The best penetrating oil of all is "oil of wintergreen". I can smell traces of it in MMO. OOWG is very expensive, used by deck hands on battleships to change out gun barrels. It works along with heat. A little goes a long way.
PB rust blaster is very good.......WD40 not as good, it seems to be more of a rust attractor.
A 50-50 mix of acetone and ATF is reported to work very well.
Hoppes gun cleaning solvent is very good, too.

OK, I got it!! No laughing though but it's almost all back together again. It is an OS .91FS so no, I couldn't cut slots. Don, some of my older ellen wrenches are really short!!! I never buy new ones, I have a tool box full of them.
I just kept sticking the engine in boiling water then pulle it out and used a punch with a big hammer and gave the screws a heavy rap then stuck the engine in the freezer. I did that several times then all of a sudden they came out.
Now for the bearings!! The front one came right out with a little help from a wooden dowel and a hammer, the rear one was really stuck and not even going to pop. Back to the boiling water and some whacking, no way. Boiled it for a very long time, pulled out a round flat bottem punch and really gave it a smack. My, how easy they slip out with the correct tool.
The bearings were packed with nasty old Castor and pretty scored, you could hear the grinding when I flew the plane. I have pulled out bearings that were a lot worse then these, at least these wree still in the races.
Had the engine about half together when I discovered I had forgot to install the lifters!! No the head screws wouldn't come out again?? I took an old easy out and ground it down to fit then they came right out. I went ahead and replaced the head screws at that point.
Engine is almost all back together but I got tired of fooling with it last night, .
I think it was Aeros idea about heating and using the freezer, that seemed to do the trick.
Don, the wrench I was using was getting a little short from grinding so I went into my box and found a nice new one and did your tap in with a hammer trick, it seated it very well and held on so I could get them to unscrew. Why I didn't replace them all before I tried to reassemble?? Sometimes I just do some stupid things to try to save a buck.
Thanks to all of the guys for the input, trust me, I tried them all. That set of screw removers sold at Sears worked pretty well from what I have been told but you have to buy the complete set and I seem to have ran out of money so I'm working on the cheap right now. I had a set like that years ago but they got up and walked out of my tool box??
Thanks guys, everyone was a big help and maybe some of the new guys learned something. Even old hands at engine building get there mules kicked once in a while. This one fought me but I won the battel in the end!!
Gene

I am glad you won the battle.

If you heat the case with either a propane torch or in a toaster oven the bearings will fall out, they wont need to be "whacked" or forced. Same goes for reinstalling the new ones.

Good job Gray Beard!

Now I know where to send my engines in need of bolt and bearing removal-Thanks Gene!

Mark, thanks but no thanks!! I used to rebuild for other people but if I would have gotten one like this it would have been the last one done for a friend.
This engine was given to me a couple of years ago as a gift. Just a great running engine and fits my old Kaos perfectly.
I also looked at the price listed in tower for a new one, $300 magic beans so I wasn't going to let it beat me. No one even mentioned anything about me forgetting to install the lifters!!
For any of the new guys I posted up a photo of a home made air cleaner on this engine. Sorry wife but you can live without wearing two nylons!!
It's just the thick end of nylon hose over the carb held on with a very tight O-ring. I fly off of a dry lake bed and this helps keep the grit out.
Anything that helps keep me from rebuilding it again is OK with me!!
Price of the rebuild was about $13.00 but I just happened to have a new ring in my supply box. So for about $25.00 I have a new engine and saved myself about $275.00. Worth the effort!!
Gene

That's great! Good job, and good looking OS 91FS.

Gene, great news. It gets to the point thay you refuse to let that little pile of screws and almuminum get you down doesn't it.

Why is it you see things like the lifters after you get things back together? I pulled the same thing today. My Mag 70 was running rich on the low end and when I went to turn the mix, there was zero drag on it. I wen't ahead and had a couple good flights and when I got it home, I pulled the engine and then the carb and with that carb, you have to pull the barrel to get the mix needle out, it screws all the way in. I get it out and paw through my engine parts, find a new O Ring and put every thing back together. I just tightening the last nut on the weight bar and noticed the spring that goes between the carb body and the barrel. GIRRRRRrr. every thing comes of and apart again then I can put the spring back in place. You know when you take things apart and put them back together again enough times, you can do it really a lot faster than the first time.

Don

I have an old aluminum baking pot that I use when working on an engine. I clean the parts in it with alcohol and a wire brush and tooth brush then just leave everything in there and use a rag to wipe them off before they get used and lay them out on a white towel. I also have two computer chairs and both of them leak so you start out looking high over my bench and end up looking at the bench side. On this build I had every tool I owned on the bench so it was really cluttered so I had no room to lay out the parts. I saw those tappets in the pot and told myself several times not to forget them. Maybe it's an age thing?? That old mind like a steel trap line I used to use seems to be lost with the ages!!
Magnum!! Anyone have a carb for a .91 Magnum they don't want?? Too long of a story but I could really use one.

You ain't going to get off that easy, Tell us the story. Do you need the carb body, or parts to it?

Don

Good job on the 91 gene-Totally worth it. Probably the only engine i would buy at a swap meet (price being right of coarse). They just run perfect. I did a build on a 4*60 i think you read it, the 91 in that thing has been outstanding from day one and 80+ flights later. Bought another one before Tower or OS jumped the price. I think it came to 215 or 220. Feels like a great deal now. Good luck with it.

Thanks Mark, it is a good running engine even with the bearings growling it out performed the Saito 100 for some reason?? Should run a lot better now without the bearings fighting it.
Short story on the Magnum is it was a 4th or 5th hand me down that belonged to one of my students in a 60 no name trainer. It has always run but never run very well, even under powered for a Magnum. Another student bought the plane complete. The carb low end needle is out 9 turns, always has been and it can not be adjusted, one little touch from what we will call the sweet spot and it dies. My friend rebuilt the engine completely, I went through the carb and installed all new O-rings, the carb has been gone through several times by now and nothing seems to be of any help. I can tune it to keep it running and fly the plane but it isn't right or correct, one click either way on the high end results in a dead stick. I had it running pretty well here in Vegas but the owner took it to Utah and it wouldn't run at all there. I talked him through the tune on the phone and he managed to get in a few flights so it's running again. You also have to tune it backwards, low end first then the high end, very gently a little at a time through the mid range until it will transition.
I have parts all over the shop but nothing for a Magnum but I would like to try another carb. I plan on using this plane and engine this winter for training but would hate to put a student on the box the way this one runs. I have no idea about the history of this engine, what another owner has done or if the engine was crashed in some odd ball way but I'm sure a new carb would be the answer.
That's the short story, there is more but you get the idea. I have a bunch of engines under the bench but nothing but a couple of MDS engines in 60s so I want to stay with this Magnum.
Gene

Your on the right track, I would say it needs a new carb, maybe a casting flaw or the internals of the needles are flawed. Iv'e never tryed this but would the OS 91 carb mount up just to see if it runs good?? I don't have a 91 Mag. or I would try it.
Good story though

Gene, it will take you about 2 minutes to decide if it is the carb or not. Put the carb from your O.S 91 you just rebuilt on it and see how it goes. They fit like a glove.

That needle seems strange, I woud set the mix needle so hte screw slot is flush with the end of the trotle arm, the factory start point, and then adjust up the top end. I went nuts on my Mag 70 trying to adjust it. It was behaving like you describe. The more I tried, the worse it got and when it got to the point that it was about to shake the engine off the plane on the bench, I finally decided to read the manual and set things up as they suggested. WOW what a difference. There just isn't much to go wrong in that carb. Make sure you can blow fuel through the spray bar, nothing stuck in the grove, and after that, it's straight forward. My trouble was that I was trying to screw in the needle to a stop to find my start point, and on the 70 and I think the 91, the idle mix scrws out to a stop. Then you turn it in about 2 1/2 turns if memory is correct.

The magnum high speed needle is used on almost all carbs, and all show the same PN for replacement. However, not all needles are the same. The Mag 52 came with a stubby ramp and a rather blunt nose, I pulled the high speed out of a Mag 61 two stroke and there was a noticable difference in the taper and tip size. Swapping the two let me tune the 52 a lot easier. You may want to check that.

One other issue with the Magnum Carbs is that they over machined the groves in some mix needles and the Oring didnt fit snug and would loosen up after a half gallon or so. I watched the one on the 52 slowly turning while the plane was on the bench. On that one, a new O-ring only fixed things for a day and then it was back to the old habits. A new idle needle fixed the problem.

Last check the valve timing. The manual is not very clear, but it times just like the O.S., the dot is along the line of the pushrods not 90 degrees to the crank.

Don

After what I just went through and just got my engine back into the plane and cowl back on I need to take it apart to get at my carb?? Oh Lord!!! No, I didn't know the OS .91 carb was a fit on the Magnum, I can tell you the OS 1.20 carb doesn't fit!! I had an extra and gave it a trial fit, no go.
I will print this out and start over as soon as the plane comes back to town, sometime next month.
Right after the rebuild I did set the carb back to factory with no luck. Looks stupid with the idle jet sticking way out too. No one should fly a plane with a stupid looking engine in it!!!

That is the best penetrating oil ever.

Best I have ever used and I have a turned a few wrenches in my life.

Can I break down what can be done as in a "Cliffs Notes" version of how to remove stubborn threaded fasteners of dissimular materials? Please, thank you, I will anyway! lol

Steel bolts threaded into aluminum is a disaster to begin with unless the bolts are coated with something like never sieze. Somebody mentioned electrolysis. That can also be something else like galvanic reaction which is pretty much the same thing. What happens is the steel bolts going into the aluminum will actually weld themselves together on a molecular level when you add in extreem temperature cycles over time.

How to remove those stubborn bolts.

You have to break down that molecular bond. Start with something like PB Blaster overnight and the shock method I mentioned earlier by tapping with a light hammer. You have to use a "LIGHT" hammer. It has to be a sharp tap, not a heavy blow. Use a good quality wrench and if it's a allen head, use a precision ground tipped one like the car guys use.

If that still doesn't work, run temperature cycles. Throw it in the oven at about 250*F for an hour, then toss it in the freezer for awhile if you dont have environmental chambers and an engineering lab like I do!

Wash, rinse, repeat! Works every time!

Edit: Im running some tests at work on some 6-32 screws torqued to 6 foot pounds with, and without nylon patch. The tests will be ran over several days at -40*F to 140*F. I doubt the nylon patch can handle the high heat extreems of RC engines, but I can test something else if anyone is interested.

Gene, a quote from me at age 10, "MOM, how come I have to learn everything the hard way" I don't remember the answer. I've found over my life that the hard way lesons seem to stick though.

About a year and a half back, I broke a O.S52 down to scrap metal and I salvaged the carb parts. I've got three Mag 52's, two have never been out ot the box, got them in the 1/2 off salethis spring from Hobby People, andthen my old troublesom Mag 52 that was on my trainer. It gave me fits and Hobby People sent me a new carb that worked great for about two tanks. I sent the engine to them and theydid a go over and it ran about the same when I got it back.Most all of my problemswere with the low end,if you cut the throttle full, it would quickly drop to about 3500 and then slowly dropdown to around 2500 and die. Icame across theO.S. 52 on ebay and bought it. Same bolt pattern on the mounts, and Ionly had to find a way to accomidate the carb as it wasquite different fromthe Mag 52. On a lark, Ichecked to see if I couldswap them andfound that they have the same bolt pattern where the attach to the back plate, and the fit to the manifold was exactly the same. Isince found out from W8ye that most of the exterior parts are interchangable, and some of the internal ones, on a like engine swap.When I crunched the O.S. 52, I made sure to keep parts although anything aluminum was broken or bent. I've got a second O.S. 52 in a little Fun Star and when I get around to the P-61, I'll pull it's carb and put it and the one I built up from parts from the crunched engine on the two Mag 52's I bought for that plane. For what is's worth, the old O.S. 52 carb and the Mag 52 carb will fit the new O.S. 56A engine. I picked up a vecolity stack for that engines carb and have it on my O.S. 52 in the fun Star. It sure keeps the firewall clean.

Let me know how it goes. Iknow what you mean about taking off the cowl and engine. That suoukoi SU -31 I bought has had the cowl/engine off at least 20 times since I got it a few weeks back. Isay Cowl/Engine as both have to come off and go on at the same time. And, I put 24 screws holding down the cowl. Man, do they hold. The last time out with it, Idead sticked on take off and nosed in, crunching the cowl and ripping out the landing gear mount. The attacment line of the cowl didn't move, nor were any of the screws jamed, even though most of them were into 1/16 balsa with some CAhinge pieces CAed to the back.

Don

Don, I often ask myself why I keep doing these things?? Then it hits me, I'm cheap!!! I never had the money to do things so I ended up learning to horse trade and do things myself. I'm still having fun with it and enjoy myself so I must be doing something right. My friend that bought that trainer has been fighting that Mag right along with me and he isn't going to give up either. We just talked about it the other day over the phone, he was at the field and I was able to walk him through the way I got it running and he was able to get it good enough to fly the plane. I will email you when he comes back with it and we start doing out probe into the why's of it all.
Gene

I'm new to R/C, but I spent a lot of time as a boat mechanic. When steel bolts get stuck in an aluminum block, the best way I've found to get them out was to treat them to a liberal dose of Liquid Wrench or similar, wait a while, then try to get the bolt to tighten just a little before loosening. This will work most of the time. You can try whacking with a hammer while the oil is seeping in, to help it coat as far down as possible. The dissimilar metals sometime react together like they are welded. Hope this helps. Jim