Snapped Crank!

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lol ive snapped the crank on one of my lifane 146cc looked the same as that only snaped because of over revin it was a 1 down 3 up had the nuetral probs so we just kept it in 3rd and fed it until she blue then i got an all up 146cc and know i got the 150cc and put the 146cc in my china crf50 its so funny lol it wheel stands every gear u got to be a nut to ride it.
 
topguntravis said:
where did u get the engine from?
i'm ganna rebuild my engine before warranty goes on my bike now so i can get free parts if they are stuffed up.
how did u notice that it had happened? when u were riding?
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was riding and lost all spark...due to the flywheel giving the cdi instructions on when to spark

so after swapping coils and all sorts of stuff i opened up the side cover to find the flywheel falling out with a third of the crank with it

bike had never been over reved...was only new

they have limiter to stop that anyway..
 
cass38a said:
My lawn mower snapped the crankshaft and chucked the whole boss and blade assemby out the bottom just this morning. I should post up a picture of the crank for Cactus to keep him busy. BTW a new briggs and stratton Quattro engine is worth $240, will take a week to arrive, my lawn is only half mown (looks crap) and we have had so much rain this week that the new engine will cop a hiding on it first hit out.
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Ha Ha Ha ... Yeah the good ol' Briggs and Strattons can be a good motor ...
They are raced over in the US and here and there's a lot more to building race winning performance engines than most people think ..

Seal Your Engine for Winning Performance  by Joe Mondello Feb 2001
 
themountain said:
no they don´t:p
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Right on mountain .... ;)

It's well known to engine builders and racers that revving a new unseasoned engine too hard from new can cause it to fail early ... A lifan 140 has a 59 mm stroked crank so revving one near it's peak stock revs (7,000 rpm plus) while it's new is the equivalent of revving a 41.2 mm short stroked CRF50 engine to over 12,000 rpm when new ... Since the piston is heavier and has to travel a further 20 mm or near 50% more ... it has to go faster ... which means it has to stop dead and reverse direction from that higher speed in the exact same amount of time per rev ... The force is extremely high and causes the crank ends to flex ... the new metal has residual stress locked into it from manufacture ... That stress is gradually relieved over days , weeks and months of being heated up , run , then cooled down which in turn allows the parts to handle more stress without failing ... New cranks can easily fail in a long stroke motor ... In a previous thread I posted a link to a Thumpertalk thread where people were breaking brand new XR100 cranks that were stroked ... yet when "seasoned" cranks out of well used second hand motors were stroked , they were reliable when put through the exact same usage ... So the rider or user does in fact play a very BIG role in how reliable an engine will be and how long it will last ... After all ... motors don't break by themselves ... a new motor will last for hundreds of years sitting in the box until corrosion gets at it .... :p
 
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exactly....by the way its always soo funny to read newbiethings like : ooh bought a brand new engine and it broke after xxhours..my yamaha never did that to me ...chinese engines are sooo bad ..yadayada!! hahahaha...first off they obviously know zip about breaking in a engine , second they easily forget what they paid for this stuff ( lifan140 ..around 300 bucks..??) for that money for the whole engine ,you can´t get even a new flywheel for a yamaha and third even qualitystuff breaks occasionally ...specially when you don´t maintain it right!!
 
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what thread are you guys reading?

i cant remember whinging about lifans??

i cant remember saying lifans were expensive??

i cant remember saying other motors like yamaha dont break ???

i cant remember saying i over revved my motor???

ohhhh no dont tell me you guys followed me for the first six hours of riding with a tacho????

no but you are heaps cool man....you can post on forums...better then everyone else apparently?
 
What they are saying mate is, dont come on having a whinging fit about your cranks breaking :) happens all the time on PM.com and i think people start to get over it :p

on another note, bad luck with that crank, ive never had any troubles at all with the internals of my motors.... only thing ive managed to break was 1st gear on my jialing 182 build :)



good luck


Nate.
 
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