preston193 Posted March 24, 2010 I bought an 05 CRF450 this weekend with a seized motor, dont worry I didn't pay very much. I bought it with the intention of rebuilding the motor myself or parting out the bike to get my money back. I opened the top end tonight and found this The obvious to me is that the cylinder, piston, and valves are toast. I also know that the bottom will need to be taken apart and cleaned at the least. I have a couple questions though. 1. How bad do you think the bottom end is and what could be damaged from pieces of the piston? 2. Is the head salvageable with a few dents from the piston? 3. I paid under a thousand for the bike, is the bike worth fixing? I dont have 3 or 4 thousand to buy another bike. Rebuilding the motor would stretch my current budget. My 03 was stolen three weeks ago and my wife has been kind enough to humor me on this project. Thanks for any help you can give. Share this post Link to post Share on other sites
tubthumper85 Posted March 24, 2010 Just a new set of rings and you should be good to go!!! haha jk. Never seen one that bad before, I think you have to split the case to really see how much damage has been done. Looks like a lot of the piston might be in the crank case, hopefully it didnt mess up the case. I would at least plan on new crank/bearings maybe more?? As for the head I dont see anything to serious besides the valves. Could probably be cleaned up and used again, if you had seats recut w/new valves. By the looks of it the guy you got it from wasnt much for keeping up on maintenance and if it was mine that I planned on riding I would just plan on new head, cylinder, and crank so you start fresh. Sad to hear someone stole your bike, I had one get stolen in Vegas. Dont people know better than to mess with a mans bike? Share this post Link to post Share on other sites
BigRichard Posted March 24, 2010 Wow - I would guess that he seized it at somewhere around 2 million RPM. Share this post Link to post Share on other sites
YZFan Posted March 25, 2010 I have seen stuff like that in diesels but never on a bike. That is crazy Share this post Link to post Share on other sites
CamP Posted March 25, 2010 That's what a very worn out slipper piston looks like when it cocks sideways in the bore. The crank is toast too. Budget about $2k for a rebuild or ebay engine. If you don't have $2k, start parting it out. Personally, I would get rid of it. Share this post Link to post Share on other sites
MotuL-Man Posted March 25, 2010 Is this one of those new LOW comp pistons? Share this post Link to post Share on other sites
crawfishoo Posted March 25, 2010 If you do the labor yourself you could get it done for 1200 ish. Same thing happened to my buddies 04, piston turned straight up. Said and done he spend $1150. This is what we replaced Hot rod crank assembly and bearings cylinder piston & rings head faction mx intake valves stock exhaust valves cam chain cam chain tensioner gasket kit A & B Find a good dealer that will work with you on parts or shop around online for things. If you can not spend 1200-1500 dollars and do the labor yourself I would part it out. Share this post Link to post Share on other sites
bajabunk Posted March 25, 2010 How did the chain look? Share this post Link to post Share on other sites
preston193 Posted March 25, 2010 The chain was real loose and the pipe is really loud. Everything in the bottom is moving there is just a lot of debris from the piston and cylinder. I'm going to be pulling the motor out and splitting the cases hopefully by this weekend. I'll get some more pictures up soon. Can someone recommend a bottom end rebuild kit. Share this post Link to post Share on other sites
BigRichard Posted March 25, 2010 and the pipe is really loud. How can you tell how loud the pipe is? Share this post Link to post Share on other sites
bajabunk Posted March 25, 2010 How can you tell how loud the pipe is? I hope this guy is kidding:bonk:👍🤣 Share this post Link to post Share on other sites
XC-Kx250 Posted March 25, 2010 I wouldn't even think about spending $1 on the motor without a new crank. Even if it does still move freely, the rod will be toast at a minimum. But all in all you can easily get it back together for $1500. Share this post Link to post Share on other sites
jeffgoodtime Posted March 25, 2010 Is this one of those 2 stroke 4 stroke combos? lol. There is a good chance the rod is bent from the quick stop the piston had, and your valves may have to be cut out of the head. If i were you i would part it and find a lesser of a project. And i think i would go back to the guy that sold this to you and kick him in the butt.👍 Share this post Link to post Share on other sites
crawfishoo Posted March 25, 2010 I think wiseco make a whole bottom end rebuild kit, complete with crank, rod, bearings, and all the seals and gaskets needed. http://www.wiseco.com/PDFs/Wiseco-BottomEndKits.pdf This is an old page but will give you an idea of whats avaliable. This page does not show the CRF but I have seen them in the parts unlimited catalog, so I know you can get one. Share this post Link to post Share on other sites
BigRichard Posted March 26, 2010 I hope this guy is kidding:bonk:👍🤣 Not kidding – I might be slow though. What pipe is he talking about? Or did I just miss a joke somewhere? Share this post Link to post Share on other sites
SIERRA 13 Posted March 26, 2010 How can you tell how loud the pipe is? I thought the same thing! LOL 👍 Share this post Link to post Share on other sites
BigRichard Posted March 26, 2010 I thought the same thing! LOL 👍 The chain was real loose and the pipe is really loud. I'm prepared for you guys to make fun of me, but I still don't get it. I assume he is talking about the timing chain but what pipe could be loud? The bus I rode to school was 25 to 30 ft long so I think I'm okay in that department. Share this post Link to post Share on other sites
Santan9 Posted March 26, 2010 I hope this guy is kidding:bonk:👍🤣 why would he be kidding? OP said the pipe is loud, the guy asked how does he know its loud. I assume hes asking "how does he know" because the engine is blown up/not able to run. how do you assume that the pipe is loud on a bike that doesnt run/has exploded? THATS why he asked "how do you know its loud", right? doesnt take a rocket scientist to figure that out... 🙂 Share this post Link to post Share on other sites
preston193 Posted March 26, 2010 the pipe reference was an inside joke between me and my cousin. I have no idea about how loud the pipe is. Share this post Link to post Share on other sites
Santan9 Posted March 26, 2010 the pipe reference was an inside joke between me and my cousin. I have no idea about how loud the pipe is. lol oh ok, now that I read it along with your loose chain I can see how it is sarcasm/a joke. but yeah, like others said, you can have this fixed for 1500$ if you do your own work. im sure you can easily do most of it, the crank might be a little tricky though. or maybe im just saying that because ive never done one and it intimidates the hell out of me! piston + cylinder + gaskets = 350$ top end = 600-700$ crank - 200-250$ Share this post Link to post Share on other sites
