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change bearings in OSFX91

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change bearings in OSFX91

Old 01-09-2012, 04:42 PM
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Default change bearings in OSFX91

I am haveing a problem getting the rod off the crank pin in order to change the bearings in this engine. I have the liner out and still can't pull it off. What am I not seeing? Help please,
Old 01-09-2012, 04:58 PM
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Default RE: change bearings in OSFX91

Have you tried heat? Id say put it in the oven at 350F for about 20 mins then try when its hot.
Old 01-09-2012, 05:01 PM
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Default RE: change bearings in OSFX91

Its not to tight on the crank its just not enough clearance between the rod and the rear of the crank case to get it off.
Old 01-09-2012, 10:07 PM
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Default RE: change bearings in OSFX91

I haven't worked on that engine before, but it's always worked for me to go to TDC and use a pair of needle nose pliers to remove the rod.
Old 01-10-2012, 05:19 AM
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Default RE: change bearings in OSFX91

could the crankshaft have slipped out a bit? maybe trying putting a prop on and tightening it to make sure it is pulled all the way in. I've rebuilt my 91fx a couple times and had no problem with room to get the rod off.
Old 01-10-2012, 07:38 AM
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Default RE: change bearings in OSFX91

I tapped the crankshaft down tight with a wooden dowel, it was already down then got a stiff piece of wire with a bend on the end and was able to pull the rod off the pin. I have replaced bearings in a lot of motors and never had this problem befor. Now the trick will be to get it back on the pin after changing the bearings. Thanks for your in put
Old 01-10-2012, 09:20 AM
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Default RE: change bearings in OSFX91

The rod slides back and forth on the wrist pin. Sometimes that pin gets a build up of gunk on it and the rod wont slip far enough sideways to clear the crank pin. Clean it up and use a little light machine oil when you put it together.

Seen that several times when rebuilding heli engines.
Old 01-10-2012, 09:45 AM
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Default RE: change bearings in OSFX91

Well I had no problem putting the rod back on. Now I feel play in bottom bushing on rod. Will try it next week end a see how it does. While the bearings were stained kinda red (I think from the fuel) they felt good turning them in my hand but may not at higher speed. Thanks for your suggestions. Floyd
Old 01-10-2012, 10:20 AM
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Default RE: change bearings in OSFX91

In out play or play around the bushing? If its in out its no big deal, if its play between the bushing and the crank pin you're going to have problems. I have pic's of a heli engine that blew that bottom end of the rod out from play between the bin and bushing

If you clean and dry the bearings, and put some side pressure and they feel clean, then the bearing is good.
Old 01-10-2012, 04:23 PM
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Default RE: change bearings in OSFX91

I can see movement up and down and feel a bump when turning it. It is my sons engine and he wants to try it this week end to see how bad it is. Time will tell, probably very short time! Thanks, Floyd
Old 01-17-2012, 04:17 PM
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Default RE: change bearings in OSFX91

Well into the first flight engine quit running. I could hear rod tapping. Pulled it off and can see bronze from bottom bushing slung around inside of the crankcase and now lots of up and down play between pin and rod. Have to decide now wheather its worth repairing.
Old 01-18-2012, 07:05 AM
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Default RE: change bearings in OSFX91

I'm shocked

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