RE: 140DZ
 

Ok since it can't be any of the ideas I have for you.

Good Luck with it.


Troy Newman
Team YS

RE: 140DZ
 

You also mentioned earlier that it will vary rpm by it self at about mid range, if its not hunting (lean),
it could be front crankcase pressure affecting the regulator, which will affect the mixture.

I can give you a simple test to do, that will tell if it is a air leak problem or not.
You need to beg, borrow, or steal a vacume / fuel pressure gauge, they are used by motor mechanics to check fuel pump pressures
and vacume on car engines.

You have to make a simple fitting to go on the gauge so fuel tube will fit on, and also a t piece to suit.

On the DZ there is a piece of fuel tube that goes from the regulator to the front of the crankcase, it's about 1 1/2 inchs long,
remove one end and fit the t piece, use another short piece of tube and fit to where you took the tube off the engine and to the t piece.
Now use another piece of tube and run it from the gauge to the t piece, the gauge is now in place.

Start the engine and set a nice idle under 2000 rpm, MUST be under 2000 rpm, and see what the gauge reads,
it should be showing a vacume,any thing from about 1 to 5 inchs of vacume depending on the condition of the seals gaskets ring etc.
Now slowly increase the rpm and watch the gauge go from a vacume to a pressure, this is the supercharging starting to come in, go back to idle and it should go back to a vacume.

If it dosn't do as I just said, you have a air leak, and IT WILL NEVER RUN RIGHT, you could also change props to load the engine or block of some of the air flow from the cylinder to raise the engine temp to see if it will affect the vacume.

If there is a air leak then I would do a inspection of all gaskets, O rings, and even consider changing the front seal and crank ring.
And after doing what ever changes you do, check it again to see if you have a vacume.

If someone says to me their engine is not running right, the first thing I do is put the gauge on, saves me a lot of time tracking down the problem, you'd be surprizzed at how many times a air leak is at fault.

Team Crossman

RE: 140DZ
 

Well, it was not heat. I ran it tonight with the newly baffled cowl (Troy, I did add foam around the cynder head to keep the air close to it). I also pulled the stopper out of the tank and checked the piclup tube to insure it did not have a hole in it.

Still quit in the air.


This thing just does not run right, the midrange is rough.


XMANS, I might try what you suggest if I can find a gage. Otherwise I'm going to send it back to YS.

RE: 140DZ
 

I field stripped the engine this weekend. The piston ring and crank ring are OK. The main bearing looks good. One curious find was the cam, it had cuts in the top of the lobes (both intake and exhaust) that look like they were made when the spiral gear teeth were cut. I don't think this is directly related to the problems, but I'm going to replace them anyway. I have a new pump assembly to try to see it it cures the problems.

I installed my trusty FZ/L conversion in the plane to fly a contest this weekend and the engine ran great. Same pipe, same fuel system. It has good power, but not the nice linear feel of the DZ series.


The cooling mods to the Temptation really helped cool the bottom end of the motor. The spinner stayed cool after shutdown.

RE: 140DZ
 

I finally got around to working on this motor again. I installed a new cam, cam followers, and a new pump. The new cam is manufactured differently from the original, it appears to be machined steels rather than what I assume is some kind of powdered metal used for the old cam. It had a slight binding in the gears that cleared up after a short run-in.

The pump was the newer version, the top was a separate piece with an o-ring seal.

I bench ran it, it started well but was way too rich at 1-3/4 turns open. I leaned the pump about 3/4 turn in, then readjusted the main needle. It ran well at just over one turn open. It turned a Mejzlik 16X12 over 9200RPM, so for grins I tried a new APC 181.X10.1. It turned that prop at 8100 RPM on Powermaster 30%. The engine was hard mounted, so I would expect the number to be lower in the plane.

The engine ran very well at all throttle settings, something it did not do before, and there were no bubbles in the line from the throttle body to the injector.

I won't get a chance to flight test the engine until after the US NATS, I will post the results.

RE: 140DZ
 

Finally got it figured out. The regulators were set too rich. I had been adjusting them based on how the motor behaved at idle, but now I know that was wrong.

The light bulb went off when I noticed the needle liked to be about 1 turn out. I readjusted the pump so the main needle was at 1-1/2 turns out, now both motors are running well. Got through two US Masters rounds today and got to choose when to land. You could probably hear the choirs of angels sing . . . . . . .

RE: 140DZ
 

Hi,
Good you sorted it out ...

I found a good way to adjust my 160 DZ ...
I bring the throttle up to approx 25% and let it stay there . If the pump is lean it will surge a great amount ... Too rich will be clearly rough ...
Once the pump is set , the HS-needle can be set ...

I had huge problem adjusting a brand new 160DZ , and it took some time before i found the fault ...After some testing of several parts i found that the throttel barrell was leaking fuel from the "metering-groove" and straight into the air intake manifold.
Then i did some machinery to the barrell and installed a second o-ring to seal off both sides of the metering-groove.
Finally it worked like a rolls ....

Kjell Olav

RE: 140DZ
 

... took some photo of my reworked Throttel barrell , if it could be of any interest ...

One picture shows the Original barrell with 1ea O-ring . The other picture shows the reworked barrell with 3ea O-rings.

Reworked barrell : The middle O-ring is to seal off the metering groove ,preventing pressurized fuel to enter the air intake manifold. The far right O-ring is to seal off between the air-intake port and the pressurized air-manifold.

The rotation friction is just slightly increased, and for my futaba mini servo (3101); the job is easy ...

Kjell Olav

RE: 140DZ
 

Thanks for the tip on adjusting the regulator. In hindstight it makes perfect sense.