Hello All,

I was wondering if anyone could post tips on the running and setup of a ZDZ-40 engine. Last year, I was the RC pilot for my University’s UAV program, and we used an aircraft with a ZDZ-40 engine. It was always very hard to start. Once we could get it running, it seemed to run OK, but I was never really comfortable with the engine. I have a feeling that the reason for the hard starting was probably an incorrectly set carburator.

Now I’ve graduated, and the project has asked me to come back and act as the pilot/advisor this year. Now that I’m not concentrating on deliverables, and passing grades, I have more time to figure out how to set up the carb properly, and get the engine running reliably.

I have lots of nitro experience running both two and four stroke engines, but this is my first experience with a larger gas engine.

Could anyone with ZDZ-40 engine experience give me some tips. In particular, I’m looking for the following:

Starting procedure, both hot, and cold.
Carb setup procedure.
Typical props used, and the RPMs
Anything else I should watch for on this engine.

Thanks in advance,

Tom

try this [link]http://www.rcuniverse.com/forum/fb.asp?m=1353135&key=first%2Cstart%2Cflip[/link]

Thanks for the link. I will keep all of that stuff in mind.

What is the carb setting technique for these engines? Is it similar to a glow engine? i.e. set high speed needle for clean full throttle first. Then set low speed idle for reliable idle and good transition from idle to WOT?

Also, what are the signs of rich and lean running, particularly on the low speed needle.

I believe we're using a 20x10 Zinger Prop. Any guesses of what full throttle RPM would be?

Thanks again,

Tom

Hello Tom
As a newcomer to the gas engine section I had a pretty hard time starting my new ZDZ 80 twin. It never wanted to start and I already thought there would be some carb problems. Now, after having had some instructions by my local dealer the engine starts after some few flips. What you should never do is priming the engine like we are used to do it on glow engines. The carb/pump (Walbro or Bing) sucks fuel/gas in the carb by itself and more priming is definitely heading for troubles!
Starting procedure:
- close choke, full throttle, ignition on
- turn till it 'plops'
- throttle to lowest position
- open choke
- turn and it will run
Best regards, Daniel
Sorry for my English, I am Swiss German

Diaphragm carbs on gassers are not set the same way as 2-needle glow carbs. The low needle on a gasser effects the carb mixture from idle to full throttle. The high needle effects the carb mixture from about half throttle to full throttle. With a gasser, you set the low needle first for good idle and responsive acceleration to about one third throttle when you snap the throttle open from idle quickly. Once you have the low needle set, adjust the high needle to max rpm with a tach, and back the needle open a little to make sure the mixture is slightly rich (down 100 rpm from peak). Test fly. If it sags or slows down on vertical lines, richen the high needle about 1/8th turn and try again.

From experience. Run at least a gallon of fuel before first flight as the engines are tight as they dont idle very slow for long periods when new.This may prevent flameouts mostly on slow idle. Second Fill the tiny hole in the butterfly with solder as to to get a good choke on the motor. . They like to start wet but not flodded. If you have it on a test stand squirt a little fuel through the carby with the throttle fully open flip the prop then switch on the ignition. If if fires straight away you know its wet enough.My procedure is to close the choke and flip about 10 times with the throttle open, close the throttle to about 1/4 switch ignition on and flip till engine pops. Then choke of.. Remember that if you wait to long the auto ignition cut of in the modual wont allow any spark which is an important safety feature of the of the ignition modual to prevent accidental starting of the engine .If not sure switch of and on again.. My hi and low needles were set at about 1 turn from there you should be able to to get a good stable idle and transition. Every motor has its own favourite starting procedure.youre task is to find what youres is.