Bobt2

My Feedback: (4)

so, it sat on the shelf awhile. put on a brand new walbro carb, bought new high test gas, mixed 40-1 with penziol. set the needles to 2 turns open and did the 5-5-1 starting .started right up and idles smoothly. however it will not run at high speed. no matter where I put the needles, including falling out open it will not run at high speed,.but it will idle all day with no quiting. if I put the choke 1/2 closed than it will run at full throttle.open the choke, it sounds like it goes lean and dies any ideas ?, I,m at the end of my rope.

Zeeb

My Feedback: (41)

It's possible to rotate the throttle butterfly in the opposite direction which will produce the symptom you describe.

speedracerntrixie

My Feedback: (29)

It sounds like the pop off pressure is too high. Under the diaphragm there is a spring loaded fork that controls fuel flow through the carb. If the fork is adjusted too low the pop off pressure is too high and the diaphragm does not have enough movement to pull the metering needle off its seat long enough to get enough fuel through. The fork can be bent outward and this will increase the fuel flow and the needles will become responsive again. Word of caution, this is a very delicate adjustment. .020 of adjustment is fairly large. Adjust too much and the metering needle will not seat and the carb will leak fuel. Before making an adjustment take a straight edge and place across the carb body just above the metering fork. The fork should be exactly parallel or slightly out from parallel to the straight edge.

Bobt2

My Feedback: (4)

the butterfly is right, I did find the timing off by about 2 deg. it s.b 6 and I measure about 4 I wonder if that's the issue? this is a brand new walbro wj71.

All Day Dan

My Feedback: (5)

Here’s an exploded view of the carburetor. Notice that the diaphragm, item 29, is against the cover with the four screws not the body of the carburetor. Dan.
http://wem.walbro.com/walbro/product...71-1&Series=WJ

All Day Dan

My Feedback: (5)

That’s an unusual timing. They usually run around 28BTDC. Dan.

Bobt2

My Feedback: (4)

on the carb, it's new.should be good for 100cc engines. can they be defective? have people had this kind of issue before? as to the timing, that is from the zdz/troy bilt web site.this is a rotary valve engine, not the usual reed valve. don't know if that makes a difference.

All Day Dan

My Feedback: (5)

If the engine had been run before it sat around for a while, the diaphragms may have deteriorated during that period of time. It’s not that difficult to change them and check the carburetor while you’re doing it. That timing still sounds strange. There are plenty of guys watching this forum with more experience than I have that can comment about it. If it is correct, make sure you are using an ignition module that is timed to run at that firing angle. Dan.

Zeeb

My Feedback: (41)

Not actually it isn't unusual, it's a measurement between two points in mm not degrees....

For the OP; I suppose it's possible that the timing is an issue but I'm not sure about that being the problem. I have found that my ZDZ's like 6.5mm on the timing and they are cold blooded. Once started they need to warm up some before they'll play.

Bobt2

My Feedback: (4)

dan, please read the post. this is a brand new walbro

All Day Dan

My Feedback: (5)

Got it. Just trying. Dan.

willig10

Are you sure the butterfly is opening 100%? Also are you sure the choke butterfly is 100% open when at full throttle?

Glenn

Bobt2

My Feedback: (4)

yes and yes. the cowl is off. the throttle shaft is marked and the choke is visible. I have quite a few gasers and never had this before. all the other engines are da's tho. I,m leaning towards a bad carb, even tho it's new.i didn't have this issue with the old tillison[but it was a pain to start]

kmeyers

I just read this and the first thing that came to mind was not a defective carb, but, a defective carb installation. Particularly I would first check that the crank case pulse pressure to the walbro's pump side is not blocked missing or otherwise wrong.

Bobt2

My Feedback: (4)

it has a new gasket and the holes line up. but, I was thinking maybe I should also use some permatex sealer?

Zeeb

My Feedback: (41)

Not sure I'd use any gasket sealer. You might try what we do with the full scale engine gaskets which is to rub some Lubriplate grease on them to soften them up and they usually seal just fine. On the pulse hole; I've never played with the Super 80 and you say "the holes line up". On my ZDZ's there is a hole in the back of the engine that is on the opposite side of the hole in the Walbro carb. There's a channel in the phenolic block that's between the carb and the engine and only one hole in the gasket which lines up with the carb and that channel must go toward the carb. The channel is only cut into one side of the block.

If all that is correct, I suppose an air leak might be causing the issue but it would have to be a dandy. You could fatten up the top end needle a bunch and see if it will accelerate as a test? The only other thing I can suggest is that you try contacting Dick Hanson via PM either here, FG, or RCGroups. He knows ZDZ engines really well and used to be part of ZDZ's development team and a beta tester for their engines.

Bobt2

My Feedback: (4)

zeeb, top end needle opened to where it was off the spring tension[more than 5 turns] and still the same. of course it quit when it came out, and again, the idle is perfect. I ordered another carb just for fun.

Bobt2

My Feedback: (4)

so, I wonder what crow taste like? reread all your posts again. got out the flashlight and got into the back of the engine in the fuse and had both carbs in my hand.after a while I found the issue. I mounted the carb upside down. the pulse holes were 180 deg apart. how it ever ran and started is a mystery to me.must be my 65+ years. I,m sure it will run fine now. thanks to all.

Zeeb

My Feedback: (41)

Well if the Super 80 is different than my 50NG, 80RV or 100NG then maybe the holes are supposed to be on the same side. In my engines the holes are indeed 180 degrees apart. That is what the channel cut into the block is for; to "conduct" the engine pulse to the carb. That block has one hole drilled in it that goes all the way through the block. It fits on the engine with the pulse port lined up with the hole in the engine. Where it comes through the block, the cutout or "channel" starts. It follows the curve of the opening in the block which is the same diameter as the engine intake and just ends. This is where the hole in the gasket for the carb and the hole in the carb baseplate are lined up.

Wish I had a picture or two but I don't so I hope that helps.

Bobt2

My Feedback: (4)

zeeb, no slot, just a single hole. I was in there with a flashlight

Zeeb

My Feedback: (41)

Again, I've never had the Super 80 so it might be different than mine but I suspect not. That being the case you have to be able to see both sides of the block as it's only cut on one side. If that block is installed backward it won't play. If you cannot see the slot/channel with the carb off I suspect the block is on backwards since that channel/slot has to be toward the carb.

Zeeb

My Feedback: (41)

Well I just tried to find a parts/maintenance manual for your engine and ZDZ has dropped the old website which had diagrams and parts lists for all the engines. That website and even the domain name for the English version is up for sale.

I guess you could try calling TBM if this last possibility doesn't turn out to be the issue but I've not been impressed with TBM every since Gene quit running the business and hired a manager. Were it me, I'd be calling AMR who is the Canadian importer/distributor for ZDZ.

Bobt2

My Feedback: (4)

maybe I,ll pull the engine and check.however, as this is one of the few arfs I bought there are pics in the manual of the zdz super 80 installed and it clearly shows the carb installed. I had it in with the needles on the wrong side which backed up what I found. the plane is the aeroworks 85cc yak and the manual is on their site

Bobt2

My Feedback: (4)

zeeb, ok. heres the deal on the block.yes it's on right because the mounting screws into the crankcase are recesed on only one side.they have to be flush with the carb side. bob I took off the block anyway. there is a short, maybe 3/8" long slot to line up the port in the crankcase with the hole.but that has to be on the inside to line up.so, yes, I had the carb on upside down!

Zeeb

My Feedback: (41)

Glad you got it figured out.