Hi Guys,
I bought a YS91AC about 8 years ago to put in a 4 star 60 I was going to build. I was new to the hobby and learning to fly a PT 40. The four star was going to be my second airplane after I learned on the trainer. To make a long story short 8 years later I am about to finish my four star. My question is this, my 91AC is still brand new sitting in the box it came in 8 years ago. Do you think it is still good to go? Can any parts go bad sitting for so long?

Thanks---

P. S. Still have my PT 40 to Learn on. Cleaned all the dust off and it started right up!

[8D]

Its probably in good shape.

I would recommend putting some oil in it before you try to run it. It doesn't take too much. It will make it very hard to start...But a couple drops in the carb, a couple drops in the glow plug hole, and remove the cam gear cover and put a few drops in there.

The oil that should be used must be all synthetic. NO Petroleum products. The engine has many silicone parts and the petroleum based oils will attack the silicone parts. Mobile 1 synthetic 0W-20 motor oil works. But can be a little too thick. So you have to use very little.

The oil the engine was stored in originally is likely still there but it has probably thickened up. So you may have some trouble getting it going at first. Patience and realize that things are a little gummed up and it will work.

I would just put a bit of oil in it and then turn it over. Hook it up and try to start it. If all goes well it should fire right up. If it doesn't you may need to take the regulator apart and clean it with raw fuel.

I recommend some 30% heli Cool Power and about a 13-10 or 14-9 maybe a 14-10 prop. You want to run the 91 at about 9200-9500 at full power. So depending on your choice of fuel you may need to run a smaller or larger prop. I would not personally recommend anything less than 20% nitro and you need 20% oil content. DO Not use any kind of 4 stroke fuels. they don't have enough oil for the YS engines.

Good luck with it.

Troy Newman
Team YS

Thanks Troy!