheel. Pure gas will need an ignition system of some sort. Gas/Glow does not, and with the proper fuel mix it does not need glow power after starting.

AV8TOR

for the gas/glow mix.....is it that easy? I mean, just take some SIG airplane fuel and mix it with gasoline?

does the engine put out the same amount of power??? better or worse???? I have a g-23 on a funtana, that could use less weight....

gould you het another picture of the bottom of the adapter?
i have just finished mine.
but i couldent make mine out of an old spark plug, i had to machine the whole thing including threads on the lathe.
but the end result is the glow plug is about 1/4" from the bottom of the adapter, is this too much?

shaun..........hi chrispy

Simply bevel the bottom of the adapter.

This will open it up and give you proper ignition.

Ralph

Everything you wanted to know about running your gas engine on a mixture of glow fuel and gasoline (Gas/Glow) and throwing away your ignition system right here: http://www.rcuniverse.com/forum/m_12...page_81/tm.htm

AV8TOR

Hi
Many thanks for your time Rysium.
I send your conversion thread to friends who like to start converting.
They see my Weedeater old model ( black plastic crankcase back with four bolts) flying in a show and are interested.
I am from Argentina and this weedeater is sold for 140 U$S ( yes 140 U$S) in Wall Mart and others.
But good glow fuel cost more than 16U$S a gallon ( 5% nitro). Gas is 2 U$S a gallon
You helped me a lot and to take away conversion taboo from my friends.
Actually my Weedeater have 50 hours of flying time logged and the only problems are dirty fuel (change filters and clean carb) and replace one spark plug and ocasionally clean plug for carbon deposits, I use rope starter never a problem, enlarge throath of carb to near 3/8" and use standard filter and choke assembly, very convenient in my dirty airport.
Must change 12 props because dont survive destructive test in the 50 hours of flight
Good landings
Jose

I went over to the local small engine guys shop and picked up a Poulan 25cc weedeater engine(20$) and followed these instructions.

Bought the muffler and prop adapter from Wacker Engines and a Zenoah velocity stack and glow plug adapter and 16x8 Master Airscrew prop(atomic hobbies).

I cut off the excess parts off the engine and used a holesaw to cut out the flywheel center. I trued up the remaining hub to a couple thousandths with a dial indicator. I made an aluminum mounting plate with cable crimp standoffs and 6/32 machine screws.

I used 1/3 15/20glow and 2/3 87oct gas and I am getting about 7400rpm with a reliable idle at around 2000rpm on a 16-8 prop. I might be able to idle it down a little more maybe 1800 or so but it gets pretty rough without glow power that slow. This engine had been used very little before somebody backed over the wand with a car so it might need to break in a bit yet.. I tried a few different glow plugs and ended up with a tower hobbies r/c plug that worked the best. I haven't tried many plugs mainly old idle bar plugs(they didn't work well). Sometime I will have to get a 4stroke plug to try.

Ran it a little more and idled it down to 1800rpm. It will transition to 7000rpm pretty quick and then it will slowly climb up to about 7400rpm. I will need to screw around with it some more.

It weighs 44oz. with the prop on it ready to fly. I am thinking of putting it on my Dragon Lady but it might be a little much for it. The Magnum .91rfs I have for it weighs considerably less and turns a 14-6 at 10000+. Maybe a little bigger plane is in my future(maybe a BIG oldtimer??).

What do you guys think??