RCU Forums - YS 63 and 91 problems

Hi Dave,

First off I only use 20/20 fuel and OS "F" plugs. I also am against leaning an engine to the absolute limit as I know how bad this can be.

The YS 91 is an engine I picked up at a swap meet and I have installed a new cylinder assy and ring as well as all seals to do the replacement of those items.

This 91 will run great in all aspects until I pick up my plane and shake it. Then it just flat dies as if the fire was put out.

I did this "shake test" to see if the fuel supply was being interrupted as the engine was dying on me in flight with no warning from almost any power setting.

My thinking is that a fuel supply issue should NOT show itself as soon as I shake the plane. I see no air bubbles in the fuel supply line.

So I'm guessing that possibly a bad glow plug is the culprit. This

Unfortunately I cant test my theory until I put the engine in another plane, as it flamed out on me and

I didnt perform well as a pilot with a deadstick Ryan STA.

What do you think?

As for the YS63,

It is in a friends Funtana and it is puking fuel out the carburetor after the system is pressurized.

It is also not responding to main needle adjustments as it should and even with a new OS F plug

it dies at ALL RPM's once you remove the glow driver.

Do you have a starting point for me on this one?

Thanks and Merry Christmas