Hey guys, My ZDZ 80 blue head is driving me nuts. Right now it is so rich in the midrange that you can see a little black smoke sometimes. If I lean either needle even a 1/8 turn, it dies in the transition from idle to full throttle. It has a walbro. Are there any adjustments inside the carb? Being a rear carb motor, would it be worth venting the carb backplate into the fuse?
Thanks for any ideas,
Brian

Jaybird,

Sounds like you have a bad carb. That small of an adjustment should not have that dramatic of an influence over it. If you are comfortable with working on carbs, take it apart and make sure there is nothing in the carb creating an obstruction.Often times the screen below the armature for the pop-off gets "gunk" in it and makes the engine a bugger to tune. Also remove the needles completely and make sure they are not malformed and the seats are clean.

If you are not comfortable with opening up the carb, call Mike at RCS (RC Showcase). The engine is still under waranty, and I'm sure he will replace the carb.

David Fox

My ZDZ-100 had similar symptoms. Sent it in, turned out to be ther rotary valve.

Thanks, I'll pull the carb apart tomorrow and check the screen and needles. If that doesn't do it, I'll call RCS. How is there turnaround time? Its prime flying weather right now!!

its probably something in the carb or just a bad carb but one suggestion I do have is when adjusting the needles make only 1/16 of a turn increments, walbro carbs are sensitive enough that a 1/16 will make a difference.

jaybird....go onto rcshowcase.com and call mike dooley, he is an engine guru!

R.C. showcase will take care of you. I had trouble starting my super 80 and it only took one phone call to solve my problem and they even called back to check and make sure things were right. They have made a loyal customer out of me.

The biggest factor in turn around time is shipping. Mike turns things around in just a couple of days (typicaly), but shipping can add several days to this. If you want it quick, pick the quickest shipping method, and ask Mike to do the same. It may cost you a little more but sometimes it's worth it.

David Fox

Jaybird - the throttle plate rotating the wrong direction will also do this
IF you cut off the existing throttle arm (from the shaft ) to add your own arm- there is a good chance this happened.
I know some have advocated doing this -but in my book - not a good idea.
the correct direction of rotation for the throttleplate is suchthat the plate stops at first discharge hole in the bore -then - moves back -over the second-high speed hole(s).
also throttle plate must be at exact full open position when servo is at full throw open.
You would not believe the guys that have done this "arm change" and caused misery for themselves.
Ah hev fixed a few.

Mr Hanson, Standing behind the plane looking down, which direction would the throttle shaft rotate to open? I think mine is set up to open clockwise but I will go check for sure this morning. Who knows, I could have it backwards. Its worth checking.
Thanks!
Brian

did you cut off the throttle arm?
If not - you can't get it wrong the stock arm stops it from going backwards

Yes, I cut it off. Originally the engine was mounted on a POS Chief mount and the stock arm wouldn't work.

OK- then you easily could have it goingthe wrong way -
best is to pop it off look and see and figure best setup to run it the right way AND stop it on center -If it is a Tillotson or a Walbro - the ARM side of the shaft rotates counterclockwise to open- I just checked both, with arms on them

Just checked it, its going the right direction. (counterclockwise)
I guess i need to dig into the carb. What about the diaphragm cover being vented into the fuse? Does it make a difference in these rear carb motors?
Thanks,
Brian

Never in all years -seen a carb vent problem on the ZDZ.
something I can't see over the internet - is amiss -maybe dirty screen - -maybe something that neither of us is thinking about
pull it and watch the rotatation - remember the butterfly first touches low discharge hole - then swings back over the high speed hole