OS 91 fx tuning problem! HELP!!!!
07-18-2009 | 05:29 PM
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From: , SC
OS 91 fx tuning problem! HELP!!!!
I recently acquired a .60 size stinger with a os 91 fs max (60F carb, high speed and low speed needle). This is my third airplane and I'm having some trouble tuning it. I've been spoiled by having the relatively easy to tune LA .40 and .46's on my previous planes. Before I ask this question, let me point out that I've referenced all available guides in tuning, but I just cant seem to get it dialed in. It starts fine, but when I try to give it full throttle, it sputters and dies. Even when I seem to get it to a point where it will run, the thottle is very sluggish. Any suggestions on where the high speed and low speed needle should be set (I've tried the air blowing method)?
Thanks!
Thanks!
07-18-2009 | 05:36 PM
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From: Grants Pass,
OR
RE: OS 91 fx tuning problem! HELP!!!!
Follow the instructions included with the engine for adjusting the needle valves. O.S. is very clear on how to do it. If you don't have the instructions you can get them at O.S.'s website.
07-18-2009 | 06:05 PM
#3
RE: OS 91 fx tuning problem! HELP!!!!
it is almost impossible to tell without seeing the engine but it sounds like it is rich on the low end and possibly the high speed too. lean it in very small increments and re-check.
07-18-2009 | 06:09 PM
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From: Orchard park,
NY
RE: OS 91 fx tuning problem! HELP!!!!
ORIGINAL: usafloadc17
I recently acquired a .60 size stinger with a os 91 fs max . . .
I recently acquired a .60 size stinger with a os 91 fs max . . .
07-18-2009 | 06:15 PM
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From: , SC
RE: OS 91 fx tuning problem! HELP!!!!
Sorry that was a typo. it is an fx. no, I was not aware the old models had a problem with the valve. What's odd is the gentleman I bought it from had no problems with it. I've set it to the factory setting of 2 turns in on the high speed and 2mm at full throttle on the low speed. I flew it earlier today and it wouldn't give me anything higher than half throttle. Also shuts off in a climb.
07-18-2009 | 06:42 PM
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From: FrederickMD
RE: OS 91 fx tuning problem! HELP!!!!
Just because its at the factory settings doesn't mean its the correct setting for your set up. That's just a starting point. Get the directions for tuning the low end from the factory manual and follow them to the letter. Remember to readjust the high speed needle after every low speed needle adjustment.
Brad
Brad
07-18-2009 | 10:14 PM
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From: Huntersville,
NC
RE: OS 91 fx tuning problem! HELP!!!!
ORIGINAL: usafloadc17
.....it wouldn't give me anything higher than half throttle.
.....it wouldn't give me anything higher than half throttle.
We finally figured out what the prob was when I was able to turn the high end needle almost completely out and it still run ok. The lack of smoke was also a huge indicator. Should have been super rich and blowing lots of oil but it wasnt.
After richening the low end a 1/4 turn at a time we finally got the high end needle to respond. From there we then fine tuned the low end an 1/8 turn at a time.
Good luck,
James
07-19-2009 | 01:30 AM
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From: Warialda NSW, AUSTRALIA
RE: OS 91 fx tuning problem! HELP!!!!
ORIGINAL: usafloadc17
I recently acquired a .60 size stinger with a os 91 fs max (60F carb, high speed and low speed needle). This is my third airplane and I'm having some trouble tuning it. I've been spoiled by having the relatively easy to tune LA .40 and .46's on my previous planes. Before I ask this question, let me point out that I've referenced all available guides in tuning, but I just cant seem to get it dialed in. It starts fine, but when I try to give it full throttle, it sputters and dies. Even when I seem to get it to a point where it will run, the thottle is very sluggish. Any suggestions on where the high speed and low speed needle should be set (I've tried the air blowing method)?
Thanks!
I recently acquired a .60 size stinger with a os 91 fs max (60F carb, high speed and low speed needle). This is my third airplane and I'm having some trouble tuning it. I've been spoiled by having the relatively easy to tune LA .40 and .46's on my previous planes. Before I ask this question, let me point out that I've referenced all available guides in tuning, but I just cant seem to get it dialed in. It starts fine, but when I try to give it full throttle, it sputters and dies. Even when I seem to get it to a point where it will run, the thottle is very sluggish. Any suggestions on where the high speed and low speed needle should be set (I've tried the air blowing method)?
Thanks!
G'day Mate,
What size prop, type of glow plug, nitro content of fuel.
Have you checked the fuel tube inside the tank?
Make sure it is rich enough at the top end to increase slightly in revs, when the nose is pointed up, at full throttle, if so then it should be rich enough to keep running in the air.
07-19-2009 | 06:54 AM
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From: Orchard park,
NY
RE: OS 91 fx tuning problem! HELP!!!!
The needle valve should look like the current offering:
http://www3.towerhobbies.com/cgi-bin...&I=LXBY47&P=RF
If you have the older metal variety it should be replaced either with the plastic one or suitable substitute.
http://www3.towerhobbies.com/cgi-bin...&I=LXBY47&P=RF
If you have the older metal variety it should be replaced either with the plastic one or suitable substitute.
07-24-2009 | 06:42 AM
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From: , SC
RE: OS 91 fx tuning problem! HELP!!!!
I think I figured it out. I replaced all the lines which seemed to help, and I also noticed that the 3rd line (fill line) was leaking when under pressure. I adjusted the fill cap to make a tighter fit and everything seems to be in order. I haven't flown it yet, but the high speed needle is a lot more responsive. Thanks for all the help.
07-24-2009 | 10:49 AM
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From: Ashland,
MA
RE: OS 91 fx tuning problem! HELP!!!!
I was discussing this engine with someone at my field who mentioned an extensive period of trouble tuning his and said removing the baffle from the muffler finally resolved the problem. I've never owned one...
Obviously this is completely anecdotal advice…
If you try it let us know the outcome....
Obviously this is completely anecdotal advice…
If you try it let us know the outcome....
07-24-2009 | 12:02 PM
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From: Huntersville,
NC
RE: OS 91 fx tuning problem! HELP!!!!
Hi,
I own two 91 FX's and the first engine I was able to tune no prob with the baffle in the muffler. The only downside I found with the baffle was that it limited rpm slightly. Maybe 500 rpm or so if I remember correctly.
The second 91 I got just this year and I removed the baffle before I even got the engine mounted on the plane.
Let me add also that the 91 at full throttle can drink an ounce of fuel / minute. So you need at least medium ID fuel tubing for proper fuel flow. Be careful with tanks that come with small ID pick up lines.
Cheers.
I own two 91 FX's and the first engine I was able to tune no prob with the baffle in the muffler. The only downside I found with the baffle was that it limited rpm slightly. Maybe 500 rpm or so if I remember correctly.
The second 91 I got just this year and I removed the baffle before I even got the engine mounted on the plane.
Let me add also that the 91 at full throttle can drink an ounce of fuel / minute. So you need at least medium ID fuel tubing for proper fuel flow. Be careful with tanks that come with small ID pick up lines.
Cheers.
07-24-2009 | 02:38 PM
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From: Denver, CO
RE: OS 91 fx tuning problem! HELP!!!!
OP - are you able to get it to idle smoothly and then it sputters when in the transition to full throttle? If so, that sounds like your low end is a little rich. Try leaning it out by 1/16's of a turn. If you go too lean, it should abrubtly die out when going WOT.
If on the other hand it's still sputtering once you get to full throttle, that sounds like you just need to lean out the high end a bit.
This is how I tuned my OS 46fx. It now runs like a swiss watch.
If on the other hand it's still sputtering once you get to full throttle, that sounds like you just need to lean out the high end a bit.
This is how I tuned my OS 46fx. It now runs like a swiss watch.
07-24-2009 | 04:41 PM
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RE: OS 91 fx tuning problem! HELP!!!!
Replace all the lines, make sure the 3rd line (fill line) isn't leaking when under pressure. Adjusted the fill cap to make a tighter fit and everything will seem to be in order. The high speed needle should be a lot more responsive.
Hope this helps...
Hope this helps...
07-25-2009 | 02:49 AM
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From: haiphong, VIETNAM
RE: OS 91 fx tuning problem! HELP!!!!
It's important to understand that there is a reputation for glow-engines to be difficult to tune. This is a common error in thinking. With a little bit of know-how, tuning a glow engine can really be a simple, pain-free process. People that don't properly understand the basics can easily become frustrated by what should be a simple, straightforward process. Here's how you do it:
<h3 class="post-title entry-title">Glow Engine Tuning</h3>
<h3 class="post-title entry-title">Glow Engine Tuning</h3>
