Missing my top piston ring retaining pin!

Discussion in 'Motorized Bicycle General Discussion' started by Cannonfish, Feb 28, 2010.

  1. Cannonfish

    Cannonfish New Member

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    So I took off my head and cylinder this afternoon for an unrelated reason (winter boredom), and I noticed that my top piston ring can spin freely around the piston. The little pin that ordinarily keeps the ring in place is missing!

    I haven't noticed any problems up until now, and the sides of my cylinder aren't scratched up. I wasn't particularly violent when I took the cylinder off the piston, so I don't think that I dislodged it in the process of opening the engine.

    So my questions are, is there any chance that my engine has been running this far (~250 miles) without a pin to retain its top piston ring? Do you guys think I can just put everything back the way it was and be okay?

    I've looked around, and I can't find any vendor that sells piston ring retaining pins... What should I do?
     
  2. oldspeedsi

    oldspeedsi New Member

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    never herd of that rings are supposed to be free i pulled one apart and just to fat ass rings nothing complicated like that.
     
  3. tommyboy1442

    tommyboy1442 Member

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    every engine i ever built never had pins holding the rings in one place. i believe those rings are supposed to be able to slide around the piston. i usually just set the ends of the two rings apart from each other and call it a day and install it, never had a problem. i havent pulled the piston on the chinee yet, but i dont know of any pin holding the rings from spinning. hey, wheres norm at......or anyone thats done a teardown, anybody?
     
  4. wildemere

    wildemere New Member

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    Its a two stroke thing.

    If a ring end gets into a port opening it can snag on it and snap.

    This causes major damage and a possible lock up.

    The answer to your questions are;

    Probably

    and

    I doubt it

    For saftey and engine life you must have the pins.
     
  5. professor

    professor New Member

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    Look for a pin hole in the piston. Maybe there never was one.
     
  6. Tcams

    Tcams New Member

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    I took my head and cylinder off to paint and the rings on my piston are spinning freely. Did I lose a pin as well? I definitely dont want my engine to lock up.
     
  7. BarelyAWake

    BarelyAWake New Member

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    wildemere's on the money;

    [​IMG]
     
  8. oldspeedsi

    oldspeedsi New Member

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    yep my spare 50cc RAW has em I just tore one down for the first time to clean it up (found metal shavings in ports eek maybe its a good idea to clean these things up before first run? but yes i now think that they are definitely there for a reason. (ports are in the cylinder) just my 2 cents.
     
  9. diceman2004

    diceman2004 New Member

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    yes , 2 strokes have ring pins ( for reasons previously mentioned ) and the damage they cause if they pop out is quite severe ( usually a ring has to get snagged on a port to loose a pin in an assembled engine ) but then you would have a broken ring and a damaged cylinder .

    you guys didn,t loose the pins , they were never installed in the first place
     
  10. Tcams

    Tcams New Member

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    Took my head and cylinder off again and I found em'. Thanks for the pic barely
     
  11. corgi1

    corgi1 New Member

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    where were they:confused:
     
  12. Tcams

    Tcams New Member

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    They never moved, its just when I put my cylinder back on i didnt know the rings had to be in a certain place. So I took the jug back off and found out that the rings where in their correct placement. Thank god
     
  13. 2door

    2door Moderator
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    I just today disassembled a warranty return engine from one of our sponsors. The customer said the engine was seized and would not turn. This was a new 2 stroke engine that had never been run. I found the top ring gap was not aligned with the retaining pin but had been jambed into the cylinder. If the ring gaps are not aligned with the pins you have a 'high spot' in the ring that can damage the cylinder walls and piston. Thankfully the customer did not try to force the engine to turn but simply returned it for a new one. This one was lucky and will live to run again.
    Tom
     
  14. diceman2004

    diceman2004 New Member

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    oops CANNONFISH i forgot ( any marine engine repair shop will have those pins )
     
  15. bairdco

    bairdco a guy who makes cool bikes

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    the rings will spin freely around the piston when it's not compressed by the cylinder wall. so it might actually be there, it's just not lined up right.

    and you DO have to line them up, otherwise, well, read the other posts in this thread and you'll see.
     

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