YS 1.20 throwing props
 

My YS 1.20F will not throttle up without back firing and throwing the prop. It seems lean but I don't know how to adjust the low end needle. Where is it?
The engine will throttle up slowly after start up but won't throttle up warm.
I'm using an APC 17x6 prop and 30% heli, all synthetic fuel.

RE: YS 1.20 throwing props
 

These engines have a fixed idle, there is no adjustment. Since it is an older engine, you have either had it a long time or bought it used. There could be mechanical problems or possibly the fuel system is in need of repair.
The starting setting for the main needle is 2 turns open, the regulator screw should be set flush with the housing. Make sure that the tank is pressurizing correctly.

Throwing props is a sign that the engine is detonating. Is the prop driver face worn smooth? If so, it MUST be replaced before going further as it will NEVER hold a prop correctly.

RE: YS 1.20 throwing props
 

OK then. I'll send it in. What's the address?

RE: YS 1.20 throwing props
 

YS Service
1295 Industrial Court
Gardnerville, NV 89410

Phone 775-782-4562