BRAND NEW YD100

Greg58

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May 1, 2011
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You'll hear a lot of opinions on the engine and the frame, I have had good luck with my aluminum frame and 48cc engines. My first bike which I still have is almost 9 years old with no frame problems. Cannonball rides along the coast where it gets very hot, he hasn't posted anything about his giving problems.
 
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MTBNewf

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Jan 19, 2020
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You'll hear a lot of opinions on the engine and the frame, I have had good luck with my aluminum frame and 48cc engines. My first bike which I still have is almost 9 years old with no frame problems. Cannonball rides along the coast where it gets very hot, he hasn't posted anything about his giving problems.
Yeah.

I understand the rational but bein an old mtber, something inside me screams "NO STEEL FRAME". lol.
 
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Greg58

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The 40mm ad 47mm pistons have pins in the ring grooves to keep the rings in place, the pins are located on each side of the intake port.
 

Greg58

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Look at the ends of each ring if they are designed for locator pins they will have a half Moon cut on the bottom half. If the ends are flat they aren't.
 

FOG

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Mar 3, 2019
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That's too scary too contemplate.

Years ago. Holed a piston in a Zundapp. Couldn't find no Zundapp piston but a Yamaha had the same dimensions. Except for the locating pins. It fired up for about half a second when a ring snagged a port and chunked the cylinder.

End of Zundapp.
 
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MTBNewf

New Member
Jan 19, 2020
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That's too scary too contemplate.

Years ago. Holed a piston in a Zundapp. Couldn't find no Zundapp piston but a Yamaha had the same dimensions. Except for the locating pins. It fired up for about half a second when a ring snagged a port and chunked the cylinder.

End of Zundapp.
there are spossed to be pins in 2 stoke pistons, yes?

So what now?
new piston? modify this one?
 

Greg58

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Looks like the ring ends do have a taper so spin the rings all the way around and look for the pin. There’s no way for the engine to last if the ends are not stationary.
 
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MTBNewf

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So, I got the flash cleaned up, transfers smoothed and matched a bit, matched up and textured the intake track/polished the exhaust port and got the gaskets trimmed up.

Gonna figger the mounts next.
once she's on the frame to my satisfaction, won't be long for first run.
 
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MTBNewf

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SO.....gonna hold off on firing her up for the first time.

Just read some stuff on break in and there are some of the opinion that you should put the motor under a load as soon as you start it up, (to seat the rings), the first time.

Thoughts?
 

Greg58

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I like to put the engine through a couple of short heat cycles at first, the road I live on is half a mile long so I make two to three runs up and down varying engine speed. I then let it cool and repeat, I've had good luck doing this. After that I don't make super long runs but I do increase ride time. After 4 to 5 trips if the engine temperature seems good I'll ride it as much as I want.
 
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MTBNewf

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Jan 19, 2020
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SO......She runs.

Started up first try.
CNS carb seems fine atm.
haven't burned the first gallon of gas yet but she seems to pull fine.
I've been every where on her for short runs. some good hills.
usin mid grade gas and Castrol 2T Go @ 24:1

really diggin not pedallin up hill.
Thanx for all the help

Cheers
Jim
 
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