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My brothers 450

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So this is my brothers 2012 CRF450 he just got brand new from the dealer last February.... 94HRS oil changed every 6hrs, air filter changed every ride, always cleaned and well taken care of... And those of you loyal to OEM... It's NOT always perfect either. Even when put in by the factory... The piston seized to the cylinder.. YES it had coolant.. We run only engine ice. The piston seizing caused the connecting rod to snap off and go through the bottom part of the cylinder and also through the cases... This is just bad luck if you ask me... I don't know what else to think... Figured I'd post them for you guys to ponder with me for a bit.

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Damn thats going to break the bank..

yeah he's $500 in the hole with the cases alone.. A new OEM crank is going to be about $300.. Then piston and rings and he should be good to go. He got lucky because the valves and everything else was perfectly fine and untouched so he dodged a bullet there

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There weren't any in it the last oil change which was 2hrs previous to this. I'm just kinda stunned by it... No warning signs, no neglect.. I just don't know... The only thing I can point the finger at was that he probably should have put a new piston and rings in it at 50hrs along with a cam chain... I don't know if that would have prevented this or not.

It's not even my bike and it bums the shit out of me. I have the same bike as him because we bought them as a pair so I'm hoping I never have this problem. I'm only at 38hrs on mine though because I work a lot lol but when I get to 50hrs it's getting a new piston, rings, and cam chain and hopefully I'll never have this problem. He was lucky he was across the road from our house when it happened

Edited by Emkjr93

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Well I finally got a chance to personally look at the bike.. The piston did not seize... The connecting rod just basically exploded where it connects to the crank bearing. Atleast it didn't do any harm to the valves or anything up top. Cylinder, cases, crank, and piston are all done for though. It'll probably be around a $1200 rebuild if we're lucky.

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Well I finally got a chance to personally look at the bike.. The piston did not seize... The connecting rod just basically exploded where it connects to the crank bearing. Atleast it didn't do any harm to the valves or anything up top. Cylinder, cases, crank, and piston are all done for though. It'll probably be around a $1200 rebuild if we're lucky.

how does he ride the bike? If he's hard on it that will happen in time. I have an 06 crf with over 100hrs on stock crank and it's still good but I don't ride it hard and keep it out of the high Rpms. I've seen a few bikes explode the bottom end like that and all were race bikes or were abused like one.

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There weren't any in it the last oil change which was 2hrs previous to this. I'm just kinda stunned by it... No warning signs, no neglect.. I just don't know... The only thing I can point the finger at was that he probably should have put a new piston and rings in it at 50hrs along with a cam chain... I don't know if that would have prevented this or not.

It's not even my bike and it bums the shit out of me. I have the same bike as him because we bought them as a pair so I'm hoping I never have this problem. I'm only at 38hrs on mine though because I work a lot lol but when I get to 50hrs it's getting a new piston, rings, and cam chain and hopefully I'll never have this problem. He was lucky he was across the road from our house when it happened

Unless your brother is constantly bouncing that thing off the rev limiter I doubt that the piston caused the rod to snap. The later models haven't suffered rod failures to any great degree. Its very unfortunate that it happened and I hope your brother didn't get injured when it let go. You don't need to panic over yours. I suggest you replace the piston on your bike between 60-80 hours but again I don't believe that caused the rod to fail.

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My brother rides it pretty hard but he's never on the rev limiter. I also looked at the cylinder and piston earlier and I said it in another post more recently that the piston did not seize, it looked like the connecting rod just decided to blow apart where it connects to the crank bearing.. But anyways, I figured he would have been able to get a lot more time than just 94hrs for the engine to do that... Really sucks :(

He didn't get hurt when it decided to let go. He said he was about to go up a hill and when he cracked the throttle open, he heard a loud clank and it was all locked up.... I know you guys said not for me to worry about mine but it's hard not to lol like I said I'm only at 38hrs on mine but still lol

Edited by Emkjr93

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I would never go more than 40hrs on a crank. Learned the hard way

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I would never go more than 40hrs on a crank. Learned the hard way

I think 40hrs on a crank is going waaay overboard, exploded connecting rod or not, I think they're designed to last a lot longer than that lol I don't have $300 to dish out every 40hrs or else I would do the same honestly.
  • Like 1

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40 hours on a crank?!?!?!  seriously?  id be replacing mine every 2 months if that was the case in the summer.  someone like melk man would be doing a crank every week.. :p

 

I got 380 hours out of my 05 crank, the only reason it finally seized is because im an idiot and crushed the oil passage hole while removing the flyhwheel, but replacing it every 40 hours wow.  you must replace your piston every 20 engine hours??? aka every 2nd weekend??  thats a little overkill.  at that rate it would be cheaper to let er blow and replace the whole engine at $1500 every 5 years versus a $400 crank every 3 months for 5 years.....

Edited by cdf450

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All depends on the type of use. Racing is a different animal than trail riding.

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Just for the record, my manual says to replace the piston and rings every 15hrs... Yeah I'm not gonna do that.. It can wait till 50hrs and then I'll replace the piston, rings, and cam chain lol I've had my bike over a year now and only have 38hrs on it. I ride a lot of track and raced once this year so I'm thinking 50hrs would be a good time to do it.

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All depends on the type of use. Racing is a different animal than trail riding.

 

Absolutely. And the intended use for these bikes is motox racing.

Trail riding, the crank might outlast the bike, and as many have reported here, hundreds of hours of service life.

I would still make crank service a regular service item. Its not a lot of work. and a complete crank replacement can be done for a few hundred dollars.

When they fail it makes a mess as you can see here.

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Absolutely. And the intended use for these bikes is motox racing.

Trail riding, the crank might outlast the bike, and as many have reported here, hundreds of hours of service life.

I would still make crank service a regular service item. Its not a lot of work. and a complete crank replacement can be done for a few hundred dollars.

When they fail it makes a mess as you can see here.

Not a lot of work?  Dude it's a ton of work, a lot less than picking up the broken pieces when a crank lets go, but come on you have a lot of free time if you don't think replacing a crank is a lot of work.  Scraping the old gasket off all the surfaces probably took me at least an hour alone.

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I might be wrong but doesn't the manual state that the oil be changed at 15 hours also?

I believe you might be right, I'll have to check. If so, I'd find it pretty weird that every time your due for an oil change a new piston is due as well... "Yeah it's time for my routine oil, oil filter, piston and rings change now..." Probably could go longer than 15hrs on a tank of gas lol

Just checked and confirmed, you are correct! Says oil change every 15hrs too! What the hell? Does it actually expect us to do this? You'd never get past the break in stage lol maybe if I was an A class rider with a ton of money I would do that but I'm just a normal guy that has to work for his money and only has a little bit to left over after paying bills lol

Edited by Emkjr93

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