MY OS 91FX will not transfer from idle to full speed with out bogging down or stalling any ideas
and could fuel thats old be a problem? The fuel is a yr old.

if the jug was sealed and stored properly the fuel should still work. easy to check with some fresh fuel. might need to reset the low needle

Hi!
Have you set the idle needle?

Regards!
Jan K
Sweden

Sounds like your low speed idle screw may be too far out?

Enjoy,

Jim

yeah maybe need to adjust idle needle high speed adjustment won't make a difference. Do you think I'm to lean on the idle setting?

Bogging usually indicates a too rich idle mixture condition, turn the idle screw in 1/8 turn at a time.

Ok I will try that thank you Taildrager! Here are a few pics of the plane.

Here is a trick for you but you need to remove the cowl, once you have the low end right, its rare that you need to readjust it in any given season unless something else goes wrong.

While the engine is running at an idle, remove the fuel line from the carb or pinch it until the engine quits but listen to the rpms. If the engine rpm increases as the engine quits, your low end is too rich. If the rpms just go down, too lean. I set mine for a very slight increase. The dialin your high end as necessary

LOL Doh update on my engine running problem! Seems that when I hade the engine off the mount and reinstalled it I forgot to reattach the fuel tank pressure line to the in cowl muffler! Amazing how well it runs now!

So like a fool, I went out and bought an OS .91 FX two stroke. I read some of the threads here on RCU about the metal remote needle with its fuel bubbling issue and its air leaks, so I THOUGHT if I found one with the composite remote needle, I would be ok... Stupid me for thinking that... Well as you can tell, I got a real stinker anyway. After 1 1/2 gallons of fuel, 4 weeks of available flying time, and A LOT LESS HAIR ON MY HEAD, I'm calling it quits with this OS Engine (OS must stand for Outright S**TTY) If I set the high end needle to max rpm and then go 3 to 4 clicks richer, (200 to 300 rmp loss) and then set the low end for best transition and idle quality, the midrange is soooo rich that if you throttle back and after a few seconds throttle up, This engines ALWAYS burbles, stumbles and dies. Yet another deadstick. In 4 weeks, I have yet to fly more than 5 laps on any given flight, and never without a deadstick. I have read the posts here about cures for the rich midrange, followed the advice of all of them, and even had several of our clubs best engine guys (Some of which are OS ONLY guys) and not one of them can make this POS run right. I will either return this thing to OS for an exchange on a different engine, or I will just dump it on ebay. (Yes I'll tell everyone in the listing all of this. (I believe in being honest)

Wouldn't give up my OS 91FX in my corsair fer nuttin! Ran like a champ before I screwed up the piston ring by not getting enough after run oil in the cyl. then the ring froze to the piston. Took the engine apart cleaned it,put a new ring on reassembled forgot to hook up exhaust pressure line which caused it to die on idle return from full hook up pressure line final adjustments and its running like a fine swiss watch!! Frankly I think the 61fx and the 91fx are some serious work horses!!

1) Has the engine been sent to the service center?
2) What is your fuel like? Fuel system?
3) A too-rich throttle-up usually means that the idle mixture it too rich. The proper way to set up the engine is to start out with a much too-rich idle mixture, get the full-throttle mixture adjusted so that the engine's running just rich of peak RPM at full throttle. Then throttle down to get the idle mixture adjusted. If it goes too rich on throttle-up, the idle mixture's too rich. You'll need to lean it a bit.

One thing to also consider is the idle RPM. Getting the lowest-possible idle RPM comes at the price of transition. You may have to give up some idle RPM to get a good transition. Any idle that's 2,300-2,500 RPM is OK. Lower is "gravy".

Hello Bax,
I thought that you might pop in on this one. Thanks. I HAVE followed just what you said. Actually so have three other fliers in our club. Been there done that... Even bought the T-Shirt. This thing just refuses to run and transition from 1/2 throttle to full throttle. Fuel is new... WildCat 2-4 stroke 15% with 18% castor synth blend. That’s another thing that has been tried. We tried Cool Power 10%... Sig 5% and even one tank of WildCat YS 20/20... Although the YS fuel was slightly better on the high end, it wouldn't transition either. We have even tried removing the baffle to lower pressure to the tank, and running NO PRESSURE LINE to the tank. We can compensate for no pressure with the needles, but it still will not transition. It acts as if it is loading up too rich, it burbles coughs spits sputters and dies. We have run it at length on the stand and in the plane, changed ALL of the hoses, clunks, changed tanks, and even changed brands of tanks. No help.

I do want to say that I have not sent the engine in for service. And I am not likely to do that either. You see, with all of the horror stories of the guys at the field in this club and two other clubs of which I am a member, I have very little faith that I will even get the same engine back. I know that I am not speaking from personal experience, but I have heard all the problems from people I know and trust... but Company reps would tell me that the service department is completely trustworthy and hardly ever makes mistakes or gets something wrong... Who would you trust?

Please understand that it is not my intention to sit here and badmouth a particular company, person or service department. I am just convinced that I have a real piece of cast aluminum junk suitable for hanging on the nearest wall and that is about it. It certainly is not worth any more of my time or money to try to get it repaired, I wouldn’t even consider spending another dime on a dog to find out it still has more flees

[b]BoltLocker:

I have to come to the defense of Bill Baxter and Tower Hobbies.

To get a repair accepted as warranty and not owner's respossibility sometimes takes a whale of an argument, with a strange run problem you might not see any difference when it comes back, but the work they do is excellent quality.

And they are not a business that will switch engines without telling you first and having your agreement.

Might seem strange to hear me defending anything to do with OS, but regardless of my opinion of the engines, Tower is an honest business, and Bill Baxter is one of the good guys.

Bill.

Hi Bill,
First of all, my apologies for taking over this thread. As I said, in my earlier post, I do not wish to bad mouth Tower Hobbies or Bil Baxter. I simply do not have any faith that if I do send the engine in, that it will be fixed and returned. I myself am a small business owner. I know that customer service is a huge issue. I do not have any experience directly with Mr. Baxter. But I will say that Tower Hobbies is usually my first stop for material and supplies. I have had great service from the retail side of Tower Hobbies. but I am a dedicated reader of RCU. My statement about not trusting the service department was not intended to be a statement about Tower or Bil Baxter directly, but a statement of Engine Service in General. Sorry, No offense intended.

So anyone wanna buy a nearly new OS 91 FX?

I don't mind you took over my thread I was finished anyways I got my 91FX runnin GRRRRREAT!!
Very good possibility it wasn't broken in correctly and you have a sleeve out of shape and are losing compression. But IMHO I still think its an adjustment issue.

[b]Bolt Locker:

The one that is notorious for switching engines is Hobby People/Global Hobbies, the importer and service point for Magnum engines.

But even here it's not bad, in fact it's a good thing. When they switch engines they send a brand new one to replace your old damaged one.

How's that for super warranty service?

Bill.