YS91FZ inverted problem?
 

I have this engine in a Tai-ji 60, obviously running it inverted. I can't get it to run right in the plane. Yes, I have checked the tank pressure, leaks and all the common things that happen to YS engines. Here's the weird part. When I pull the engine out and run it on the bench right side up it runs perfectly. I have 2 YS91FZ they both exhibit the same behavior. Is there some secret to running YS inverted that I don't know about. I really tired of fiddling with it. I just want to fly. The same engine was in a GP Giles 202 running on it's side. Pulled like crazy. Go figure.

TIA, Brian.........

RE: YS91FZ inverted problem?
 

Did you try leaning out your low end needle valve by turning it counter clockwise? You didn't mention anything about tuning your low end in your post.

RE: YS91FZ inverted problem?
 

Yes. I know the idle mix is an air bleed and works opposite direction from other needles. I am very familiar with YS engines. I have been using them for years. They have always been a pain to tune. When the temperature changes you are tuning.

The darn things runs great when it's on it's side or on the bench. I have always had problems running them inverted. I am really tired of it. This is my last attempt to get it to work. If I can't I am going YS free.

RE: YS91FZ inverted problem?
 

Try running the engine in the model, but place the model in a stand upside down so that the engine is running upright. If the engine still has problems, it's your installation and not simply the fact that the engine is normally inverted.

John

RE: YS91FZ inverted problem?
 

Now that's something I haven't tried. Not sure how I'll go it though.

Thanks.....

RE: YS91FZ inverted problem?
 

Do you have one of the Robart styrofoam cradles? If so, use it, and a friend, to run the engine with the model upside down.

John

RE: YS91FZ inverted problem?
 

I have a good friend who spent two full flying sessions trying unsuccesfully to get in his first flight with a YS 63 powered fun-fly mounted inverted. After the second session he took the plane home and remounted the engine horizontally. The next time out he got his first complete flight and went home happy.

RJ

RE: YS91FZ inverted problem?
 

Never had a problem with any YS installed inverted. All mine are inverted, 63,91, 120 etc.

RE: YS91FZ inverted problem?
 

Like PineBaron, all my YS engines are mounted inverted, and I never had a problem. It might be something simple as a plunger not completely sealing or a weak glow plug.

RE: YS91FZ inverted problem?
 

Ok. I ran it with the plane up side down. Guess what, runs just as good as it did on the bench. This is very frustrating. So much for my installation being wrong. Why are these engines so difficult to use? I've had 3 YS engines and they have all been a pain. They are great when they run right. Tons of power. But, at least for me, they are very difficult to tune. Especially when they are inverted. I am going to try a glow driver next.