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O.S. Max 65AX

Old 07-23-2017, 03:56 AM
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boompa61
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Question O.S. Max 65AX

I have a new 65AX that is pre-detonating, this causes it to kick back severely. Thought a couple of times I was going to loose the rubber end to the chicken stick. I have used O.S. for some time and never encountered this problem. It starts backwards the majority of the time. It is making a noise like the old car engines when they were out of time, a metal rattle. It has probably two hours run time total. There is a small exhaust leak indicated by a small dark area just above the muffler. It is tight but I haven't tried a sealer yet. My reasoning was it they wanted you to use it they would tell you, but have to do something there. Have I missed something here? Another member has the same new 65 and is experiencing the same issues. Just thought I would see if anyone else is having these problems. To avoid the backward starts and kick back I am starting off my flight box and having a buddy hit a power to on after I get it spinning with my starter. This works well but the metal rattle has us concerned. Anything anyone can pass on to us. Boompa here.
Also on a different note I am considering going gas or possibly glow/gas. Tired of cleaning oil from everything; any suggestions. I see O.S. has a 15 glow/gas that bolts up same as the 65 AX glow fuel, how are they?
Old 07-23-2017, 04:27 AM
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aspeed
 
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It could maybe use a head shim, or less nitro? It might be still tight which could make the noise as it sticks on top, or preignition.
Old 07-23-2017, 04:34 AM
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1QwkSport2.5r
 
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Starting backwards often means it's over primed/nearly flooded.
Old 07-23-2017, 07:53 AM
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C-4 Good one. When I went back and read the manufactures instructions on the silencer (muffler to me). Go ahead and let me have it, I can take it.
So you say over primed. Could this also be low end too rich? I hesitated to lean out the low end until I had some more run time. Leaned out low end a little but because its new I was holding off on that. Until that change the factory setting hadn't been changed on low end. This shim mentioned, just an addition head gasket do the trick. or is there a part for this? Is this something you have tried yourself. Not doubting you just curious to see personal experience and results.
Old 07-23-2017, 08:26 AM
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Is the engine mounted upside down?
Old 07-23-2017, 08:29 AM
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Yes, just another head gasket. I have done it many times to adjust for different propellers and other variables. A smaller propeller would like higher compression than a larger load one. Normally I take them out to go faster, but you get to a point where it is overcompressed (as yours seems to be) then you have to add them. If you blow plugs, then you would normally add a shim too, as well as richen it up a bit on the high speed needle. As to your first post, A gas motor has more things to go wrong, Glow is much more simple, the main reason I like them.

Last edited by aspeed; 07-23-2017 at 08:33 AM.
Old 07-23-2017, 02:00 PM
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I have my doubts many of the AX engines need a head shim out of the box to run the fuels commonly used (up to 15% nitro typically) these days. I would be only priming the engine one or two flips (with carb choked) after fuel reaches the carb.
Old 07-23-2017, 02:03 PM
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boompa61
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No. straight up.
Old 07-23-2017, 02:06 PM
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Ya, maybe it is overflowing into the muffler, or the tank is too high or something.
Old 07-23-2017, 02:25 PM
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Really appreciate you taking time to help. I will watch the priming to make sure not to over do it. Then if after the engine is broken in I am still experiencing problems I will add the shim. To answer the question from someone and I don't know how this thread thing works exactly, I have the motor mounted straight up, and I am using 15% cool power. It is what the hobby shop carries. Can't afford shipping on that stuff. I appreciate all comments. Thanks guys. Yes I started back flying glow nitro because of the dependability and ease of use when it comes to adjusting and running engines. As you probably deduced I am not a natural mech. However the oil is getting old. Would there be any additional problems mounting the motor 90 degrees from straight up? I could get the exhaust away from the plane further with the exhaust mounted down. By the way this is on a 60 size stik, the only change I see would be the throttle. Shouldn't be that big a challenge changing the throttle. I kind of wanted to get all engine problems out of the way before adding additional unknowns into the equation.
Old 07-23-2017, 02:44 PM
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When I fuel I remove the line at the muffler and let it flow into a catch bottle. The tank according to the specs should actually be a little higher but on a almost ready to fly stik not a lot of room for change there. I have probably been guilty of over priming a bit but didn't consider this the problem because the engine will fire and run (backwards) and I have to kill to restart. And the pre-ignition happens then also, after the motor has run. I haven't noticed any problem siphoning. Changing to power starts from hand starting has simplified things. Maybe I need to fly the summer out and find out if the motor is just needs more run time. The shim is new to me so I will keep this in mind going forward.
Old 07-23-2017, 03:56 PM
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jrf
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Mounting the engine sideways (90 degrees from straight up) is a very good idea. It minimizes the oil on the airframe, it puts the carb at the centerline of the tank, which is where it will run most consistently, AND any excess prime will run out of the carb instead of into the crankcase. You will need to re-tune it though. It will be a little richer on both needles.

Sorry if this is a repeat, but if you are filling the tank through a T fitting in the tank-to-carb line without closing the needle valve or pinching off the line, that will flood the engine and cause the problems you have experienced.

Another thing that will cause an engine to start backwards is to flip it too slowly, or to have the prop set in the wrong part of the piston travel. The prop should be installed on the engine so that the piston just starts to come against compression when the prop is at 45 degrees. Starting the flip there means that you will reach the highest flip speed as the engine reaches top dead center.
Old 07-23-2017, 04:11 PM
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Originally Posted by boompa61 View Post
I have a new 65AX that is pre-detonating, this causes it to kick back severely. Thought a couple of times I was going to loose the rubber end to the chicken stick. I have used O.S. for some time and never encountered this problem. It starts backwards the majority of the time. It is making a noise like the old car engines when they were out of time, a metal rattle. It has probably two hours run time total. There is a small exhaust leak indicated by a small dark area just above the muffler. It is tight but I haven't tried a sealer yet. My reasoning was it they wanted you to use it they would tell you, but have to do something there. Have I missed something here? Another member has the same new 65 and is experiencing the same issues. Just thought I would see if anyone else is having these problems. To avoid the backward starts and kick back I am starting off my flight box and having a buddy hit a power to on after I get it spinning with my starter. This works well but the metal rattle has us concerned. Anything anyone can pass on to us. Boompa here.
Also on a different note I am considering going gas or possibly glow/gas. Tired of cleaning oil from everything; any suggestions. I see O.S. has a 15 glow/gas that bolts up same as the 65 AX glow fuel, how are they?
I wish you could share a short video of the engine running. New ABC or similar ringless engines need to come up to a temperature where the pinch at compression is relieved. You may be running too rich. You won't hurt the engine to bring it up to maximum rpm, then bring it down where you can audibly tell the rpm's have dropped.If you have a tach, lower the peak rpm's 300-500.
Also, I would run a low load prop. Try a 12-6 and see if the knocking is reduced. If you are using 15% fuel, buy or borrow some 5% or 10% and give it a try. One other thought...Are you running extra castor? Too much oil can cause similar issues with high compression engines.
Old 07-23-2017, 06:17 PM
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1QwkSport2.5r
 
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OS engines have minimal pinch. Hardly a concern here - OS engines are basically flyable right out of the box.
Old 07-24-2017, 05:52 AM
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No T, have a three line tank set up. Fill / ex / carb. Thanks for your info on the engine mount, am considering this as an option. The prop is just less than 90 counter cc. So I will improve the angle a little. Once the engine is running, it runs well it just has a different sound. Like metal rattle. It kind of comes and goes, sometimes it is very noticeable. As I said one of the other members just purchased the exact engine and it is doing the same. So the fuel is different. I opened this gallon about 45 to 60 days ago. The rain has kept us on the ground a lot here. Using a wooden prop Zoar 13x6. The other fellow is using a master airscrew 13x6. No on the extra castor. And fly out of the box. That is basically what I have done. The other fellow went through the break-in process. I know I am answering everyone in one reply sorry. I get lost in all the threads.
Old 07-24-2017, 06:26 AM
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Do you have the engine tuned to run a clean two-stroke on the top end and a good low idle quality and smooth transition to high throttle?
Old 07-24-2017, 07:56 AM
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Regarding the "rattle". I had a Magnum 52 that did the same thing. Adding a head gasket helped but did not solve the problem. Running it on 5% nitro pretty much made it go away. Maybe OS has decided to build their engines to run on lower cost fuels. I buy 5% fuel for about $15 per gallon. (Europe uses mostly 0 nitro fuel.)
Old 07-24-2017, 07:58 AM
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Originally Posted by jrf View Post
Regarding the "rattle". I had a Magnum 52 that did the same thing. Adding a head gasket helped but did not solve the problem. Running it on 5% nitro pretty much made it go away. Maybe OS has decided to build their engines to run on lower cost fuels. I buy 5% fuel for about $15 per gallon. (Europe uses mostly 0 nitro fuel.)
I have my doubts OS is building their engines for lower Nitro fuels - especially those being imported to the United States.
Old 07-24-2017, 08:18 AM
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Hi!
Agree! The compression is not the problem if using 0-15% nitro fuel.
As usuall with all ABC, AAC or ABN engines . Bring it up to full speed as soon as you has started it! -That's important so the brass (alu) cylinder can expand properly! never ever run the engine "slobbering" rich! -You only do this with old type Mechanite (iron cylinder/piston) engines.
Old 07-24-2017, 09:32 AM
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Originally Posted by 1QwkSport2.5r View Post
I have my doubts OS is building their engines for lower Nitro fuels - especially those being imported to the United States.
The cost of fuel is stated as one primary reason that so many modelers are switching from glow to gas. OS has every reason to offer engines that use less expensive fuel, as they do in Europe. The OP says that two brand new OS engines make an inconsistent metallic rattle while running and at the same time give every indication that they are running rich. Do you have another suggestion as to the cause?
Old 07-24-2017, 12:49 PM
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Originally Posted by jrf View Post
The cost of fuel is stated as one primary reason that so many modelers are switching from glow to gas. OS has every reason to offer engines that use less expensive fuel, as they do in Europe. The OP says that two brand new OS engines make an inconsistent metallic rattle while running and at the same time give every indication that they are running rich. Do you have another suggestion as to the cause?
OS makes piles of gasoline engines. The people who want to use cheaper fuels use gasoline engines. Glow fuel at $15-40 per gallon depending on locale or $3-7 per gallon for gasoline depending on locale and oil used. Not a complicated idea to grasp the concept of. A metallic rattle to one person may only be a peaked out mixture setting to another. Maybe it's the muffler. It's not uncommon for muffler baffles to be loose, so there's another possibility.
Old 07-24-2017, 01:00 PM
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Hi!
The "rattle" comes from the crank as it moves forward and backwards in the crank case,this is due to the engine running rich. Plain bearing always do this when set too rich!
Old 07-24-2017, 01:31 PM
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jrf
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Originally Posted by jaka View Post
Hi!
The "rattle" comes from the crank as it moves forward and backwards in the crank case,this is due to the engine running rich. Plain bearing always do this when set too rich!
The 65 AX is not a plain bearing engine.
Old 07-24-2017, 01:32 PM
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Jan - the OS 65AX is a twin ball raced engine, not a bushing engine.
Old 07-24-2017, 07:48 PM
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I run 15% Morgan Omega in my 75 AX with no problem and in the 65 ax SB ok as well
Power is my goal and the 75 is a beast in my 60 stik
i think you are turning to much prop with the 13/6 and that is your detination problem
i use a 12/6 APC on my 75
Try a 12/6 or 12/5
Many reduce the size of a prop by one inch to break in a glo engine
Use a tach and prop the engine to run at the max RPM recomended by OS on the high end

Flying glo for 23,years

Enjoy

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