Rendegade

Hmm, no comments to my queries.

I tell you what. I'll give you all my FX's if one of you will hand me a NIB 40 FSR.

Sound like a good idea?

N1EDM

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Hi Renegade,

I wouldn't give up those FX's so easily. Did you check inside the tank for perforated tubing or a nick/slit in the silicone tubing inside the tank?

Just a thought...

Bob

N1EDM

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Geesh, you guys can't tell me that you've never taken a 91FX 4-Stroke apart before...

I'd love to give this engine a 'go' if I can find out how to time the cam...

Anyone???

Thanks,

Bob

earlwb

Sorry, I would, but I haven't taken one apart before.

As for the valve cover gasket, some engines have it some don't. But it is easy to make one out of card stock using a fresh X-acto knife blade.
You can trace the outline using the valve cover, then measure the inside to be about as thick as you want it to, and then cut the inside out before you cut the outside of the gasket.

excerpt from the OS site http://www.osengines.com/faq/product-faq.html#q15 :

N1EDM

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Thanks a lot, Earl. That's what I was looking for.

I appreciate it!!

Bob

Rendegade

Checked, pressure tested, everything is spot on. More to the point after some messing around we found that the bubbles would only appear above half throttle. and would only appear in the tube between the NVA and the carb nipple.

I'm starting to thing it's vibration related, but just can't put my finger on it.



Now, for another curly one...

Another 46fx I have, was put into the club trainer, and loe and behold it would run sweetly for about 3 minutes and then just fart out. Tried different fuel, new glow plug, sealed the NVA, cleaned the carb, checked the tank plumbing, even went to the point of putting a 4D carb on it (one that I trust) and sure enough every flight would be a dead stick in three minutes time. You could set your watch by it.

I ended up in a fit of rage putting an A5 plug in it from my 160fx which detonated heavily on a #8, and tried one last time.


The engine started, and didn't stop for the next 20 minutes. As a matter of fact that aircraft managed to get a good 100 minutes air time that day and started first flick, and drained the tank completely every time!

Who would have thunk that a cold plug on 7% nitro fuel would make all the difference? not me!

hugger-4641

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I've had similar experiences with .46fx's and .46la's as well as some other brands.Changing to anA3 is one of the first things I do now when I'm having trouble withdead sticking andI can't nail down an air leak or fuel problem. After I'm certain everthing else tuned and working properly, then I'll go back and try a #8. One of my .46fx's is so sensitive with a #8 plug thattwo clicks too far either way on the hs needle will cause it todie on throttleup or cause it to dead stick whenI throttle back down to idle. I currently own three .46fx's, three .46ax's, one 55ax, one75ax, but that old .46fx is the onlyone that is so sensitive. It is just as stong asmy other .46's and they all run fine on a #8, Idon't knowwhy it's different, but it is.

N1EDM

My Feedback: (2)

Did you get a chance to look at the needle valve itself (is the tip bent, dirty, etc.) and its socket (once found a piece of grass in one of mine).

Just a thought...

Bob

Rendegade

Everything is clean as a whistle. If I have odd running engines the NVA is the first thing to be cleaned.

Flynsail

My Feedback: (4)

In going thru the depth of my stores I new never run OS eng with muffler in it original box.
The engine has simply a 10 on the exhaust side and standard OS markings on its bulging left side.
The box has the label of OS 10F SRS While I have seen the FSR reference I can't find what the "S" stands for and/or what the engine's value is.
Anyone?
Thanks

fordman1

The S means it was a non throttled C/L engine. They still use that designation at OS. It is  a 10FSR-S. No carb and they cost more that a carburetted engine. Go figure. A carb will cost over 20 bucks.

N1EDM

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Hi guys,

Well, I reassembled my 91 Surpass and have noticed that there isn't that much compression. I removed the head and poured some after-run oil on the piston and let it set overnight. Nothing seemed to leak past the ring, so I'm thinking and hoping that the ring/cylinder/piston are OK.

The only thing I never tore down was the valves, so I tried that. They're held on with split washers held in place with a collet. For whatever reason (hardened caster, whatever) I can't seem to push the cam down to remove the split collets and take the valve assembly apart for inspection.

If I push down on the collet, everything goes with it, even though the valve is held in check to keep it from moving.

Has anyone else ever had this problem? And if so, how did you get over it. I have an idea for a tool but it would take time to fabricate. I was wondering if there was a quicker method.

Thanks,

Bob

rcdude7

My Feedback: (264)

The keepers can be tight and/or stuck from castor varnish. Push down on the retainer evenly to get it to snap loose, maybe use a small socket or something and do this in a bag so you don't loose any of the tiny parts.

N1EDM

My Feedback: (2)

That socket wrench is a great idea... or a nut driver. I hadn't thought of that. Thanks.

And a major 'Yes' to doing it inside a bag.

Thanks,

Bob

EyeflyRC

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OS 46 AX engine problem. Yesterday I flew my Hanger 9 Ultra Stick 40 with a side mounted OS 46 AX that I bought used but in good condition. The engine ran fine in the air but when I landed it flamed out and I had to pick it up from the runway. Filled the tank again and went to start the engine and there was no compression, none at all. Bearings were smooth, no dirt in the engine, just no compression and of course it would not start. Had other planes to fly so I decided to check out the engine when I got home.

At home I took the muffler off to look at the piston and it was near new in appearance. Cylinder wall looked to be in good condition. Put some oil in the cylinder, still no compression but sounded like air was escaping somewhere. Checked the cylinder bolts and they were all tight. Took out the glow plug and put my finger over the hole and felt some compression. Examined the glow plug closely and it looked like I could move the stem slightly side to side. Installed a new glow plug and compression was back like new. The culprit was a blown seal on the glow plug. Problem solved.

landeck

My Feedback: (1)

EyeflyRC, I had the identical problem last week with a Fox .74 Eagle IV in an Escapade 61. The blown seal on the glow plug was the problem but it manifested itself in a different way. The plane went dead stick in the air after about 5 minutes flying. On the ground the engine started fine and seemed to run OK so I took it up again and had another dead stick. On the ground again it started but I had difficulty setting the high speed needle. Finally it seemed set and off I went. This time the engine seemed to oscillate between OK and lean. I landed without it dying. Back on the bench I happened to touch the stem of the glow plug and it wiggled. I replaced the plug and all was fine.

BTW, where do you fly in Atlanta? I fly out at the GMA field 2-3 times a week.

Bruce

EyeflyRC

My Feedback: (147)

Landeck. Now that I think about it, I had that engine in a Venus 40 that I crashed due to pilot error some time ago. It was on the third flight of the Ultra Stick 40 when the seal blew. Perhaps it had been damaged in the crash.

I fly at Bartow County Model Aviation's (BCMA) new field off Lake Altoona Rd at Emerson, GA. It is just a 30 minute drive from my home in Sandy Springs. I take I-285 and I-75 to get there. Nice bunch of guys at the club. I particularly like the fact that the field is positioned so that the sun is at out back at all times and I can sit in my lawn chair in the shade under the tailgate of my Minivan at the flight line and fly in utmost comfort.

I am also a member of GMA but don't fly there very often because it takes twice as long to drive there.

Would you like to try out our field? Let me know and we can go there together during the week.

Andrew
404 255 0829

landeck

My Feedback: (1)

Andrew, we know each other. In fact you were over to my house a couple of years ago. Both the Bartow and GMA fields are about the same distance time wise from where I live. Also I like the facilities at the GMA field and there is a good group of guys on weekdays that I enjoy flying with. That is why I like flying there.

Bruce

N1EDM

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Well, I've been playing around with that OS.91 that I've rebuilt... but it still feels like there is hardly any compression. Lemme see. Here's what I did. Can you guys think of anything else?

General cleaning
Lapped the valves (I can't hear any hissing from the valves when I rotate the engine)
Changed all bearings
New head gasket
New carb intake gasket
New ring
Verified that the cam timing is good (at least, from what I can see)
Set the valves at about .002

I still get hardly any 'pop' when I flip the engine over with a prop on it. I can't think of anything that I'm missing, but I wonder if you guys can?

Any thoughts???

Thanks,

Bob

Rendegade

you may have a stuck ring. I had a similar problem in a ST-90 that was caused by the ring being stuck/glued to the recess in the piston. All it too was a bit of a clean and ring sprung back out and all was well.

Let us know how you go.

EyeflyRC

My Feedback: (147)

Put a few drops of castor oil in the cylinder through the glow plug hole and check to see if this brings up the compression to normal. If it does, the ring probably has not seated in the cylinder,
especially if you did not clean out the glaze in the cylinder walls before you installed the ring. The easy solution would then be to run the engine on the bench until the ring seats itself. Use fuel with castor oil in it for this task. If you only have fuel with synthetic oil, add eight ounces of castor oil per gallon to it. When the ring is seated and compression is normal, go back to your regular fuel.

The hard way would be to disasemble the engine again and scour the cylinder walls with fine steel wool and plenty of soap and water. Use a circular motion when you do this to get a cross thatched look in the cylinder. There are blogs on RCU on how to do this in great detail when installing a new ring.

Hope this helps.

N1EDM

My Feedback: (2)

Thanks EyeflyRC. I did put oil in the cylinder - a few drops of Bakers AA that I had, just to keep the ring from scoring on a dry wall. But you are right, I did not score the cylinder. I can't imagine that that would bring up a lot of compression, perhaps just marginally.

I'm really at my wits end with this engine. I thought I had it licked. I can't hear anything leaking (valves, around the plug or head, etc.) but she is not building up compression. I'll scour the cylinder and try to see if I can get her running.

I usually don't have a problem with engines.... I'd sure like to get this one running.

Thanks again for the reminder,

Bob

earlwb

Niedm, I had the piston ring get stuck on several engines over the years. I just recently replaced the dykes ring on a Irvine .61 that was stuck and caused the compression to vanish. it now works good once again.

EyeflyRC

My Feedback: (147)

Niedm,
If the ring was properly installed the castor oil should have sealed the ring enough to start the engine even if you did not clean the glaze off the cylinder walls. If you tried starting it and were unsucceful due to lack of compression, I would suspect that the timing is set incorrectly. You would not hear any air escaping if a valve is open on the compression stroke. A possible way to check this is to take the valve covers off and watch the movement of the valve lifters as you rotate the piston. Both valves should be closed tight on the compression stroke and you can check this by being able to insert your feeler gauge in both rocker arms on the compression stroke. If you cannot, then that valve is partially open and is the cause for lack of compression due to improper timing.
Andrew

rrengineer

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