2003 YZF250 parts question

Hello, I didn't see a "new members" section so I'll give a quick introduction. My name is Clay and I started riding minibikes around 10 years old. This progressed through a XL100, XR200, CR125, XR250, CR250 and finally to a 87 XR600 I recently purchased. Recent hobbies are building and testing dragracing / street cars - most recent is a twin turbo setup on my Nova. Anyway enough of that. I have already searched and found a lot of information but have a few quick questions. I recently purchased an 03 YZF250 that has an Athena 290 kit - also Yoshimura exhaust. Now being 40 I really need this like a hole in the head but for $400 I couldn't turn it down - figured I could piece it out and double my money worst case. Previous owner said it locked up. When he took the head / cylinder off it wasn't locked up anymore. Piston, cylinder, cams, valves, cam chain all look great. Then it sat for several years. Now knowing he most likely rode the crap out of it, I'll replace the crank for sure. Now are you guys using a factory Yamaha crank, rebuilding the factory crank or using an aftermarket crank? What's most preferable from durability and cost? I'm also thinking maybe a transmission problem so I'm going to split the cases to be sure. Anybody had any shifting fork problems other than the fork wear from trying to go to "6th" gear that isn't there. Any other potential causes to look at when I tear it down. Got a few things to finish up and it'll take me about a month to get to it - just doing some research first. Sorry for the long post - I tend to ramble. Thanks in advance for the help. Clay

Not at all. Sometimes they will lock up, and all it is, is the PO torqued the cam caps too tight. That would explain why it freed up when the head came off. I'd only replace the crank if the rod is moving sideways. Evaluate the tranny only after you get it back together and running. Shift it thru the gears with the top end off, and make sure it will change both up and down. If it does, I'd say you're good.

O.k. - another area to look at. One other thing - does the Athena kit use specific base and head gaskets or will the factory one's work? It doesn't look like the cases need to be bored to accept the liner so I'm at least thinking the base will work. Depending on the head gasket design I'm thinking it may be large enough, can be enlarged or if it has some sort of fire ring - then not. Sorry for the goofy gasket question - I haven't really looked at any of this stuff yet, I've put it all on a shelf for later - hopefully in a month or so I'll have time to get on this. Thanks again. Clay

According to Luke at Luke's Racing you must use Athana gaskets on an Athana 290 kit.

Thanks, once I get into it I'll probalby have some more questions. Great site by the way. Clay

Got some time to tear it down to see what caused the problem. Intake cam journals looked good with no signs of seizure or galling of any kind. When I got to the crank and spun it a few times it felt good for about half a dozen turns and then developed a "catch" for lack of a better term. Also noticed this which is pretty much the nail in the coffin. I'm not sure but I would think even if they heated the crank to install the pin, they wouldn't heat it that hot or that unevenly. Cam chain sprocket looked pretty rough too so it alone would be a reason to replace the crank.


During teardown I also noticed the oil pump was very tight. It also only had one bolt holding it on instead of the three it should have. I didn't see any signs the previous owner had removed that crankcase cover and did'nt find them in the engine anywhere so I don't know what happened there. The oil pump looks fine and once I cracked the one bolt loose it turned beautifully. I'm still wondering maybe an oil starvation issue? I ordered everything (hopefully) to put it back together from the TT store and so far all that seems to be missing is one cam chain guide and the external oil supply pipe and associated hardware which is better than I expected. Clay

Yep, that's your sign. PO liked to run it on the rev limiter, probably a kid. Replace the crank and crank bearings, replace the oil pump because it will be scored, pull the screen and clean it, pour cleaner down the frame tank and clean that out, and clean out all oil passages, filter housing and lines. Blow it all out with brake cleaner and compresses air and catch residue to verify no metal is coming out. Replace the cam chain and sliders, clean the back side of the flywheel and get all metal chips off of it. Check all tranny bearings while its split, check the shift drum and forks for wear and replace if worn or bent. Check the clutch basket for grooves worn in it. You can do that much yourself for about $500, $850 if you have to do the valves too. Sometimes you can find a usable crank, but new is better, Hot Cams for around $200.

You pretty much layed out my game plan exactly. Have a new crank on the way with new bearings. One cam chain guide that was missing, other looked almost perfect. There wasn't very much metal anywhere, even in the filter. It looks like the seizure happened pretty quick once things started going bad. I'll look at the pump on reassembly. I'm waiting on parts for other projects so tomorrow I'm going to wash everything associated with the frame - oil tank, lines, etc. and of course the frame itself. I'll start another thread once I start putting it together to show anything else I run into so maybe others can learn. Clay

Crank bluing is normal. Yes, they do heat the crank and press it together in a jig, then a few taps with a brass hammer to make the alignment perfect.

Does the rod move smoothly? Is there any vertical play (side to side is normal)?

Bolts missing? Cam chain guide missing - Yikes! I would carefully look at every page in the parts fiche for your engine and ensure every part is accounted for.

Rod had tight spots in it. It would turn pretty good for half a dozen revolutions then get tight. Back it up and good for another half dozen, maybe ten and then the same thing. I bought the bike as a basket case (actually not bad as basket cases go) and I expected a few missing parts. So far cam chain guide and oil supply pipe are only things m.i.a. Actually this the first basket case I have bought - looked at a few but they were too bad - one was a basket case among three other basket cases. I'm a glutton for punishment but that one was far too much. Clay

Ohhhh I thought the engine had been assembled and this is what you found as you took it apart. Just watch what you spend Vs. what it is worth

Yeah, I hear ya. That's always the gamble and why I have never bought a basket case before. So far with the purchase price and the parts to get the engine back together I'm at $825. It needs a new chain as it has a non o-ring on it and I'm not going back to that so that's another $100. Also needs an air cleaner as the current one is rotten of course. I figure I'll have to put fork seals in it once I start riding so my plan is to be around or slightly over the $1000 mark.Clay

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