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champ YFM100 piston

  #1  
Old 12-16-2018, 07:46 AM
Weekend Warrior
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Default champ YFM100 piston

I bought a champ 100 for the grand kids. Thought it was a good deal,now I'm beginning to wonder. The top end was off the engine. Looking it over it appeared the carb choke plate screw came out went into the engine and bent a valve. Got all the parts to repair the head.. But I would like to have the cylinder bored. I cannot find a piston any where. Most sites sell rings standard and oversize but no pistons. Can anyone point me in the right direction.

​​​Thanks
 
  #2  
Old 12-17-2018, 03:49 AM
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Location: Lancaster England
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Looks like they are no longer available from Yamaha. Just checked Namura and they don't have them either. Try a few Yamaha dealers in case they have old stock, if that doesn't work, either try to get used components, or the old trick of finding a piston with about the correct dimensions from a different make and model of Motorcycle, Scooter etc, and get it machined to fit. Engine machine shops that do vintage stuff are used to doing this.
 
  #3  
Old 12-17-2018, 07:48 AM
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I just rebuilt one and got lucky being able to use the old piston. Look on ebay there was a shop that has the piston but I think they turn another piston down to spec. But they are $150 I think. You might have to look on ebay for a used jug that can just be cleaned to use your old piston. If you put the work into finding it you will get it running. I do have a bunch of parts left over from the 3 I had. Let me know if you need anything.
 
  #4  
Old 12-17-2018, 08:00 PM
Weekend Warrior
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Thanks,
i have the old piston. It's in ok shape just little beat up on top. The cylinder is ok. The cylinder to piston clearance is close to the high limit. But within range. Im going to put new rings in it and see what happens. While I look for a piston to fit it.
i may be contacting you about parts.

thanks again
​​​​​​​Tugg
 
  #5  
Old 12-26-2018, 09:05 AM
Weekend Warrior
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Join Date: Dec 2018
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Thanks,
Started putting it back together. Will see if it runs and let you know. I'll will keep the parts offer in mind.
 
  #6  
Old 12-26-2018, 02:52 PM
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New valves and valve seals. Over sized rings filed to fit original cylinder used the original piston. New timing chain and guides. New 30$ carb from amazon. It runs like a top.i did hone the cylinder also.
 
  #7  
Old 12-26-2018, 04:45 PM
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Good deal!
 
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