RE: Lets take a poll on the FX 91  
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    • All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> RE: Lets take a poll on the FX 91
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    RE: Lets take a poll on the FX 91 - 9/26/2003 7:12:36 PM   
    bentgear


     

    Posts: 2750
    Joined: 3/25/2002
    From: Brandon, MS, USA
    Status: offline     		john, hands down, the OS 40 LA is a much better running engine out of the box than the 91FX. The only long term fix on the 91 FX is a remote needle valve, perry pump or cline regulator. I have only seen one 40 LA that could not be made to run good just with a careful breakin and adjusting of the needles. I have never seen a 91 FX that did not need work.
    Ed M.

    (in reply to Kirk RC)
           Post #: 126

    RE: Lets take a poll on the FX 91 - 11/7/2003 3:10:26 PM   
    TD1


     

    Posts: 256
    Joined: 9/10/2002
    From: Banda, , ANGOLA
    Status: offline     		I am also struggling with my 91 fx. I want to know if we can use the carb from the 91 sx-h the heli version of the 91 fx? or use the 91 sx-h for airplanes? That should take care of most of the problems related to the remote needle valve.

    TD

    (in reply to Kirk RC)
           Post #: 127

    RE: Lets take a poll on the FX 91 - 11/9/2003 6:44:49 AM   
    PatternPilot



    Posts: 546
    Joined: 11/17/2002
    From: Knoxville, TN, USA
    Status: offline     		Love my OS91 FX.. using in Viper 91 swinging a 15X10 apc prop without any pump and only using pipe pressure with tank on cg.. and no bearing problems... Some people have said a very easy fix for a poor running engine is add 2 head shims to it and it will run great.. Mine runs runs at 8900 rpm with the 15x10 and NO extra head shims..Oh bTw the verticle is out of sight !!

    scott

    (in reply to TD1)
           Post #: 128

    RE: Lets take a poll on the FX 91 - 11/9/2003 3:04:29 PM   
    nedyob


     

    Posts: 1240
    Joined: 2/5/2002
    From: NORTHWOOD, IA, USA
    Status: offline     		Hello all OS 91FX owners,
    I recently got a Edge 540 and had my OS 91 FX w/pitts muffler in it. Reading all the problems with the 91 FX I oppted for a ASP 91 and the plane flies great. If OS fixes the problem with the 91FX I will be more than happy to swap engines.
    Like a lot of you OS owners have said OS need to address the problem and come up with a fix.
    NEDYOB

    (in reply to PatternPilot)
           Post #: 129

    RE: Lets take a poll on the FX 91 - 11/21/2003 7:08:42 PM   
    Robotech



    Posts: 1072
    Joined: 1/17/2002
    From: Pine Bluff, AR,
    Status: offline     		Bought two of these at the same time. 1 POS, 1 great. Sent the POS in for warranty repairs. They replaced the bearings and piston. Now it runs like a top. After about 60 flights the good one has developed the same problem the POS had becoming the new POS.

    I would have to say that if you spend the extra money for what is supposed to be the premium brand you shouldn't have to jump through hoops to get a decent running engine. If I wanted those kinds of prooblems I could save money and buy a MDS.

    (in reply to nedyob)
           Post #: 130

    RE: Lets take a poll on the FX 91 - 11/21/2003 9:25:58 PM   
    STG



    Posts: 3500
    Joined: 7/3/2003
    From: New Richmond, WI, USA
    Status: offline     		Between the my friends and me we have 11 of them that have never done anything but pull like a monster. Never a dead stick in about 700 flights between us the last 3 years. Ran on pitts mufflers, stock mufflers and tuned mufflers. I do not doubt that others have had problems. I would be mad as ******** if I had to deal with a bad one. I would want O.S. to make it right by me. I love them. 15 x 6 is the prop to run for sport flying!

    _____________________________

    Good Flying to you!
    See Blog for RCU Video's

    (in reply to Kirk RC)
           Post #: 131

    RE: Lets take a poll on the FX 91 - 12/9/2003 2:23:29 PM   
    selnekav


     

    Posts: 262
    Joined: 12/9/2003
    From: Karmiel, , ISRAEL
    Status: offline     		Hi
    Can you tell me how to make it work ( OS FX 91 )
    i will appriciate
    Thanks,
    Shlomo.

    (in reply to Spicoli)
           Post #: 132

    RE: Lets take a poll on the FX 91 - 12/9/2003 11:35:15 PM   
    PilotLight



    Posts: 855
    Joined: 8/15/2003
    From: Benton Harbor, MI, USA
    Status: offline     		I've finally got the engine running good, but it was on a engine test stand. I received a new rear cover plate. The old needle valve was broke off the engine so I let it hang by some blue medium fuel line. The engine ran OK, but the important thing was there was NO air in the fuel line. Next we changed the glow plug from a Fox with an idle bar to a 0 S #8. (more improvement) Finally, we noticed the fuel tank had a lot of fuel splashing inside so we decided to balance the prop. We found the prop was perfectly balanced on a magnetically suspended balancer, so we installed the propeller so that when the piston was at top dead center the propeller was horizontal not vertical. This produced a lot less vibration and the engine ran perfectly.

    To sumarize:

    * New fuel tubing between needle valve and carb
    * remove needle vavle from rear of engine (eliminate vibration)
    * run OS plugs
    * mount prop horizontally to piston top dead center (this made big difference)

    (in reply to selnekav)
           Post #: 133

    RE: Lets take a poll on the FX 91 - 12/10/2003 7:11:38 PM   
    2thelmt



    Posts: 102
    Joined: 12/28/2001
    From: Acton, ON, CANADA
    Status: offline     		What position is your prop when the piston is just "bumping" the begining of the compression stroke? - I'm just wondering where it would be if there was a dead-stick landing.

    < Message edited by 2thelmt -- 12/10/2003 7:14:59 PM >

    _____________________________

    "The only way of discovering the limits of the possible is to venture a little way past them … into the impossible.&q

    (in reply to PilotLight)
           Post #: 134

    RE: Lets take a poll on the FX 91 - 12/10/2003 9:02:25 PM   
    PilotLight



    Posts: 855
    Joined: 8/15/2003
    From: Benton Harbor, MI, USA
    Status: offline     		The Prop is straight up and down when the engine is "bumping the compression stroke". I was concerned at first about problems with the prop striking the ground, but it's not even close as long as I don't stuff it onto the runway on its nose. I also use an APC prop. Just make greaser landings.

    < Message edited by PilotLight -- 12/29/2003 6:49:58 PM >

    (in reply to 2thelmt)
           Post #: 135

    RE: Lets take a poll on the FX 91 - 12/18/2003 8:46:21 AM   
    KevinVogt



    Posts: 42
    Joined: 9/27/2003
    From: Henderson, NV, USA
    Status: offline     		I own an OS91FX and crashed the same plane three times due to dead stick situations. I sent the engine back to them and they said that my new motor had a scored ring and cylinder liner. They replaced both. I haven't bothered to even start it since it's return. It sits in a cabinet while I run Saitos from now on. I tried everything with this new OS91FX to make it run well with no luck.

    I hate it.

    Cheers,
    Kevin

    (in reply to Kirk RC)
           Post #: 136

    RE: Lets take a poll on the FX 91 - 1/2/2004 12:30:47 PM   
    propwinder


     

    Posts: 5
    Joined: 5/6/2003
    From: Stone Mountain, GA, USA
    Status: offline     		Major POS --------- HATE IT I own one. Will not tune right, either runs to rich or leans out in flight, also glow plug loosens up all the time.

    (in reply to Kirk RC)
           Post #: 137

    RE: Lets take a poll on the FX 91 - 1/2/2004 2:42:53 PM   
    2thelmt



    Posts: 102
    Joined: 12/28/2001
    From: Acton, ON, CANADA
    Status: offline
    quote:

    ORIGINAL: propwinder

    Major POS --------- HATE IT I own one. Will not tune right, either runs to rich or leans out in flight, also glow plug loosens up all the time.


    Do the mods as listed and you will love the power!
    Mine has not dead-sticked since modding.

    _____________________________

    "The only way of discovering the limits of the possible is to venture a little way past them … into the impossible.&q

    (in reply to propwinder)
           Post #: 138

    RE: Lets take a poll on the FX 91 - 1/2/2004 3:52:24 PM   
    Flyboy Shady



    Posts: 83
    Joined: 12/22/2003
    From: Stockholm, SWEDEN
    Status: offline     		A typical OS problem (all 2-strokes?) is that the suggested needle valve settings and idling mixture settings in the manual, are completely up creek.

    I do not understand why OS recommends 2,5 turns open needle valve when in fact the engine runs its best at just over one. The same goes for the idle mixture. The factory preset is up the walls.

    But once you get the settings right, as with most two strokes, they run flawless.

    (in reply to Kirk RC)
           Post #: 139

    RE: Lets take a poll on the FX 91 - 2/1/2004 7:08:04 PM   
    4sylvester


     

    Posts: 19
    Joined: 9/22/2003
    From: Orlando, FL, USA
    Status: offline     		Add another dissapointed owner to the list. I took a chance and bought the FX91. 2 months of problems. However, I haven't had issues with leaning or air bubbles. My engine runs great at the top end and idle. But the engine runs erratic in the mid-range to low range. Most definitely seems like a fuel delivery problem but isn't fuel delivery controlled by the low speed needle at 10 to 50% throttle? In addition, I get loud knocking in the mid-range. Going from 15% to 10% nitro helped. I plan on trying a head shim to quell the knocking. Anyone have a problem similar to mine? My next options were larger fuel tubing or a pump to get a more stable running engine. I can't think of anything else. Thanks.

    10% cool power
    14x6 prop
    stock muffler
    std fuel tubing

    (in reply to Flyboy Shady)
           Post #: 140

    RE: Lets take a poll on the FX 91 - 2/1/2004 8:14:16 PM   
    jaka


     

    Posts: 4627
    Joined: 12/11/2001
    From: Upplands Vasby, SWEDEN
    Status: offline     		Hi!

    Cannot think of OS making a bad engine! Never! At least I haven't seen any
    during my 30 years in