I've been running mine for a few flights....... stock muffler/15-6 APC/25% Castor, no problem..................

10 needed work, and 12 didn't from what I gather at this point.

Between a friend and I we have 2 each of the OS 91 FX engines. All have ran perfectly from day one.

That is 4 of these without any problems whatsoever. These have been purchased as long ago as 4 years ago and the latest last month.

Neither me nor my friend has had any problems at all with any of these engines.

I sure havent seen any problems at all with these engines. In my book they are fantastic!!!!!!!!!!!!!!

Between the 2 of us we have had 5 OS 46 FX engines, 2 OS 50SX engines, 4 OS 91 FX engines, 1 OS 46 SF engine and 2 OS 160 FX engines and all have performed perfectly out of the box. In my book I won't purchase anything but OS!! Except for a few Moki's and YS engines they are fantastic also.

Just my 2 cents.

I bought one. Then I read all the negative publicity about them. I have seen about 6 or 7 guys at our field spend countless hours and many deadsticks trying to get them to run consistantly.

I sold mine for a $75 loss. Never even took it out of the plastic bag or bolted it up to a plane. Couldn't be happier.

I've also bought a few MDS 148 engines. They don't run well out of the box. You gotta buy a different carb and spend a few gallons breaking them in on the stand first. Wish I had never wasted the money in the first place. A $170 engine with no muffler and a $45 aftermarket carb isn't really a bargain after all.

Not really worth it if you gotta pull your hair out to make it run right. No matter what brand it is.

Just my $.02

OK Heres what the FX91 poll looks like so far,

1) comments have been received on a total of 28 engines
2) 15 ran right out of the box no trouble and people love them.
3) 6 reguired some sort of fix and/or alot of effort to get to run correct but when the did people love em.
4) 6 are hated by their owners and cant be made to work satisfactory.
5) 1 is 50/50 without an opinion.


As I see it slightly more than half (54%) of the engines work right out of the box, therefore half dont. 21% require some after mkt fix and/or alot of time to trouble shoot. 21% of the purchases resulted in unhappy owners.

IMO other than this model FX91, I have been very happy with all my other OS engines both 2&4 stroke. Some take alittle more time than others to run to my satifaction but I expect that as part of this hobby. Having said that I would never puchase a product with the above rating and take the chance. Would you purchase a radio with that type of history? How about a servo that only works Half the time?

Mine ran ok for ten flights.........now overheats and dead sticks all the time.

Still haven't fixed it.

Hi Guys.
Mine had all the probs, gave up and sold it in the end, might add this on of the very few motors in 25 years of ic flying that had me beet !
Cheers.

Almost 50% are problem engines. It almost sounds like OS pulled a fast one and had Magnum build the FX .91!

I can't remember EVER having an OS engine that didn't run well either.

I am glad I didn't buy one of these,almost did then did some research and started turning up posts on all kinds of problems of leaning out from airleaks. thank god for this and other forums. Imho 200 dollars is way too much for this engine.

I was wondering what other brands have a 90 that has the power to weight that the 91fx has when it is running well.

Mines great! After one dead stick, so far so good. Stump puller!
Ian

Mines great never been out of the box!

Ok Gents... I can help you tip the balance:
CALC (Club La Ceiba) two 91 FX (and an OS 120 Surpass II) never were able to run reliably for their three "sequential" owner.. you now the "you are doing it wrong, give it to me I'll fix it" types..gave up on 'em

Tegus (Club Tegucigalpa) at least 5 to 8 91FX's are being used for several uses at the club.. from very expensive paperweights to door holders.. (last comment I heard WE hATe'em just Hate'em...)

Well.. here in HOnduras there aren't many modellers, but the 50 or so active would rather be using rubber bands for power than an OS 91 fx.

For anyone using them as paperweights or doorstops I would love to take them off your hands.

I've never owned an OS, except for possibly my Wankel, but I have 95 others of many different brands and configurations. So I know that there is no such thing as an engine that can't be made to run. And to be able to hate an inanimate object like an engine is, ah, well, I just don't know Cap'n.

I own one - its running a Grapner 15-8 prop, OS #3 plug and using 15% fuel.

It broke in easy and runs like a watch - never had a deadstick (well if putting it two feet deep in the lake doesn't count).

Nothing but good experiences with this engine.

Trade ya.... and I'll even throw in a MDS .40

The above statement is an accurate one...if you can find the problem, and if you have the materials to fix it. With air leaks, you have to order the parts...another wasted day at the field not flying. With case leaks more parts ($$$ ones) that OS will have to fix, because it was the fault of the manufacturing process and they are expensive...meanwhile the airplane is still sitting not flying. These engines are supposed to run out of the box. Every OS I've ever owned has ran flawlessly, but conversely, the pumped 4 strokes, and the 91's do not run out of the box. When a person buys an OS, they are buying an engine based on their good reputation, and they expect it to run out of the box, and they do have a good reputation. It's just that this particular engine is a real nightmare. I've been flying for a long time, and I've helped alot of guys tune and fix troublesome engines, but this particular one has not lived up to the high standards generally associated with the OS name. I found out this weekend while at the field that there have been others that have had this engine also, and all of them said they ran like crap. I heard everything from diffferent fuels, props, glow plugs, o-rings, gaskets, needle valve assemblies, bearings, and like me they all started looking for the 'hidden leak' and could not find it. These guys (like me) do not give up easily, but they all gave up on this engine. Most people don't wanna spend more time working on an engine than flying. It's too easy to replace it with something that will run and not have to be messed with. It is rewarding to fix a problem, but sometimes you have to ask yourself is this thing worth messing with anymore? I ended up saying no.

Excellent! I'll send you my OS FX 91 paperweight. I'm sure you'll have better luck than I. Just don't send me a bill for the aftermarket parts you'll need to make it run well, k?

Oh wait... Please define "run".

Heres another tally.
1) Ran right out of box, 17
2) Finally fixed it, 7
3) Hate it, 15
4) 50/50, 2
Our friends in the Honduras had a very bad experience (see thread) and pushed the "Hate it" column up considerably. On a better note I have now gotton one of my two to run. Wont yet pull any stumps but not flaming out either. I posted in a seperate thread the steps that got mine to run. Nevertheless that stats paint a pretty straight forward picture so far.

Still not running right....OVERHEATING!!!!!! Gonna send in for service I think.

funny that most of the clones mag/sc/asp run fine out of the box?????????

Pssssst it's vaporized ahcohol not air bubbles. I love saying that.

Adrian those other engines all have bolt on remote needles instead of an integral casting. That's an added thermal junction to resist the heat.

Why wasn't this poll done using the poll provided by the board?

I can't say that I hate the engine as of yet but it has been a pain in the rear. I am just getting the bugs worked out and after a few more runs I will make a decision then.

I can say that I tend to dislike it thus far and will not purchase another.

Blackie

I firest took the baffle out of the muffler on my OS.91FX mounted on a Extra 300, it didn't work too well. Put it back and have switched from 15% to 10% nitro and it works fine. Pulls my 9 lb Extra around pretty good. Very seldom ever have a dead stick. I don't care for the three piece muffler, it's come apart on my a couple times. But overall its been a good engine, bought mine used on E'bay, it has been worth it.