Today my 80 starting making a noise...It sounds like a spark rattle almost, and it wouldn't take the gas. It was pretty hot to the touch too. I tore it apart and couldn't find a thing wrong...I did notice that some of the braiding on the plug wire was rubbed away where it contacts the cowl..But the bearings are good, no worn places on the piston and cylinder, no foreign objects in there either... Think the ignition is causing this dilema?

What gas are you using?

93 octane super unleaded, poulan 2 stroke synthetic oil...

I bought my first DA-50, and it runs great but i have always wondered about the zdz 80 has it the power they claim to have and besides your problem are you happy with it, just wondering as it looks like a real nice engine

Sounds like it was building heat, and leading to pre-ignition. The piston was so hot the fuel mix was vaporizing in the crank case. You must know your way around engines some to recognise a problem developing. The next sound you would have heard was a piston seizing. Poulan to my knowledge uses Opti2 and remarkets it. Opti2 is one of the first if not the first to design synthetic oils. Still in business after 30 years so they probably know what they are doing by now.
Solutions would be, Smaller prop, try some fresh gas from a different source, back the timing off a couple degrees, tune the high a bit ritcher. It's summer and you should expect quite a bit of performance loss with air density being thin.

i HAVE BEEN REALLY HAPPY WITH THE ENGINE. I picked it up thru France about 8 years ago for 350 bucks brand new.. I put new bearings in it last year .. U mentioned about fresh fuel, when I tore it down last nite, the piston had a huge build up of what looked like varnish and it had an old gas smell...I think the gallon I currently have mixed is about a month old....I do have this engine now in a new sukhoi, not sure if it's overheating from the cowling or not. I have the bottom open around the pitts muffler and the head and I also cut out all of those louvers on the cowl....

A friend of mine broke a head bolt on his da-100 and sent it back to be replaced, they called him to ask him what he uses for fuel as his engine was so clean, like no other, i have learned so much from these guys that have been flying da- for years, they both use chevron with that tecron in it and so that is what i use, i always use only one type of oil or gas or nitro in my engines, in my ys- engines my 110, 140 and 160 dz i use only 30% heli fuel and i have never changed fuels ever even if it means i do not get any fuel for the day, i just make sure i never run out, i use magnum for my ys engines with unreal results and i use in my forst gas engione a da-50 i broke it in with stihl, five gallons then i went to klotzs at 17 dollars a quart it has to be good and my da-50 runs great with a xoar 22x8 turning 7800 rpm's and i have put some fuel through it without a problem. good luck and happy flying

I have a weed eater and it runs fine too
this has nothing to do with the ZDZ question but it looks like that is no criteria here
For those who are not familiar with the ZDZ, setup properly- power is excellent second to none - Been around too many engines to believe otherwise.
By the way , a loose prop will make noise and kill power -and typically break all bolts - very shortly-

All the prop bolts are tight.......I;m gonna reassemble it and try it again tomorrow with some fresh fuel.......

Make sure you fix up the ignition where it rubber through, that will cause you problems in the future if it has not already. Sometime by it rubbing through like you described, it can cause the spark to jump at that point (not to the cowl but from the inner core to the braid).

Have you done anything different to the engine from when it ran good to when it started to overheat and make the rattle sound?

Is there carbon buildup on the ring groove? The buildup can hinder head transfe to the cylinder and causes overheat.

I put a jmb pitts muffler on,,,it was real restricctive..I had to richen both needles almost 2 full turns out, the muffler still took a lot of power away. So I opened up the can and cut the outlet tubes down. The went all the way to the top of the can, now they are even with the bottom of the can, but it didn't seem to make a difference in power, just a tiny bit louder...

So was this the exhaust system you were using when it was running good, then did the modification to it? Or did you have a different exhaust system on whe it ran good then changed it out to this one then modified it from there?
If it is a rattling sound it could be pre-ignition. If it is more of a pinging sound it may be the resonation in the exhaust that some setup can make. Does the noise go away or get worse at a different RPM?

I had a side mont mufler on it with 2huge outlets on it for several years...After I put the pitts on it, I had a big powerloss and had to richen the needles a lot. I removed the outlets to hopefully let the engine breath a little better but it apparantly didn't help.

I just put it all back together and ran it... I set the timing back just a hair and didn't hear the noise any more...I don't have the cowl on the plane and the engine was still pretty hot after running about 1/4 tank thru it. But I checked my needles and they are almost 5 turns out each... The engine rpm or sound will not change no matter how far I back the high one out, the lowend makes some difference at idle...It's the older bing carb, maybe it's time for a new one, I cant find a kit for the bing.

See if you can get your hands on the WT71, very friendly on the 80rv

Chad

Try taking your carb apart and cleaning it out. Maybe there is a restriction in there. I have heard the WT71 carbs are easier to tune.

When you put it all back together and ran it, was that with the side mount exhaust?

I took the carb part and cleaned it a few months ago...... ran it with the pitts mufler.The side mount wont' fit on my sukhoi....

Try taking the carb apart and cleaning again, maybe something got in there and is plugging an orfice causing it to run lean. If you have the needles opened that much you should flood the engine or at least have the burbling sound. Also check the fuel lines from the carb back to the tank, including inside the tank. What Pitts do you have? What outlets did you remove or how did you remove them?

I'll try taking it apart.......I have the jmb pitts that rcshowcase sells... I cut the end of round the can off...The outlets were all the way at the top of the can on the inside with a couple of tiny holes in them I guess for sound purposes.I I icut the pipes off flush with the inside of the can so it would obe more open.

Sooooo does anyone have a carb they want to sell me?

Give Ralph a call....if he has a WT71, have him check it over and send it to you. If nothing else, send him your carb and/or entire engine...he'll make it right. He's one of the best in the business, great to talk to, he stands behind his work, and is seriously inexpensive compared to alternatives. It will be worth your time, make the call...

Ralph Cunningham
928 635 2455

Try cleaning the carb. If that does not help and you can, send the engine and carb in have it checked out.

agree. If the engine is still running very hot and the high RPM # is bad, then very likely there are some issues with the internal of the engine or ign. module. Send it in.