Well, no good. The engine ran strong and idled well, but a couple of manuevers into the Masters sequence it died. When it quits it is usually after some idling on a downline, the prop is still turning, it just won't throttle up and dies. On the ground the motor just does not sound right in the midrange. The RPMs will sometimes vary with no change in throttle position. I started with the pump regulator flush, but the motor hesitated going from idle to full throttle, and it would vary in RPM in the midrange, suggesting it was lean. I tried turning in the screw in 1/8 turn increments until it was too rich in the midrange, all to no avail.

When I first flew this plane last season, I was flying a 140DZ I bought from Tim Jesky, Andrew's alpha motor before he went electric. It was fresh from YS service. It behaved exactly the same way. I tried a lot of different remedies including a header tank, running it lean, playing with the regulator, all to no avail. The crank failed and that is when I purchased a new 160DZ, which ran like a clock once I got good pump for it. (When new it would blow the fuel line off the throttle body, the regulator was stuck closed. The bore of the regulator body was not machined properly).

The 160 ran great in this same airplane until the rotory valve failed a couple of weeks ago. I doubt the problem is related to the tank or cooling.

These motor are relatively simple. No adjustment except main needle and the pump regulator. My guess is something is wrong with the pump, but I have not figured out what yet. I am suspicious of the bubbles I see in the line going to the injector at part throttle. I also don't trust bench running. The motor will run all day long on the bench, as would my 160DZ with the bad regulator housing.


To summarize what was changed:

Pump Plunger
Pump regulator diaphram
Upper intake pushrod
Throttle Barrel O-Ring
Cleaned up Valve cover gasket surface
Leak Free gasket on valve cover
New intake valve adjuster (original was stripped)
New OS-F plug

The parts in the pump NOT changed:

Push me-Pull me valves and springs
Pump Body
Regulator Spring
Regulator O-Ring



From the basement of YS Hell . . . . . . . . . electric is starting to look better . . . . . .