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  1. #1

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    FS-120III Disassembly

    I am in the process of replacing my main bearings on this engine and came across several issues in the process of disassembling the motor. I have removed everything so that I'm down to getting the rod off of the piston, sliding the piston out, removing the rod from the crank and pushing the crank out the back of the engine. Is that sequence correct?

    1) I am having trouble getting the wrist pin item #13 (P/N 45506010) on the parts list out of the rod/piston assembly. I understand it comes out the hole in the rear of the cylinder casting but am unable to coax it out. When I look on the exploded view in the manual I see a piston pin retainer item #14 that appears to be a spring clip on the end of the pin facing the front of the engine. Is this preventing me from removing the pin? Please advise best way to remove the wrist pin.

    2) During the process of trying to remove the wrist pin I slid the cylinder liner up to expose the wrist pin to the hole in the rear of the housing; inadvertently the liner slipped past the piston ring. When I finally get the piston out of the cylinder I was planning on compressing it and sliding it back into the liner. Is there any problems with that fix?

    3) I will be replacing the cam cover due to damage removing it, and was going to replace the bearing in it which I assume is accomplished by heating the cam cover then sliding a room temp cam bearing into it is that correct?

    4) I heated the motor to break loose the cylinder liner when I did that the cam bearing that is opposite the cover was in the casting, will the heat affect it? If I wanted to replace it how would I?

    5) When I removed the cam from its housing I didn't notice its orientation. I'm not referring to timing which I believe has the lobe closest to the cam cover pointing up along the push rods at TDC. What I mean is which end goes into the housing first, one end has an oil hole in the center-line of the cam does it face towards or away from the cam cover?

    Any help on these issues is appreciated, and any reference to detailed instructions for bearing replacement would be appreciated.

    Thank you

  2. #2
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    RE: FS-120III Disassembly

    To help you out:

    1) We use a sheet-metal screw or screw extractor inserted into the hollow wrist pin to pull it out.

    2) Once the piston's removed from the engine, you can put it back into the liner, sure. Won't hurt a thing.

    3) That's correct...heat the cover, tap out the bearing, and then put a cool bearing into the hot cover.

    4) Heat won't affect the bearing. To remove that one, heat the case and rap the case against a wood block to knock out the bearing.

    5) There's a dot on the side of the cam gear. That dot faces out. Here's the proper orientation of the camshaft:
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    Bill Baxter, Manager Hobby Services/Futaba Service/North America
    3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
    Service Phone: 217 398-0007
    Email: hobbyservices@hobbico.com

  3. #3

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    RE: FS-120III Disassembly

    Bill,
    Thank you for the information. Several more questions to clarify.

    1) Do I have to remove the piston pin retainer prior to extracting the wrist pin or does it come out attached to the wrist pin?

    2) Are the wrist pin and piston pin retainer reusable or do I need to buy new ones?

    Thank you,
    Lawrence

  4. #4
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    RE: FS-120III Disassembly

    The piston pin retainer doesn't need to be removed. It is only on one end of the piston pin. All parts can be reused if they're not damaged.
    Bill Baxter, Manager Hobby Services/Futaba Service/North America
    3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
    Service Phone: 217 398-0007
    Email: hobbyservices@hobbico.com

  5. #5

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    RE: FS-120III Disassembly

    Well I put the engine back together, and I don't have any compression. I set the cam timing with the dot aligned with the push-rod tubes at top dead center. I adjusted the valves per the manual and while turning the prop around there is no resistance at any point in the stroke. I noticed when I took the motor apart there where two stacked head gaskets one silver and a second copper colored so I put them both back not sure what the order should be though.

    Please give me some troubleshooting hints to find the problem.

    Thank you,
    Lawrence


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