YS 91 crappy idle help

[cdrking]

I have a YS 91 with about 35 flights on it since a new rear bearing and ring. It flys great in Idle up 2 at 1750 rpm with CP 30%, Hatori SB-16, 8.45 ratio in a Fury Extreme. Dual plug Viper head also.

I can't get it to idle worth a crap. I have tried rich and leaner on the idle/low needle. High is a few clicks less than one turn open and the mid is 1 1/4 turns out.

When I try to go from idle to hover it acts like it's totally rich. So I lean it to get the transition correct and then it cackles slightly and also hangs on the idle in throttle hold.

The fuel lines are all new and the filter is clean, I tried a new check valve. The only thing I haven't done is maybe pressurize the tank and use some soapy water to check the tanks for leaks. This is a new fuel tank. I

I wouldn't think it's an air leak because it runs great at 1750 rpm.

Out of ideas.

Jeff

[Ivan]

Don't know about the 91, but the 60's had a tapped hole that needed to stay plugged. The screw would fall out at times. I think Rick's had a write up on it.

You might look for any unplugged holes.

[bighands3d]

what plugs are you running it the viper head.

[DavidH]

When I try to go from idle to hover it acts like it's totally rich. So I lean it to get the transition correct and then it cackles slightly and also hangs on the idle in throttle hold.


Jeff,
The low end adjustment also affects the mid range and the high end. So when you lean the low end, the high and mid are going to need richen 2-3 clicks each.
Adjust the low end till the transisiton is clean. Then adjust the mid and high needles so they are not lean.

David

[cdrking]

I'm running an OS #8 in the top and a Enya #3 in the bottom.

David,

I'll try that and see what happens.

Thanks,

Jeff

[DavidH]

Jeff,
I just read your post again and realized your using the Viperhead. Before you adjust the needles any. Try this.When you crank the engine, also touch the glow igniter to the other plug and light it while the engine is idling.
I can tell you from experience, the other plug does not light till the engine is turning a high RPM. When using the Viperhead in contest flying I would light both plugs when I was starting the engine. I would put power to one plug to start the engine and then light the other one when the engine started. If I did not do this the motor would not run correctly till I got above hover rpm and the other plug would light.
Even Curtis when he used the Viperhead, he did the same technique. He would light both plugs when he started the engine. He does this at an F3C event. If your going to start the engine and not hover, say going directly to idle up. It is not a problem. But if your going to start the engine and only one plug and hover. The engine will not run correctly.

When only one plug is working correctly in the Viperhead. The motor will run, but it will run like the mixture has been richened a good bit.

David

[cdrking]

Interesting regarding the Viper and both plugs. I will try that, I thought about doing that the next time I flew. But I had the same setup before the engine rebuild and it idled fine.

Thanks,

Jeff