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CRF 450 Siezed Crank?

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So pretty much a weekend home went bad. I traveled home last weekend to go mess around with some buddies from back home. On the second day of riding all was good until the end of the day. In a table to stepup section I went to rail on it after the table and my bike completely locked up. A very abrupt metal on metal sound. I was told by my local mechanic that my rings fried causing my oil to blow out the air filter (which it did) then from lack of oil he guesses my crank locked up. Im active duty army and unless we are deployed we dont exactly make a killin'. My question is do you recommend me attempting to rebuild? I am somewhat mechanically inclined, have tools and manual, but dont have all the high speed bearing pullers and gear locks. Is this still do-able or no? I have read a couple good articles about the rebuild its just I didnt see much on how important the special tools are. Thanks for any recommendations.

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Understand that if in fact your engine went with out oil pressure you are looking at replacing crank,whole top end (head,valves,piston,cam,holder,buckets,cylinder), balancer bearings, oil pump and more. The tools needed to disassemble all this are not that special. Putting it all back together is the hardest part. The only way to learn it is to do it. Good luck!

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You do need a few special tools to rebuild the entire motor. Valve spring compressor for the valves, you will need to measure the bore of the cylinder and inspect it, also on the lower end you need a 20mm 4 prong tool (motion pro makes one for uner $10). Other than that, pretty simple stuff. Be sure to get a manual to help you step by step and have diagrams for when a spacer or gear falls off the tranny shafts. You will need it!

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Try to source an engine with low hours first. It might be cheaper and plus CRF engines are a dime a dozen

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a couple videos on youtube or rockymountainatvmc.com will help you a bunch. best of luck

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A fly wheel puller for around $20 and that special spanner tool for the balance shaft is all you really need. I got away with finding a old gear from a mini bike I fixed years ago and used that to stop the crank from rolling around while lossing and tighting the bolts that hold the gears in place under the right side cover. A shop manual or Clymers to get the torque specs from is good also.

We are the Airborne my brother.

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So its a bad day for the bike...i tore down today and found some serious problems. I took the head off and found the piston in two pieces. It slammed into the valves so the head is ruined, the cylinder wall has a whole in it. I havnt cracked the cases yet but from the top the crank doesnt appear scarred but we will see. My question is does it make more since to part my bike out and by another bike or buy one of those rebuilt motors off of ebayfor 1600 bucks.

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If it were me I would spend the money to fix the motor you have now. That way you'll have a better than new motor and not take a $1600 risk for one off Ebay.

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Try to source an engine with low hours first. It might be cheaper and plus CRF engines are a dime a dozen

THis is the best advice. You're looknig at some pretty darn big bucks wether you do it yourself or not. If you've never done, it you might find it's more than you want to get into once you've bought all the parts and are into the engine. I'd go on ebay or craig's list to see if I could find a good engine for it. THere are lots of guys who take perfectly good bikes and strip them down for sell on ebay. THis is a good way to get more for a bike than it's worth. Guys don't want to pay $6,000 for a 4 year old bike, but the engine might bring $1,500, the forks $800, etc. until the seller has nearly double thier money. Guys do it all the time, so your hopes of finding a good engine are high. When an engine is shot like yours is, this is going to be the cheapest course od action for you. Also, take your old engine apart and start selling the good parts that are left on ebay to help pay for your purchase.

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