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This motor had 30 + hours on it, almost every one pinned 2nd and 3rd on kart tracks. I had a FMF 4.1, lightened flywheel, CF primary gear, TB manual clutch, TB cam, VM26, BBR CDI and a Kitaco Super Coil. When it blew it was running VP C12 fuel (and stock piston), so I don't think it detonated it self to death. Looks like it dropped the EX valve and the destruction started.

It happened on a downshift under braking from 3rd pinned to 2nd, business as usual. I had noticed the last 2 times at the track it was trailing a little smoke on decel, but normal on accel. I had planned a rebuild after last Saturdays practice anyway.

Metal is everywhere, in the pipe, the carb, the cases........

The hole in the piston is curiously dead center to me, but this is my first blown mini engine.

Feel free to chime in, enjoy :)








 

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hahahahahaha, nice man... been there done that... but rebuilds are the best part

heres what happened to my head when i leaned out running 28psi
 

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The only reason the hole is in the center of the piston is thats were the piston is thinest. Everywhere else that piston has lots of metal behind it.

I sure hope your hitting the brakes hard before you down shift. You do know that a rev limiter does nothing during down shifts and thats the easiest why to blow up a engine.

The engine is not a brake and should not be used as one. Unless you have a factory repair man rebuilding your engine between each round.
 

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thanks to trail bikes it will be cheap to rebuild, stock 110 pistons and cylinders are everywhere and cheap. How did the combo run? it should cost about half what a 150r HEAD would be to rebuild.
 

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:eek: Holy crap bro !!!


I don't like to see this kind of stuff posted when I'm about to finallly put my 110 motor together for this weekend races . :headshake


Sounds like you motor was try'n to warn you that something bad was gonna happen soon , eh ?


There are many diff things that could cause this problem .

- Are you run'n stock valve springs ?

- What brand , weight and type of oil are you run'n ?

- Do you let the bike come up to temp before hammer'n on it ?

- How often do you change out the oil and filter ?
 

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when was the last time you checked your valves?
Haha... looks like he just did!

Just kiddin.

Hey Filthy. I have two spare heads and one 59mm cyl in the garage if you need. One is a stock head ported by AHP and the other is a 2bros big valve head. Also ported.
Both heads are low hour and should be fine for a good while.

I have a k10 cam too if you need that. Just let me know. We can work something out.
 

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Discussion Starter #10
Haha... looks like he just did!

Just kiddin.

Hey Filthy. I have two spare heads and one 59mm cyl in the garage if you need. One is a stock head ported by AHP and the other is a 2bros big valve head. Also ported.
Both heads are low hour and should be fine for a good while.

I have a k10 cam too if you need that. Just let me know. We can work something out.
Thanks, I have a stock take off head ported by Cat 5, and take off stock cylinder bored .5mm over for a Weisco 11:1 piston. Got a new Tak K10 ready to go also.

Should be back up soon, and faster!
 

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Holy Cow:eek: Now that's how you explode a motor. Looks like you floated the valve. Could have been from the motor over revving(usually) or maybe just weakened valve springs. Perhaps stiffer springs and retainers w/ some stainless valves are in order this time. Lol Good luck with the rebuild. You might try CHP if you can't source any parts you need here.
 

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ummm....... who are you talking too? and which post are you referring too? If you're referring to my rare head comment it was in reference to cobongo's post(see quote and original pic) in which the head pictured is a PR8 head which is an oversized B20b head from Japan(not avail in the U.S.A.)
 

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that definatley looks like loose valves/ weak springs. and some floating.... that sucks! I havent seen a 110 grenade that bad yet. oh well, its just man made.
 
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