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ThumperKid250F

yup i did it i blew my 450up

15 posts in this topic

just what it says up top i blew the motor on my 450 this weekend ice racing,:)

i came out of the one corner in 3rd and got on the gas and right when i got on the gas the motor made a loud noise like my chain was spinning on my rear sprocket kind of noise, then i lost all power. so as soon as that happen i pulled the clutch in and shut her down. i tryed to kick start it and it had no compression at all and then the kick started just locked up and now it wont move at all..:smirk:

im going to be pulling the motor out this weekend and going to pull the topend apart to see whats going on in there.. i already pulled the valve cover off and i see nothing, also the spark pulg is not crushed..

im thinking i might of blew out my crankbearing or my piston just failed..

any thoughts

2006 yz 450

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Did you jet it for the cold air and the high revs? What kind of oil you using?

That SUX man.

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yes it was jetted pefect for the cold air and everything, bike ran like a champ all season, i changed the oil after everyride and when i blew up it only had about 10 laps on her so the oil wasent even broken down at all..

i think she was just a little upset i got a 2007 yz 250 smoker in the garage so she decided to take her own life...

BTW the oil was rotella syn

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yes it was jetted pefect for the cold air and everything, bike ran like a champ all season, i changed the oil after everyride and when i blew up it only had about 10 laps on her so the oil wasent even broken down at all..

i think she was just a little upset i got a 2007 yz 250 smoker in the garage so she decided to take her own life...

BTW the oil was rotella syn

Damm thats the oil I use. :smirk:

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Damm thats the oil I use. :smirk:

it wasent the oil that made the bike blow up.. i got the motor out of the frame and im going to be taking it apart in the next couple hours so ill let you no what happen.. like i said befor i think i blew a ring or the crank bearing went...

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ok well i took her apart and i found a couple things :smirk:

1 wrist pin is snaped in half, and the one half was down inside the cases..BOTH circlips were still on the piston

2 cilinder is cracked in half with a big peice missing somewhere in the motor

3 piston was cracked

4 it looks like a valve or two hit the piston

5 top of the crank is all messed up..

6 on the oilfilter side theres tab that is broken off in my case..

so im looking at a good amount of work to be done...

any ideas on why the wrist pin would just snap like that ?

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hi.. thats suck man..

how many hours?

did you do your preventive maintnance?

where from jersey?

well good luck, if there is any thing i can do to help you let me know(other then money, becuase if thats what you need i'm the wrong door to knock on:) )

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Without seeing it it is hard to tell. My guess would be too much time on the top end. How many hours were on the piston?

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That doesnt sound good at all. Sorry to hear the bad news but have you checked your valves recently? I guess thats the only thing I can think of.

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1 wrist pin is snaped in half, and the one half was down inside the cases..BOTH circlips were still on the piston

any ideas on why the wrist pin would just snap like that ?

I can't think of anything that would cause it to happen. :smirk:

Probably just a pin with a micro-fracture from the factory and it took a while to break. :) Not impossible to happen that way, but very improbable.

I can definitely see how the pin breaking can cause all of the other damage though. That really sucks and it can't be very cheap to fix. :ride:

Are you going to try to find a complete engine on eBay or work with what you already have?

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ok well i took her apart and i found a couple things :smirk:

1 wrist pin is snaped in half, and the one half was down inside the cases..BOTH circlips were still on the piston

2 cilinder is cracked in half with a big peice missing somewhere in the motor

3 piston was cracked

4 it looks like a valve or two hit the piston

5 top of the crank is all messed up..

6 on the oilfilter side theres tab that is broken off in my case..

so im looking at a good amount of work to be done...

any ideas on why the wrist pin would just snap like that ?

I have seen kx 450 f piston pins snap but never on a yz. How many hours you think were on it?

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the piston only has about 10 hours on it and it was a wiseco HI comp piston..

i talk to some vet ice racers in town and they said the pin could break from from the hi revs on the ice

the motor it self only has about 40 hours on it and the valves never moved since new, always in spec.

also i always keep my bikes in top shape, change the oil every 2 rides on the dirt and ice racing i change it everyride with oil filter , the airfilter is changed after everyride also.

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I can't think of anything that would cause it to happen. :smirk:

Probably just a pin with a micro-fracture from the factory and it took a while to break. :) Not impossible to happen that way, but very improbable.

I can definitely see how the pin breaking can cause all of the other damage though. That really sucks and it can't be very cheap to fix. :ride:

Are you going to try to find a complete engine on eBay or work with what you already have?

im going to work with what i have, not really sure what im goign to do with the motor, thinking of making it into a pure iceracing/flattrack motor..

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