Rainman-ACRF

Hi,

Sometime back my ZDZ 40 stopped running (after only a couple of flights I might add) and despite several attempts to get it to start I gave up and the model has lived at the back of my workshop for the last 8 months.

Yesterday I finally decided to have another go at breath life into, and after checking all the basic things it appears that no fuel is being drawn into the carb - I can see an air-bubble in the fuel line going into the carb which won't budge no matter how much I flip it - choked, throttle open, everything. I've checked the tank to make sure I have no obstructions and the clunk is still attached and thats all fine.

So, I guess there is a blockage somewhere in the WALBRO carb. I've just removed the carb from the engine and removed the diaphram, but from here on I'm stumped.

Anything I should be looking for? What should I check and how do I check/remedy it ?

Thanks in advance.

Phil

AirTech

My Feedback: (18)

I have a somewhat similar problem with my 40RV-L. Mine is older so it has a Bing carb that's very hard to prime and it will not hold idle speed anymore. In my case I believe the diaphragm is defective (stretched, to stiff, dry rotted, or punctured). I have not taken mine apart yet, I will shortly.

Check the diaphragm for these problems, and purchase a carburetor re-build kit from RCS. By the way, do you know what model Walbro you have on your 40? I will like to swap my Bing for a Walbro and need the carb model number.

ScottK

My Feedback: (9)

Hey fellows...

[link]http://www.rcuniverse.com/forum/m_113649/tm.htm[/link]

AirTech

My Feedback: (18)

Thanks for the heads up..........

Rainman-ACRF

Yeah, well I just read that info in that link .... so I'm still waiting for a "rep" to answer my question. Please, a little help and guidance would be much appreciated?

AirTech

My Feedback: (18)

Rainman,

I finally figured out the problem with the 40RV. I forgot to mention that I was running a brand new PCM receiver and a JR 9303 transmitter on that airplane. The fact of the matter was that the throttle servo was not only reversed, also the throws end points were way off. I don't know if you are aware or not, when you remove the mechanical stop for the idle adjustment of the throttle butterfly the butterfly will be able to rotate a full 180 degrees. So in my case the throttle was closing on the opposite side of normal, and in the RCS website http://www.rcshowcase.com/html/faq.html FAQ section it's very clearly stated "The throttle shaft OPENS the throttle butterfly by turning CCW (while looking down at the shaft)."

After I got that mess straighten out I could prime it 10 to 15 revolutions, choke on, ignition on, and it will fire on the third or fourth flip. Then choke off, two more flips and it will start right away. Idles at 1900 to 2000 RPM's and turns a 20-10 BME prop at 6200.

I will suggest several things in your particular case. First, disconnect the throttle servo and move the throttle arm all the way forward (shaft will move CW) until it stops, at this point the throttle is fully closed. Mark with a felt tip that location in relation to the shaft c-clip. At this time set your throttle stick to full idle and your trim should be set to the full shutdown position. Make sure your radio end point trim adjustment is set to 50% of the total travel (i.e. total travel 150%/2=75% for the JR9303), this depends on the type of radio you are using.

Now move the throttle shaft CCW approximately 90 degrees. This should be your fully open position. Mark that spot with a felt tip pen for future reference. Connect your servo arm back up and make sure that it matches close to your first mark. If not make a mechanical adjustment of the linkage until it does. After that move the servo with the transmitter all the way to full throttle and adjust the high endpoint by the radio trim until it does.

Now with the throttle fully opened and the choke engaged prime it 10 to 20 flips (don’t worry it wont flood). Take your throttle to idle, make sure the trim is set to fast idle and turn the ignition switch on. Flip it until it fires and after it does remove the choke and flip it again, it should start. Set your idle and full throtle RPM's with the help of a tachometer to fine tune the end points.

If you are still having problems, try closing the choke and covering the intake with a finger while priming it at least 20 flips (a helping hand come handy at this time). Try the same starting sequence and if it fires and then it dies (while at fast idle) you must have a bad carburetor pump. If it doesn’t fire at all, then you have a defective ignition, a bad wire, or plug, or your Hall sensor timing position is not good. (See the “How is the ignition Sensor adjusted on a ZDZ® engine? Section on the FAQ section of the RCS website.

Please let me know if this helps you at all because I am trying to compile information to help others in resolving problems with these amazing little gas engines. Good luck and happy flying.

Rainman-ACRF

My engine has been working fine and I know how to start it and operate it. I've diagnosed my fault as fuel starvation and I need some specific info on stripping and maintaining the carb supplied with it. I would have thought there would be a wealth of information out there but I don't seem to be able to find any.

To be frank, I'm less than satisfied with the support offered by the so called official techs that have all but ignored this post and this ZDZ is about to get ebay'ed for a DA or something. I'm done with ZDZ.

AirTech

My Feedback: (18)

Rainman,

Both Walbros and Bing carbs are very similar and if you purchase tha correct rebuild kit should not have any problem installing one. I don't think you will find instructions it to hpw rebuild any of these carbs, so if you you do try it you are mostly on your own.

I suggest you try at least rebuilding the carb, and if that doesn't work or you feel that rebuilding id outside your mechanical abilities, you can always get a new carb for around $50 bucks. In my experience most high performance gas engines are a little sensitive and require a lot of TLC. 3W engines are some of the most powerfull engines I know but they need to be installed and adjusted perfectly or they will give you problems. Don't discard your ZDZ because once these little engines are broken in they are quite a powerhouse for their weight. If you are interested in just an engine for all around sport flying buy a Brilleli, SPE, or Brison. These engines are easy to start, no fuzz adjustments and fairly good service support, although they will not match a ZDZ power output.

Zeeb

My Feedback: (41)

At the risk of being equally frank, this forum is covered by RCS who is the USA distributor for ZDZ and thus any opinions/thoughts/recommendations they might offer probably wouldn't do you any good, unless you were willing to pay for shipping stuff across the "pond". The do this support forum as time permits and while there's not always a quick answer from them here, the normal support channels for RCS of e-mail or better yet the telephone, are answered very quickly.

Second, your questions/problem would have been better addressed in the gas engine forum before deciding that it was specifically a ZDZ problem and the US importer owed you some free advice. Who did you buy the engine from? Who's the importer/rep in the UK for ZDZ? Did you try ZDZ directly?

You wanna get a DA-50 instead? Go for it, while DA's service is second to none the 50's do have some of their own issues....

ZDZ's are great engines and the throttle response of the rotary valve intake cannot be duplicated by a reed valve intake engine. Power to weight ratios are always a subject of discussion, but I think you'll find ZDZ is consistently one of the best as AirTech has mentioned.

Sorry you're having troubles, but slamming someone who owes you nothing is not the way to get any help...

dubd

airtech, 6200 rpm seems low. I have a ZDZ40 and I am getting 6200RPM and my Hangar-9 P-47 is a dog in the air. I called RCS and was told I should be getting 7000 rpm with my Xoar 20x10 prop. Have you flown the plane with the ZDZ40 yet?

Rainman-ACRF

Hey, I came here looking for some carb advise as used in conjunction with a ZDZ product and all the perculiarities that may (or may not) come with it. Someone pointing me in the direction of some kind (any kind) of resource so that I could do this myself would have been useful nay simple enough for someone with the experience of these things, as this is something I'm fairly new to.

Sorry, but the impression I had after someone quite kurtly posted some link to an item of dictum left me with the impression that this was some kind of official ZDZ support forum and woe-betide any kind soul that might offer advise (as someone other than an "official tech" did kindly offer). It would have taken someone no effort at all to just guide me in the right direction, however misguided I might have been in coming here in the first place. So you say I should have picked up the phone .... are you suggesting if someone employs a number of contact options it's ok to ignore some and not others? Thats kinda what you're implying.

Like it or not, whoever supports ZDZ is an ambassedor for the brand, wherever it may be. I didn't ask anyone to provide with anything that would cost them anything other than a polite "what you want is that-a-way ---> ".

I don't care much for your "frank" reply, because you're now slamming me when all I wanted was a little advise, got next to nothing in three months, and somehow this is my fault. I don't know who you are, but if you're anything to do with ZDZ then you just signed a blank cheque for an alternative brand. Unfortunately, RCU isn't just a US resource, it's a global resource and hence a lot of ppl from the UK come here, but no one expects such short efforts in a little help wherever they're from - a forum link, anything would have been nice but thats how it is I'm sorry I caused everyone so much trouble. Jeez.

nonstoprc

My Feedback: (90)

It might be a good idea to check the diaphragm in the carb. By that I mean how it was installed. If the flat surface is facing the cover, then you will not get much fuel drawn. The other potential cause is that the pulse hole is blocked somehow.

AirTech

My Feedback: (18)

dubd, 6200 RPMs are about as much as you are going to get out of a BME 20X10 and I doubt very much a Xoar will do much better, definetly not 7000 RPMs. My Evolution 58 turns a 22X10 Pro-Zinger at 6900, and I doubt it will do better than 7200 with a Bolly or 22X10 carbon graphite Mejslik. Remember, engine distribuitors and manufacturers are extremely over optimistic in their performance claims.

By the way I have flown the ZDZ 40 on a 25%, 17.5 Lbs Extra 300S with excellent results, It barely hovers at 75% power, but it will go vertical at full power. Please be aware that this plane will fly and balance better (I have 8 ounces of lead in the nose) with a 50cc engine, and this is an aerobatic plane with problably better wing loading than your warbird. It's always a good idea to overpower your wabirds to compensate for the higher wing loadings.