Mr Lee,

I've always loved OS engines. They've always run well & been easy to tune properly. I recently built 2 planes for friends.A Kougar & a Sweet Stick. Engine, fuel tank, plumbing all was by the book & done 100% correctly.

I've never had any problem tuning the Mixture Control Valve or the Needle valve on any OS engine. I ALWAYS verify I have the correct OS manual settings for the Mixture Control Valve & Needle Valve.

For these two planes I bought OS FX46 engines on E bay. Low time engines in good shape.Installed new OS #8 plugs, 10% Cool Power. I had great difficulty tuning these engines. I finally got both of them running properly. But whereas it should take me 5-10 min to tune any OS engine, These took a LONG time & required a lot of patients. OS discontinued the rear needle valve. Was it because they're difficult to tune?

Further I double checked EVERYTHING on each plane. I eliminated every possibility of other causes. We simply can't trust these two engines to be reliable & not quit in the air. I have & do own many OS engines of many sizes & have NEVER had any troubles like this.

On 1 plane I replaced the 46 FX with an old but brand new never run OS schnerule 40. I had it running perfectly in about 10 min.
Thereby eliminating any possible cause other than the FX46.

Thank You Sir. You're a legend.