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Ever taken apart an OS 46 ax ?

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Ever taken apart an OS 46 ax ?

Old 06-07-2016, 12:18 AM
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Default Ever taken apart an OS 46 ax ?

Last Saturday i was flying my sky raider and was doing a spiral dive but when i let off the aileron stick and pulled back on the elevator to bring the nose back up the strangest thing happened. Nothing !!! My little sky raider drilled itself into the dirt.
I took the mess home and during the autopsy discovered that my receiver was no longer listening to my transmitter. No response at all to the control inputs. Tried another receiver and still nothing. Tried another transmitter and it worked fine. I guess my old futaba conquest had transmitted its last signal. (wish it woulda done that during the pre flight). So any how the field i crashed in was plowed up and the dirt wasn't to awful hard so I don't think i bent the crankshaft. . But the motor was running about 1/3 throttle when it hit and i washed allot of dirt out of the carb. I pulled the back cover off the motor and discovered a bunch of what must be dirt diluted with glow fuel all over inside so i am assuming the motor inhaled a gob of dirt before it died. Im thinking i need to pull it all apart and clean it up. (Bearings and such).
I have never actually dissembled one of these motors and was wondering if anyone could give me any tips on how to do so. I already have one problem, i went to pull the bolts to remove the head and naturally my allen wrench stripped. Is there such a thing as an allen wrench that is as tough as the allen screw? Any advice would be much appreciated....
Dave
Old 06-07-2016, 03:34 AM
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I did the same thing with my .55AX. I had to buy a new crankcase n muffler. Disassembly is not too difficult. Main thing is keep orientation of the parts for reassembly. Picture shows old on left n new on right. My old engine was pretty new as you can see in the picture.

Use a good quality wrench. Bolts should remove easily.

Here is is a 2 part video that will help.

VIDEO
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Old 06-07-2016, 10:48 AM
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Thanks ET, thats just what I needed... Dosent look to hard.
Old 06-07-2016, 10:51 AM
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For some reason i get an error on the 2nd video but i think i can put it back together the way it comes apart. No need for assembly lube on the bearings right? Just glow fuel?
Old 06-07-2016, 11:27 AM
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Dave, There are many tricks to disassembling an engine without damaging it. Tight cylinders, and bearings come out much easier if the case is heated. Another trick to get a tight sleeve out is to place a copper glow plug washer in one of the cylinder ports, and turn the engine over CAREFULLY and the piston will push the sleeve out. The best advice is to get help from an experienced modeler. There are a lot of soft Allen wrenches sold in this hobby, but it possible that you had an SAE wrench for a 4-40 screw, instead of the correct metric wrench. They are very close in size. The Chinese tools sold by Harbor Freight, and Northern Tool are much better then they were only a few years ago, and a set of small SAE and Metric wrenches can be bought for less then $10.00.
Old 06-07-2016, 03:24 PM
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Thanks for the reply Greg,
Hopefully i wont have to take the sleeve out. Unless its all scratched up i will just clean it good. Its mainly the bearings i want to get out and make sure there is no dirt in them. So I guess as long as i remember which way the bearings were installed and put them back in the same way and do the same for the piston and rod i guess it should be ok. (hopefully) I believe you are right about the heating up the motor also. I remembered that I changed the head on that motor a while back and re-tightened the head bolts after running the motor. I am guessing that's why i am stripping allan wrenches. I need to heat the motor so they will pop loose and also to remove the bearing. At least that's my plan so far. Of coarse i will remove the carb first. Im gonna wait a few more hours before i dig in to it and see if any one else has some input also.
Thanks for the response....
Dave
Old 06-07-2016, 05:29 PM
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I don't think you will get the bearings out without getting the sleeve out first. I would leave the bearings in and just flush them well. Blow with an air hose and then oil.
Old 06-07-2016, 05:36 PM
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Ahh, didnt know that. Thanks for the heads up. Yea i will try that first. Hopefully i can get the bearings clean enough. Well if i dont im sure the motor will let me know before to long.
Again thanks for the info. Very helpful.
Dave
Old 06-07-2016, 05:42 PM
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Well if i dont take the sleeve out then i dont have to worry about takeing out those tight head bolts. Nice! Hopefully anything in there will come out the glow plug hole.
Old 06-07-2016, 07:34 PM
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As in the video, I would be extra careful and use a wooden ice cream stick to initiate sleeve removal, not anything metal like a copper plug gasket.
Other thing I would change from the video: don't hammer the front bearing!!! That kind of frightened me. I would heat the crankcase as in the video, get the rear and front bearings just started, then reinsert the drive shaft, prop driver, washer and nut and tighten down on the nut. The bearings will gradually get pressed into the crankcase. The improvement is that they are kept planar to each other, making sure you don't get one or both skewed, which would lead to damage. You always want all the advantages of keeping the bearings planar with each other and square to the crankcase. Good thread, nice to be cautious with nice ball bearing engines.
Old 06-07-2016, 08:32 PM
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Dave,

one book i ok I would highly recommend is Dave Gierke's book - 2-Strock Glow Engines for RC Aircraft. It is a great book that is highly educational for all things 2-stroke glow engines, including take down and rebuild. It's not necessary as I'm sure you will get good advice here, but I still think you will enjoy it.

Lars
Old 06-08-2016, 03:05 AM
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In this case, it is just cleaning out inhaled dirt. I would not pull the bearings unless they are worn right out. In fact I would not disassemble it any farther than needed. Just make sure there is no crunches when carefully turning it over. Maybe remove the liner, piston, and crank to get out the last bits of sand. I will put this in just as an idea. The combat guys drill them into the ground at 100 mph maybe every other flight, so they kind of know about cleaning dirt. Remember these guys run a bladder to flush the fuel out the venturi. I carry a Qtip in my toolbox in case of a noseover or, perish the thought, a crash. The last reply addresses this. http://aerohobby.ca/forum/index.php?topic=3.0

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Old 06-08-2016, 08:48 AM
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BrightGarden, John Brodbeck Jr. (from K&B) showed me the the trick of using a glow plug washer to remove a tight cylinder about 40 years ago. I figure if he approved the procedure it must be OK. Heat is one of the best tools for disassembling our engines, but it's not always available. I start with a Monokote heat gun. If that doesn't work I use a propane torch. My last line of defense is the kitchen oven. The proper tool to install bearings would be an arbor press, but not everyone has one. If you plan to replace the bearings driving them out with a hammer won't hurt, but it will only work for the front bearing. Severely rusted rear bearings can be removed with a 3 foot dowel. By now some of you reading this are certain I'm nuts. Custom fit a dowel to the crankcase hole where the cylinder goes. For example a 1" dowel can be fitted to a .40 case. Heat the case in the oven, insert the dowel being careful not to slide it in too far (you don't want it to over lap the bearing). Then rap the back of the crankcase on a board. I've never failed to get the most stubborn bearings out, and have never damaged a case. Of course you don't use the same amount of force that you would use for crushing rocks. Start out gently. Like I said before, there are many tricks to disassembling, and reassembling our engines. I should also add that there are many ways to skin a cat, and not everyone agrees on everything. I don't have a copy of Dave Gierke's book, but have no doubt that what he presents is absolutely first class. I've known Dave for over 30 years, and can attest to the fact that he is an incredible model builder, engine tuner, and educator.
Old 06-08-2016, 08:11 PM
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Wow , getting some real good advice here. I removed the carb , backplate and glow plug and washed the inside out with hot water , alcohol , blew it all out with air then sprayed wd-40 inside on the bearings. I used a small very stiff paint brush to wipe the gungy looking brown stuff off the bearings all around the inside of the motor as best i could. I thought maybe i had it until i stuck a q tip up under the piston and it came back a brown q tip. I dont see how i can get it clean without tearing it apart. I almost wanna just put it back together and hope for the best..
But i think the "best" probably would not be so good. I still have those frozen head bolts to contend with to . Im hoping some heat might help with that. If i cant get them out my decision will be made for me. I really appreciate all the help. I will let you know how it turns out........
Dave
Old 06-08-2016, 10:23 PM
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well i could only get 2 head bolts loose. I heated it up till i thought it was enough and a little more. Dam allan wrenches just strip right out. I have 3 allans that fit the bolts and i have been stripping them then grinding them square again and so on. The next step would probably be to cut slots in the bolts with my dremel and try a screwdriver to loosen them. But i think i would have to cut into the fins a little. Back to contemplating.
Old 06-09-2016, 02:52 AM
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Sorry you are having problems. Those head screws should not be so tight. You are only dealing with about 5 inch pounds. Make sure you use a good wrench and make sure it is metric. You might try soaking the screws in penetrating oil overnight. I used a heat gun to take my engine apart.

The rear bearing is an open face bearing. So if dirt was ingested, it may need to be cleaned. The front bearing is sealed so no problem there.
Old 06-09-2016, 03:11 PM
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is there such a thing as a good allan wrench? lol. I am using the right size also. The bolts just dont wanna come out. I did get 2 loose but that was it. So what i did was to give the motor another good wash down and catch all the rinse in a plastic tub. I could not see any dirt or anything in the rinse so i decided to call it done. I have already mounted it in a new plane. Haven't fired it yet but i think its gonna be ok. . I hope). I want to thank all you gentleman for your help. It was definitely a learning experience for me. This is a great forum. I probably will fire the motor in the next couple of days and i for sure will post so you guys can know how it turned out.... Again, Thanks
Dave
Old 06-10-2016, 04:23 PM
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As I recall, the head and back plate bolts are 2.5mm. Get a good, aluminum handle wrench. It'll set you back $6-$7 bucks, but it's a really good investment.

Another thing, again as I recall, the OS head gaskets for the .46 & .55AX are one time use. They crush down when installed and don't seal well on second use unless you get them EXACTLY in the same position. They are also pricey.
Old 06-13-2016, 11:06 AM
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Well I fired up the engine today. It hicuped a time or two but then ran great. I think it will be ok. I also discovered that it wasn't my transmitter that caused the crash, it was the receiver crystal. I have never had a crystal fail before but i understand its not that uncommon. Especially if the crystal has been in a crash. That one had been in several. Live and learn.. Thanks again you guys for the input. ....Dave

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