OldRookie

My Feedback: (13)

I am just about to purchase an OS 91FX.
I am looking for input (good or bad) on this engine.
There is always a lot of talk on the poor needle valve assembly that leaks air. I am never sure if this problem is fixed on the newer engines or not.

Greg

Taildrager-inactive

My Feedback: (11)

Old Rookie: Welcome to RCUniverse. The fx line of OS engines have allways been a good choice as to value, user freindleness, and good power to weight. I think you will be pleased with this choice.

AirGar

My Feedback: (7)

OldRookie,

I had a F-16 (.60) with this motor in the nose, if you're looking for rpm's, get something else. It runs good, idles well, but I think you could call it a sport motor. I even put a Mac pipe on mine and that didn't help much! Sold the plane and kept the motor....don't know why though!

What are you going to put it in?

Gary

djlyon

You should like this engine. Mines great and very powerful. It pulls a Calypso around. I wouldn't worry about the bubbles. The simi-controlled test I ran suggests the bubbles are mostly vaporized ahlcohol, at least in my engine.

Mode1

My Feedback: (10)

I have one. I received it for my birthday a few months ago. I had not asked for it. At the local field there had been a few complaints about "air bubbles in the fuel line going from the needle valve to the carb, and problems "adjusting the needle valve". My engine was purchased from Tower so I called their service department (Hobby Services (217) 398-0007). I was told the factory o-rings on the needle valve were sometimes developing flat spots. This could cause air leakage. Hobby Services shipped me a new and improved (different rubber) set of o-rings at no charge. The part number on the plastic bag is: 24981837 and the number on the invoice is: OSMG 7388-24981837. I have only bench run my engine and so far. It starts easily, idles great, has no needle valve problems. I have mine in a Kange Cap 232 with a Pitts type muffler and I suspect it will be a fine engine for this aircraft.
Bob

OldRookie

My Feedback: (13)

I will be putting it in a Bruce Tharpe Delta Vortex.
I have heard that is a great combination.

Greg

Derek8819

My Feedback: (9)

I have a KAngke cap( nice flying plane and BEAUTIFUL!) I put a tiger shark .91 on it and it hovers at full throttle. yours should hover around 3/4. takeoffs are easy and tracks like nuthing you will ever see. great for pattern and does some nice 3d (BLENDER!!!!). Keep your landing speed up and you will see the landing grear block is weak. lands like a jet. You will enjoy it in the air though. send me some pics when your done.

w0mbat

My Feedback: (1)

I purchased one in December 1999 - from day one it had air bubbles in the line and would overheat in the air. It also had a strange sound when in the air - almost like a tin can sound no matter how rich I ran the engine. I have tried new orings, new muffler, 4 different airplanes, larger fuel line, smaller fuel tanks, glow plugs etc. I have finally isolated most of the bubbles but it still overheats and has that tin can sound. I am running a 14 x 6 or 13 x 8 apc. The only way it doesn't overheat is if I turn it so rich that it doesn't have any power. Then it will run about 10 min before dying. I fellow club member just purchased a new OS91FX a month ago - it ran fine on the test stand and on the groundbut did the exact same thing as mine when he got it in the air. He has been flying for about 30 years and has never experienced this type of problem.

I finally sent my engine to Hobby Services last week - we will see what they have to say. On the phone, they said that they never had any complaints on the engine!!

KingAirJockey

My Feedback: (-2)

I've had one with the same exact problems as described above,It has been in different airplanes,had different fuel lines installed(larger),its been sent back to hobby services and had orings replaced and so on and so on.The motor would start right up,and have great power,but after about 7-10 minutes would always quit even after all the fixes.I guess I just got a bad one.I sold it for 50 bucks and bought a tigershark 75 for 100 bucks.This thing rocks,incredible power,easy starts,instant transition.

FlyinRazorback

My Feedback: (8)

I pull my WM Midget Mustang around with a 91 FX and it hauls. The enigine does run a little hot so make sure you ventilate it well . I typically use a 13x8 or 13x9 APC prop and engine gets in 10,000 RPM range. I have been flying this plane / engine combo for the past year and it is the most reliable setup that I have.

OldRookie

My Feedback: (13)

I finally broke down and picked up an OS 91FX at my LHS. He gets $189.99 plus our state tax = $202.81.

Thanks Flying Razorback for the prop recommendations. The largest prop that I can run on the BTE Delta Vortex, would be a 14". The Delta Vortex is a little draggy with the 5" thick wing, at the center. I should probably start at a 14 X 6, if I want to run a 14" prop. I could even see a 3 blade prop on it.

Derek... I'll send you off a picture when I get it done, just don't hold your breath...It could be late spring at the earliest. I have a lot of good projects to finish up first. And I am not a fast builder.

Greg

FlyinRazorback

My Feedback: (8)

Speaking of the Delta Vortex, is this the one recently featured in MAN (or maybe it was RCM). Looks like a sharp plane and a blast to fly. I gave my wife the option of buying the Vortex, Cermark F16, and Yellow Cap for Christmas. She chose the F16 which I will put a Jett 90 on. Let me know how the Vortex flies, my b-day is in March so who knows?

BTW, I use a 14x6 APC occasionally on my OS. Does o.k., but for some reason the engine seems to run better with the 13" props. However, my landings are alot "cooler" with a 14" up front.


AirGar, which F-16 was it that you had? If it was Cermark's, how did it fly? What was it that made you sale the plane?

djlyon

I used a 13/10APC on mine and the engine liked it a lot but the plane wouldn't slow down. I switched to a 13/8 3 blade master and the plane likes it a lot better and the engine is real OK with it so I'm happy.

AirGar

My Feedback: (7)

FlyinRazorback,

I had the Cermark .60 F-16 "Thunderbird scheme".
It flew fine, but was not fast enuff for me,it was a combination of the motor sucked, and the "fake" turbine inlet that just created too much drag. That's why I now have the Cermark .60 F-20 with a Jett .90 out front!! ahhhh...much better!!

Gary

mss28

What about other engines. ANyone out there had success with other model maker engines? All we hear about is OS and I think people buy these things just because they are more expensive. You know people are always thinking that the more something costs the better it is. I don't think that way, however, I have never had the opportunity to fly anything else. I did have a FOX .40 and a Super Tiger 2000 one time and these engines ran great.

These engines aren't that complicated as long as you buy a good one with ball bearings.

What are everyones thoughts on this?

Thanks

MArty