Another wasted evening with the OS 91FX

Another wasted evening with the OS 91FX (Full Version)

All Forums >> [Glow Engines, Gas Engines, Fuel & Mfg Support Forums] >> Glow Engines

Message

FLYBOY -> Another wasted evening with the OS 91FX (7/18/2003 7:25:07 PM)
I have been having the bubble problem on all my OS engines with rear needles. I replaced the O ring in the needle and took it out again. This has been going on all summer. There was no change, accept the bubbles are a bit less, and the engine quits sooner than it did before. Figure that one out. I have been flying for over 27 years and have never had an engine run this bad. My smaller FX engines do the same thing. The needle is very prone to changing the mix and if you screw it out farther, it doesn't seem to get richer, it just quits. There is like 3 clicks where it runs well for a few minutes, but then just dies. My last try will be to find a carb that will fit it with the needle in it. Does anyone know of one that will fit the 91FX??? I tried the carb from the .61 fs and it doesn't work. If that doesn't work, I am about to crush it and buy a super tigre or TT. If OS continues to put the needle in the back, I know two large clubs that will never buy them again. Just about everyone in both has tried to make this thing work. I emailed the Hobbico OS rep and he didn't even bother to respond. All of the other reps there have been great. If I owned Hobbico, I would fire this guy. I can't believe he didn't even take the time to answer with a stab at a solution. I know there are a lot of people having problems with these engines because you read it on here all the time. Sorry for the rant. If anyone has any ideas I would love to hear them. It ran good for about 2 tanks and I liked it when it worked. Would hate to drop back to a 61 or 75 but that is what I am going to have to do.

rcflyertim -> Another wasted evening with the OS 91FX (7/18/2003 7:46:07 PM)
I don't fly rear needle engines for many reasons. You just gave me another reason not too!! In all fairness, I guess this is a very acceptable way to do it and that many hours of R&D have gone into the process. It has to be a real good idea for safety sake, to keep the fingers futher away from the prop. Lots of luck and sorry that I do not have a great solution to your problem. I would send it back and ask them to replace it.

FLYBOY -> Another wasted evening with the OS 91FX (7/18/2003 7:52:00 PM)
Would like to, but have had it for about a year. I thought about sending it to them anyway and seeing what they charge to test it and see what they can do, but with 3 of them having the same problems, I figure I am ready to cut my losses and use a different brand. I have a new Webra Speed 61 in the box that will fly the plane well, or an old 61 SF that runs great. Wish I wouldn't have sold my Super Tigre .75. Will probably order another one. They run so well. I have an NIB 91 FX yet. Was going to put the pair in a Super Duelist I have. Not even a consideration now. Have to get a pair of ST .75s instead. Bummer. As you said, Lots of time spent in R and D. Too bad they didn't spend a little more and make something that works.

lucien -> Another wasted evening with the OS 91FX (7/18/2003 8:27:12 PM)
[QUOTE]Originally posted by FLYBOY Would like to, but have had it for about a year. I thought about sending it to them anyway and seeing what they charge to test it and see what they can do, but with 3 of them having the same problems, I figure I am ready to cut my losses and use a different brand. I have a new Webra Speed 61 in the box that will fly the plane well, or an old 61 SF that runs great. Wish I wouldn't have sold my Super Tigre .75. Will probably order another one. They run so well. I have an NIB 91 FX yet. Was going to put the pair in a Super Duelist I have. Not even a consideration now. Have to get a pair of ST .75s instead. Bummer. As you said, Lots of time spent in R and D. Too bad they didn't spend a little more and make something that works. I have also heard about an oversized O ring tower sells in packs of 2 for $15. Bad enough that they can't make it work, but then they rape you on a 50 cent O ring. Thats adding insult to injury. [/QUOTE] I've been following this for a while myself. I used to have a .61fx; it was mounted on a great planes ugly stick. It was the most flawlessly running motor I've ever owned and it never gave any problems either on the plane or on the bench. I'm about to purchase a 1.60fx for another project. My personal suspicion is a fuel flow problem (what else could it be) caused probably by excessive heating of the needle valve unit. This looks particularly troublesome on the .91fx, being as how, just eyballing a picture of the motor, the needle is _right_ there behind the head (and that motor probably runs hot anyway due to the large displacement/small crankcase size) and attached directly to the backplate of the motor by a surely very good heat-conducting flange. The .61fx probably doesn't have the problem to that great of a degree since it's a smaller motor (puts out less heat) and the needle valve doesn't appear to be right behind the head. That, combined with the completely open-air installation on my stick, is probably why I didn't have trouble with mine. On the 1.60fx, the needle appears to just be attached with that bolt on bracket which won't conduct too much heat to the valve. Anyway, it shouldn't be too hard to debug this problem, since overheating/leaning/quitting ain't rocket science to figure out. It can only be one of two things: not enough fuel or not enough air-cooling (or both). Has anyone tried sawing the needle off the backplate and mounting it somewhere away from heat? I think I heard of someone doing that in another thread and that fixed it. LS

FLYBOY -> Another wasted evening with the OS 91FX (7/18/2003 8:34:32 PM)
I thought about it, but haven't done it. Still a possibility but I would hate to do it.

pikebishop -> Another wasted evening with the OS 91FX (7/18/2003 8:57:07 PM)
you might try getting a K&B remote needle valve and mounting it on the firewall.

Hobbsy -> Remote needles (7/18/2003 9:56:34 PM)
Fox also makes a remote needle that has a great seal in it and I'm not the first to say that here.

DarZeelon -> OS.91FX (7/18/2003 9:57:19 PM)
It looks like OS made a boo-boo with this engine. It is incomplete, half-baked. Hoses and nipples need replacement by altenative larger sizes. It doesn't run out of the box. It isn't representative of OS's mostly quality products.

Ed Cregger -> Another wasted evening with the OS 91FX (7/18/2003 10:27:58 PM)
Just go to the Conley website, get their phone number, call them up and tell them you need a Perry carb for your engine. Problem solved forever.

rcflyertim -> Another wasted evening with the OS 91FX (7/18/2003 10:57:24 PM)
Flyboy, Even though your engine is 2 yrs old. I would still send it back for repair. They will still be able to look at it and make any repairs necessary. The only way they are going to make any changes is if people like you tell them it is a bad design!

Crash90 -> Another wasted evening with the OS 91FX (7/18/2003 11:10:14 PM)
I have owned 3 os 61fx engines. 2 of them ran perfect right out of the box. They both had the factory muffler. The 3rd one had a pitts style muffler and I had experienced the same problems that you are. I plugged up one of the pipes and everything was fine. Possibly you have a problem with tank pressure. What kind of muffler are you using?

Ed_Moorman -> FX Remote Needle (7/19/2003 12:04:29 AM)
I have one that I hated until I got a K&B remote needle valve assembly. It really works. I hack sawed the OS remote needle off my engine and threw it in the trash. Go to this URL http://www.modelengine.com/parts/61.htm, it's the K&B site. The part number is 92-9255, $15.95.

Sprink -> Not heat (7/19/2003 12:54:45 AM)
As far as I am concerned, while the engine does generate a lot of heat, this is not the cause of the problem. My own experience, supported on other threads is that if you have the bubble problem it is there from the start. The issue seems to be vibration. My theory is that the engine is causing the needle tip to vibrate enough to cause the fuel to foam as it passes. Mine now runs fine. I cut off the needle valve, and it is now mounted behind the engine on the firewall. The engine itself is on soft mounts. This isolates the needle valve from the vibration, and I no longer have the problem. I have never heard of this problem on any other OS, my 61FX, 32 SX and 25 LA have all run very well. :)

FLYBOY -> Another wasted evening with the OS 91FX (7/19/2003 8:18:03 AM)
Ok, here is what I have all done. I re-did the fuel system, no help, I put a new O ring on, no help, New plug, twice, no help. I put an OS .61 SF on and it runs great so it isn't the fuel system. I really like the idea of a K & B remote needle. I will order one and see what it does. I suspect that will help a ton. I think the problem is in the remote mounted to the back of the engine. Don't know if it is heat or vibration. I will get he K & B needle and let you know how it works. I would order a carb, but if I have to spend another $60 to make it work, I would rather sell it and buy a Super Tigre. I definately won't buy another OS with a rear needle again. This is bull. The new Stik flew really nice with the .61. Needs the added power though because I built it for 3D with the 91 in mind and it is heavier than a normal stik. Sweet bird though.

Flyboy Dave -> FLYBOY.... (7/19/2003 11:42:51 AM)
....what size is the mounting flange on the carb...? I don't own a remote needle carb....they suck.... ....sometimes literally.... :eek:

Andre -> Another wasted evening with the OS 91FX (7/19/2003 11:26:09 PM)
Wow! I'm having the same problem with my Dads OS .90 FX.We have also being in the hobby for over twenty years.The motor ran great for a few times then the air bubbles started.Of coarse I thought of a bad tank or fuel lines and maybe needle or O rings.I have being try to chase this problem down for a long time.If you get this remote needle and it works please post your results. Thanks Andre

jaka -> Another wasted evening with the OS 91FX (7/20/2003 12:17:50 AM)
Hi! You don't use a needle extension ...or use unbalanced Master airscrew props or cheap plastic spinners......? Regards! Jan K

FLYBOY -> Another wasted evening with the OS 91FX (7/20/2003 5:07:37 AM)
No cheap spinners, props or extensions. Thats not the problem. I have tried many props. All do the same thing. I am not home right now. I will measure it when I get back. I am going to order the K & B needle monday and try it. I hope that works. Also heard good things about an MVVS engine. Might look at one and give it a try. The 61 SF is nice, but I just want more power on the Stik.

rcflyertim -> Another wasted evening with the OS 91FX (7/20/2003 8:21:25 AM)
MVVS is a great line of engines also. I have 5 of them! I think you will like em!

sport10 -> Another wasted evening with the OS 91FX (7/20/2003 8:59:44 AM)
I believe that I would call Perry and get a carb from them that has the regular needle valve and is properly sized for this engine. That should help by elimating the remote needle all together.

Andre -> GMS .76 Carb will fit OS .90 FX (7/21/2003 11:45:31 PM)
I had a new GMS .76 Carb laying around just thought I would see if it fits.It fits very well just had to drill and tap both sides of the carb, for the mounting screws that O.S uses it was very easily done.I had a chance to test run it ,it ran in the high 10's rpm with a 14-6 APC on 15% Cool Power,the idle was great but a rain shower stopped us from fine tuning the low speed idle screw.The only thing that I may have to do is drill out the barrel for a little more air flow not sure if this is needed further testing will be needed.I'm very happy with the results so far and no bubbles.The barrel on the O.S is about 3/8" and the GMS is 23/64" not alot of difference so we'll see. Just tought I'd share my progress so far.I've talked to many guy's at the field they are having the same problems on their O.S also. My self I've gone away from the 2 strokes and fly YS 4 strokes,myDad is also switching over, his last 2 stroke is the O.S .90 FX. Happy Flying Andre

f2racer -> Another wasted evening with the OS 91FX (7/22/2003 12:12:59 AM)
[QUOTE]Originally posted by rcflyertim MVVS is a great line of engines also. I have 5 of them! I think you will like em! [/QUOTE] Don't have an OS 91FX, do have one of the newer MVVS 91 (has a standard carb as opposed to the butterfly carb found on some older models). Approximately the same weight and size as the 91FX. Runs awesome. Only about 4 tanks of FAI through it to date, but it turns an APC 14x6 over 11k and idles under 2k. Most amazing thing is that it's tremendously reliable. On my last flight of my Seagull Edge, the pitts muffler loosened it's bolts and fell off (rattling in the cowl), and the MVVS didn't miss a beat... With the exception of the sound and a slightly uneven idle, I never would have known something was "wrong". It ran so well that I even flew straight up vertical without the engine leaning any more than it did with the muffler attached. Now there's the sign of a great engine. I remember loosing the muffler on my TT GP-42 which resulted in immediate dead stick, yet without the muffler, I actually flew at least 6 landing patterns before finally landing with the MVVS. Can't wait for the engine to be really broken in, I plan on putting a 15x6 prop on it to see what it'll really do!

ShempHoward -> Another wasted evening with the OS 91FX (7/22/2003 1:29:42 AM)
This is a truly puzzling phenomenon. I have seen some 91FX's that have run perfectly from day one right out of the box, then I know of one that ran perfectly for about a dozen flights then started acting up followed by several that did not run properly at all right out of the box. The problems seem to range from needle valve "O" rings to a problem with the neede valve casting being oversize to poor nipple fitttings. The easiest solution seems to be Ed Moormans answer - the K+B remote needle. I have one of the very early models standing by NIB and have the "alleged" replacement "O" rings for the needle but my spare NIP OS 7d carb (90FSR/108 FSR) is probably going to be the best fix of all - I hope.

sport10 -> Another wasted evening with the OS 91FX (7/22/2003 4:15:51 AM)
A power comparison betweent the MVVS .91 and the OS .91FX would be interesting. I am considering the MVVS .91 for the new YAK profile from Ohio Models.

f2racer -> Another wasted evening with the OS 91FX (7/22/2003 5:55:21 AM)
[QUOTE]Originally posted by sport10 A power comparison betweent the MVVS .91 and the OS .91FX would be interesting.[/QUOTE] I'd like to see a comparison as well. The only 91FX that I've seen was on a pretty lightweight UltraStick 60. Pulled it fine, but it took forever for the owner to tune it and was prone to deadsticks (good thing it was on a light model which could float down to a landing). My Edge (with the MVVS) has unlimited vertical with a 14x6 prop (and a pitts muffler), but I'm guessing the Edge is a bit heavier than the US and has significantly less wing area so I'm hoping that I don't deadstick any time soon. Should have even better 3D performance with either a 15x6 or 16x4 prop. What are peoples 91FXs turning with a 14x6? From what I understand, this prop is a tad too small for the MVVS, it's actually "tuned" for 9.5-10.5k, I'll get some additional numbers with a 15x6 prop soon. As mentioned, I ran one tank on the ground slightly rich and took to the air. The engine has been completely reliable... I bought the MVVS 91 because I've gotten great mileage outta a 40 and 49. Both have great power, low idle, crisp transition, run on cheap FAI fuel, and definitely stand out (you'll never mistake a MVVS for an OS or clone). So far I've been very pleased with the 91.

Page: [1] 2 3 4 5 6 7 next > >>

SITE MAP! : : FORUM RULES

© 2001 - 2007 24-7 RC, LLC, all rights reserved.

0.203125