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'03 CRF450 motor locked up rebuild opinions

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The engine on the '03 450 I just bought is locked up. The guy I bought it off of said he was riding on gravel for about 5 minutes and it acted like it was out of gas and died. He kicked it over a couple times and it started and rode for a minute or two more and it happened again but this time when he tried to start it, it was locked up.

So I buy it for cheap, get it home and it's definetly locked up. I pull the plug, spray some lube in there and put it in gear and rock it back and forth and get it to free up. However when kicking it over it will hit make a thump and then stop. I'm assuming it's hitting a valve I've got as far as pulling the valve cover but haven't really had time to look and see if it's dropped a valve. The timing marks all line up, but could it somehow be off enough to do this? I also pulled the oil filter, it was a little low on oil but not enough to blow the motor I don't think, but there was alot of metal or aluminum in the oil. I tried to pick it up with a magnet but I think with it being all oily if it was metal it wouldn't pick it up so I don't know if it's aluminum or metal.

So as of right now I'm thinking it just locked up the piston. I know the piston and/or rings have never been replaced but this is a incredibly low hour hour

bike probably less than 50 hours on it since new, he'll it's still got the original tires and grips. Does anyone agree, disagree? Anyone ever have a similar problem I have no problem doing a complete top end job but don't feel comfortable doing the bottom, much less have the funds to do a complete rebuild.

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If there is aluminum in the oil filter thats a pretty bad sign. If I were you, Id get the manual (the real shop manual) and pull the motor apart and just see where exactly you stand. Guessing at what might be the problem is silly.

There is tons of info on this site. If you do a search, somebody here has the manual that you can download as a PDF file I think.

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I've had the manual downloaded but it's a pain to have to go upstairs to the computer every time I need it but just bought a laptop so that'll help. Was hoping someone with more thumper experience might help out.

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What do you mean more experience. Being a Moderator with over 11 thouands posts is not enough for you.I will do you one better. My brother used to be an auto tech now a truck driver,My mom calls him on the phone with a engine problem and he says hold it up to the phone I will let you know. So post a pic of the engine I will let you know exactly what needs to be done,LOL. Engine needs to be taken apart. I bet you thought the guy you bought the bike from just did not know how to start it and for 400 bucks wam bam you would get the bike running and make a bundle. Unless you can do the work yourself could cost close to 1,500 or more. Good luck.

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making 11k+ posts doesn't make you an authority on anything except posting. it points out the fact you spend all of your time on the computer when you should be outside riding. do i need to state that i'm joking? probably, because someone might think i'm serious.:moon:

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I know posting doesn't make you an authority but in this case Shawn does know a little something. I dont know him personaly but after reading his posts over the years I got quite a few good tips. Yes you do need to state your joking you know how people get.:cheers::moon::smirk::banana: Just kiddin. But the engine does need to be taken apart dont you agree?

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Well...unless you take the damn thing apart, you wont know shit. :moon:

If you're intimidated about the idea of tearing into it, just say so. There's nothing wrong with that. But Im hear to tell ya, its not a nightmare or some exploding riddle in there.

A buddy brought over his KX250 a while back and told me it needed a complete rebuild because it was clanking so bad and wouldn't hardly move.

I fired it up and it clanks...but its just the damn pipe against the frame. And it wont move because the rear wheel bearings are rusted solid. The clutch basket is toast and so is the hub, so it'll get a new top end, basket and drum with a clutch kit and its done. So instead of dropping 200 on a crank and all the bearings, and a bunch of other he wont need, he'll be riding with fat wad of cash still in his pocket. Fat wad of cash or not, he'll still be eating my roost! :cheers:

How do you think I figured that out? It wasn't by gleaning things from 4 feet away from it and scratching my chin.

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Well I'm gonna pull the motor over the holidays when I have some time off. Start with the top end first, and no I'm not scared! The bikes kept at my folks not at my place and with work not much time to do anything to it. I didn't buy it hoping to make a bunch of money just to hopefully have myself a thumper without shelling out $3-4k upfront.

I will be pulling the motor soon and want to make sure I have all the tools before hand, so anyone know what size(s) I'll need for the swingarm nut and bolt?? Also I was wondering how to get the exhaust stud closest to the frame off I seem to remember it being pretty tight in there and was thinking I might not be able to get a socket on there. Any other things I might need to know about getting the motor out? I'll probably pull the top end first just to make it easy on myself.

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These engines are super easy to take apart, it's the re-assembly that takes patience and some technical prowess. Good news is you got in cheap and can do a little learning while you figure everything out.

Have you ever tried to fix an automatic transmission in the dark ? That's about what are asking us to do, w/o having the engine torn down...We would all be guessing !

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You dont need to remove the engine from the bike to get the head off okay bud! I you lived close I would help you and show you how it is done with out a charge. It is pretty easy. Give me a call and I will hook you up with a tool set for a great price. I sell tools for a living. If you would like. I can even go over it with you on the phone if you like bud. I am not being push just trying to hlep! Okay. Pm me and we will get this started. Dont mind these guys they havent had their bones today.

Flyn Ryan Menke

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Removing the top end to make it easier to take the engine out. But thank you for being nice seems like people are awfully rude on this forum, I know I should shut up because it will bite me in the ass, but all I wanted to know was if anyone has had a similar experience. Obviously I will have to pull the motor apart, I know this, I will, when I have time. I work ALOT, sometimes it's a good thing sometimes it's not. I will report back the day after Christmas with any findings, so that tells you what I will be spending my holiday doing!

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Ok so I pull the oil filter and find a bunch of shaving, not sure if aluminuim or metal. Tried picking them up with a magnet but I think they were too oily.

photo1.jpg

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So here's what the plug looked like. Not the best shape but no indication of anything wrong with the top end. Also color looks good to me, however I am more of a 2 stroke guy so correct me if I'm wrong.

photo2.jpg

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Here's the head and the piston. The piston has obviously made some contact with the valves. I poured some cleaner down the intake and exhaust ports and only one intake valve leaks, just a little bit. Actually took about 5 minutes for anything to leak out of it. The piston skirts look good and the rings looked good, however and didn't take the time to measure them.

photo7.jpg

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Here's the wrist pin which feels as smooth as can be but has some obvious discoloration.

photo5.jpg

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And here's the cylinder which has excellent cross hatching on it but it's gonna need replaced because it has some gouging that's pretty bad.

photo3.jpg

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And unfortunetly the problem is in the bottom end. The big end of the connecting rod is trashed. It will spin freely until it hits a certian spot and then it locks up. The oil and filter were changed on this bike less than an hour before this happened, and I measured the oil after I drained it to make sure it had the correct amount which it did. Don't know why this ended up happening other than running it WOT too long I guess. So now I have to decide whether to do the bottom end myself or have a shop do it. Oh well if I have to spend $1000 I'll still be coming out alright!

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hey just give these guys a call they will do a complete engine rebuild bottom top and valves. its like 1400 that includes labor and normal wear parts like piston crank valves. plus shipping probably cost you 200 both ways depending on where you live, but that is still on 1600 not bad depending on what you paid for the bike. their web site is fastheads.com and there number is (435) 668-7776

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Well I talked to a local shop, probably the only one around I would trust. he said if I bring in just the bottom end it would cost $500-550 so that's probably the route I'll go. Spook should I put in another stock crank or go with an aftermarket crank?

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do it yourself bud! you're already halfway there and if you do it all yourself then you can get yourself a new piston/rings, cam chain and other stuff for the same price. I did this myself just last year and I was a little apprehensive about the whole thing but decided the bite the bullet and give it a go (partly due to encouragement from TT members) and not only did I save a buttload of cash but I pretty much know the ins/outs of how my bike works and the bike runs like a champ. just be careful, if you do this then all your buddies will be bugging you to work on their bikes afterward. haha good luck!

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