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Old 46AX Worth Fixing?

Old 04-20-2020, 03:18 PM
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Unhappy Old 46AX Worth Fixing?

Bearings in one of my 46AX's are gone. You can hear them when you rotate the crankshaft. I've replaced bearings before but question whether it is worth the effort as the engine has minimal compression. It runs fine at WOT but will not idle below 3,000 rpm. I used to start it by flipping the spinner against compression but now need to use a starter. I guess the real question is how do you decide that the engine is too worn? I don't think there is any way to rebuild this type of engine.

Murray
Old 04-20-2020, 03:38 PM
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J330
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OS parts are too costly in my opinion when it comes to liner and piston, it's out of the question if you got more going on than that. You can get a used clean AX46 for $55. https://www.rcgroups.com/forums/show...ngines-all-run

With the virus issue hitting the economy, even a new in box AX46 on feebay might be good timing for you. Certainly less than LHS.

​​​​​​https://www.ebay.com/itm/OS-46-46-AX...59.m1431.l2649

Last edited by J330; 04-20-2020 at 03:44 PM.
Old 04-20-2020, 08:41 PM
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bigtim
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if its just the Bearings its a super easy swap out, with this C-19 thing going on I am on a rebuild kick been working on my project engines getting them ready for when we can fly,1 OS 4 stroke down 2 more to go.

2 stroke bearings are even easier because there is only 2, you might need a gasket kit for your AX I have the same engine in a little stunt plane its a great little engine, I would check youtube for bearing removal tips, some basic tools are needed but nothing too crazy, because of my having multiple engines I invested in a sonic cleaner since I knew I was going to do multiple engines and I had other projects but cleaning your engine parts can be done with a little glow fuel in a pinch, I purchased after market bearings for very little, less than 20 bucks.

the key is pay attention to how you break down the motor, get some information on pulling and and installing the new parts and don't be in too much of a hurry and you will be good to go, my tear down and cleaning of a 4 stroke took me about 4 hours I was so intimidated, I had that one reassembled, oiled, and ready to go in a couple of hours, and was on to number 2 which was a bit rusty when I got into it and it still only took a couple of hours.
Old 04-21-2020, 02:11 PM
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J330
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Boca bearings sells bearings reasonably cheap and are great quality, and many rebuild posts on youtube, like this guy used to do, before his cat died....

Note the reputation of the nickel liner in the FX? Hopefully AX is better. Steps are about the same between these two engines. Pull your engine apart, inspect first, before you buy anything.

Last edited by J330; 04-21-2020 at 02:13 PM.
Old 04-21-2020, 03:45 PM
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Thanks all. I've replaced way too many bearings for it not to be a slam dunk. The 46ax's came from new with crappy bearings so I have the technique down. Also have a couple of spare sets!
Was checking the bearing noise a bit ago and found that the compression was better than I thought so will set up and check it tomorrow. Agree that OS parts are way too expensive. Had a weird crash a couple of years ago that broke one mounting flange off a 120AX. Rest of the engine is fine, bearings included. Didn't even break the spinner. They want $125 for the crankcase. A complete new engine is $250.

Thanks for the video and reminder of the nickel plating issue. The 46ax's do not have that problem. I found a NIB 46sf at the bottom of my "engine" collection box. Did they have the nickel plating issue? If not, might pt it in one of the planes I will build on of these days.

Murray
Old 04-22-2020, 07:17 PM
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I have several FSR, SF, FX, AX engines and have flown them all through the years, but not enough to wear any piston/liner out especially only using them for sport plane flying, not racing or pylon type planes. I usually buy used, so I rarely know the true number of seasons on them when I start flying them. The only failure on the SF series was with a .61 and I bought it that way. I've seen a .46 SF once posted on RCU years back with a wiped out liner as well but nothing stated about how it got that way, could have been abuse. I personally never lost one. I had an OS RF 61 for a few years on an Ultra Sport 60 and it did very well. What is cool to note is FSR and SF series engines is that they came in both ABN and ringed versions.
Old 04-22-2020, 07:26 PM
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the Wasp
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I say don"t rebuild it. it will cost to much.
I say buy a clean, used Saito 56.
I say if you must have a 2st buy a use OS 50sx.

Jim
Old 04-22-2020, 09:51 PM
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bigtim
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Dave McIntire is the man when it comes to rebuilding engines I have learned so much from his videos, thankfully they still live on youtube for a reference, after years of building engines he decided he was over it that was me about 5 years ago, now I am working on my shop and getting back into the hobby again I have so many projects all I need is bearings lol.
stay healthy and have fun BT
Old 04-23-2020, 02:21 PM
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Originally Posted by the Wasp View Post
I say don"t rebuild it. it will cost to much.
I say buy a clean, used Saito 56.
I say if you must have a 2st buy a use OS 50sx.

Jim
Thanks, Jim. Got a chuckle from your post. Much as I love the Saito's (have a 100 in a WM chipmunk), I'd find it hard to justify buying another engine. Besides the two 46AX's in the two T-34's, I have two others with new bearings and one NIB. In that size range, I have a Tower 46, the OS 46SF, two Irvine 56's, a YS63 and a few more in the bottom of the box. Oops, almost forgot I have a couple of planes hanging from the ceiling but can't recall what's in them. (Yes, they were put away with MM oil after being run dry.) Think I'll take a hint from Jonnybgood3 and advertise some engines.

Went motorcycle riding the last couple of days so have not checked out that engine yet. I have new bearings for the engine so if that's the only problem, I'm good. If the compression is shot, the engine is scrap. Not paying $90 for a new piston and sleeve.

Murray

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