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2001 YZ250 rebuild

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I recently purchased a 2001 YZ250 in need of a little TLC. According to the PO it just needed a new crank and had just had the top end re done by a shop. I went to check it out and even though the engine was in pieces and the everything was a little dirty, it looked OK so I took it for $800... A pretty good price for around here.

Here she is after I set out all of the engine parts on the bench and hosed off the bike.

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The bike itself was in pretty good shape once it was hosed off. It needed a brake lever, but I had a bent one laying around from my 250F. I plan on going through all of the wheel and suspension bearings to make sure they are greased and replace any bad ones.

I tore into the engine, and immediately two things jumped out at me. First was the crank bearing that went Tango Uniform:

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Well THERE'S yer problem! The crank assembly itself seemed in pretty good shape, and the play in the large end of the rod felt good, but I sent it to Mr. Crankshaft to get it rebuilt with Japanese parts anyway. More on that when it gets back.

The second thing I noticed was there was a chunk missing from the oring around the water routing hole!

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I don't see how this thing could have held any coolant for an extended period of time like this... Maybe it overheated and siezed and that's why the PO had the top end done? Would that also cause the crank bearing to go out or would that be a separate issue?

The bearings in the engine case felt pretty nasty, so I decided to replace all of them. Other than that, then engine looks pretty good The clutch basket and plates all look good, the clutch plates had a little surface rust from sitting but most of that wiped off and I soaked them in CLR just for good measure then hit them with WD40 while they wait. The piston and rings are indeed new OEM. The cylinder had been redone with 0 hours on it. The transmission is in good shape, it clicked through all the gears and the gears themselves are all intact.

Other than the crank and bearings it looks like I'll be in a gasket / seal kit, oil drain plug (I stripped the one tat was in it by using a 12 point socket :smashpc: layzyness doesn't pay!), and a couple of alignment pins for the cylinder if I can't locate them. I'll probably also discover some other small hardware I'm missing as I go along, too.

So far, so good. I've got most of the engine parts cleaned up and ready for reassembly once I get all the parts.

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That o-ring spits itself out no matter what. The two bottom ends I've done on my yz, the o-ring spit that part out within 5 hours. Just make sure to get some yamabond on the inner lip and you'll be fine.

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That's good to know!

I got all of the engine parts cleaned today and they're looking good. It's always a relief to see that a part or assembly doesn't need to be replaced!

I also removed the swing arm and rear wheel. Looks like the wheel bearings will need to be replaced as well as the linkage bearings. The plastic keepers holding the pins in the linkage roller bearings were breaking down and the pins were falling out! Unfortunate, but expected... At least the swingarm bearings seemed pretty good, they even still had wet grease! I'll probably just wipe it out and put fresh grease in them.

Aside from pushing out the suspension and wheel bearings, that makes teardown complete! I'm already anxious to get it back together and running...

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You said the cylinder has just been put back together..i'd make sure they put locktite on the three screws that go in the main shaft of the power valve system. The last 01 i did all three screws had fallen out,he couldn't figure why the motor lost power..

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Small update. Tonight I decided instead of replacing the bearings in the linkage, I would just pull out the plastic roller retainer and all the rollers, clean everything an re install all of the rollers with fresh grease. I used the lathe and some scotch brite to polish up the bushings and pivot bolts real well. I also flushed out the swingarm bearings, removed the thrust bearings and cleaned them, then re installed everything with grease.

Finally, I punched out the front and rear wheel bearings. They had a little life left in them but could stand to be replaced, so I will.

Here's the polished bushings:

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Polished pivot bolts:

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And here she is all stripped down waiting for parts to come in...

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Looking good... nice to see someone taking the time to be a thourough as you durring the rebuild and taking pride in thier work! Bike should be as good as new by the time you get done with it! Looks like a fairly low hour bike now that you have everything stripped apart.

Dont forget to oil that filter...:smashpc: j/k Good work!

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looking really good.

now i wish i woulda done a better job on my pivot bolts...i cleaned them up, but nowhere near that good.

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Yeah, well it helps to be able to throw them in the lathe and spin them up to 1500 RPM!

I enjoy working on this stuff, so sometimes I can get carried away with every little detail, but it usually pays off in the end.

And I'll get to the oil filter, right after I install the new cams!

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Yea We have a wood lathe but that's it. I do the same thing about the little details. That's why this budget build is gonna be a lil over budget lol

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Another small update. My order came in from the TT store, so I finally got to start putting things back on!

I got the wheel bearings put in and the wheels mounted back up.

I discovered that the Cometic complete engine gasket kit does NOT contain the oil seals.:smashpc: I don't know why I thought it did... Fortunately, the local dealer had all but the output shaft one in stock so I don't have to wait another week for parts to get here! The bearings should get here tomorrow, and the crank should be here on Monday. I found a new in wrapping 6001 bearing (water pump) around the shop, I had actually forgotten to order that one. All I had to do was peel off the shields and press it in. I polished up the water pump impeller shaft on the lathe and re assembled the water pump onto the case.

I cleaned up the carburetor and decided to replace the crusty vent lines with some new, blue line I had... Unfortunately 5 ft isn't enough, so I need to wait on TT order no. 2 for that. I also decided to order a new intake manifold, the old one was pretty cracked and the PO had gone to town with silicone trying to fix it...

Not much has happened, but that should soon change!

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Just got the crank back from Mr. Crankshaft. I have to say, he's a great guy to do business with! He answered all my email questions quickly, had lightning fast turnaround, and it looks beautiful! He rebuilt it with a Vesrah Japanese made kit for $170. I would highly recommend Mr. Crankshaft and will go to him again for sure.

Now I just need the other two bearings and I'll be able to put this sucker back together!

A note for any one in the Spokane area, I'll probably never be buying bearings from Motion industries again. They have proven to be pretty incompetent and slow. From getting the wrong parts, to sending me chinese made bearings, to taking longer to get my bearings than it took for me to send out my crank to KY, getting it rebuilt, and having it shipped back to me! Next time I'll be trying out Brown bearing!

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Yeah, well it helps to be able to throw them in the lathe and spin them up to 1500 RPM!

I enjoy working on this stuff, so sometimes I can get carried away with every little detail, but it usually pays off in the end.

And I'll get to the oil filter, right after I install the new cams!

you lost me . 2 stokes dont have oil filters and cams 👍

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👍

Oh yeah, I called them earlier and now Motion industries is telling me Wednesday to Thursday before the output shaft bearing comes in...

:ride:

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I've now been waiting nearly 2 months for my "local guy" to order parts in for me, so I feel your pain dude.

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dude that sucks man, yea brown bearing has never done that to me.

took both my yz's out today after a full carb rebuild and rejet on each and new pipes they ran great. ones suspension worked very well the other was WAY too soft for us me n my dad are both 225-250lbs

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Next update! You can read this grotesquely long commentary of the last 48 hours, or just skip to the pictures (It's OK, I probably would...)

The guys at Motion Industries proved themselves to be totally incompetent... I sent them an email on Thursday saying if they got the bearing in I'd just pick it up at their shop so I wouldn't have to wait for shipping. "Uh, we don't have it yet, and the tracking number they gave us isn't working.":banghead: So then I hatch the plan. I'll pick up the other crank bearing they were supposed to send me (I ordered two and they sent one:foul:) And then see if I can get the counter shaft bearing from brown bearing right up the street. So I call up brown. "Hmmm, that part number isn't showing up in our catalog..." ***? Great, so much for that plan. Well, I'm holding the Koyo bearing with this number so obviously they make it, so I give them the dimensions. A few seconds later "Yeah, we have one of those." SWEET! So I hop in the car and head over to Spokanistan. I stop by my good friends at motion first. "Here's your bearing." Huh, that looks a little small (o shi...). Uppon further inspection, it's the counter shaft bearing! Wait, I thought this was backordered??? "Yeah, that one came in, but we're still waiting on the other crankshaft bearing." W T F??? great, so there goes the plan again...👍 So then I head over to brown... Hey, I actually don't need that bearing, I need this one instead. "Well let me go check in the back..." Turns out they have one with two seals on it, and one with a snap ring on the outside but no seals. The one with the snap ring is almost 1/3 the price so I get that one (still a koyo bearing). Woo freaking hoo! Finally my quest to get my bearings is over!:worthy: I'll be going back to Brown bearing again for all my bearing needs, and Motion Industries can pound sand!:worthy:

OK, sorry for the rant / epic tale... If you are even still reading:smirk:

So I put in the bearings. The heating / freezing trick works like a charm! Time to put in the crank! So I start pulling in the crank with my improvised crank puller (two long blocks of aluminum, a thick washer, and the bolt that holds the drive gear on... Git er dun) Make sure con rod is out of the way... It's working well, but I need a bigger washer! Ok, round two... Dang, this is starting to get hard, I wonder what's the-- FFFFFuuuuuuuuuuuuuuuu! Con rod is caught on the case and bent way over:foul: FML I'm an idiot! Ok, don't panic, just press it out. Why isn't this working??? Oh, the crank isn't fitting between the platform on the press, that's why you used those blocks last time YOU FREAKING MORON!!!:ride: Good job, in less than an hour you've managed to completely F up the crank you just got rebuilt...

Well, in my tired frustration, I decided there were two options. 1) kill myself! 2) fix it. Obviously I opted for the latter. So I took the crank assembly over to the milling machine and with a combination of some spacers and the machine vise, I manage to un screw the con rod. It's looking pretty good now, but the crank is still tweaked thanks to my lapse in intelligence combined with force multiplying equipment. So I throw the four-jaw on the lathe and get the lathe side of the crank dialed in to less than half a thou (My barrel cambering days are starting to pay off!), then I put the indicator on the other bearing surface. Yep, it's way off... Time for the rubber bang stick! A little while later, and I have a crank that's trued to half a thou give or take a few mils. Woot, pooch un-screwed!

Finally, I get all the parts of the inner case in, including the !@#!$@#!#ing transmission assembly. Why don't the forks just slide on the pins, instead of having the whole pin slide in the case??? Then it would not only be easier to install, but it would be steel on steel wearing instead of steel on aluminum! Whatever, it's like 10 PM and I am going to finish this motor if it kills me!

OK, goop up the case halves, install dowel pins, and slide the other case on. Wait, why the heck isn't it going that last 2 mm???:worthy: Tap with mallet... Still nothing... Tap harder with mallet... ***? pull off case. What its it catching on??? Fast forward about 45 minutes and I still can't figure it out, every thing looks fine but now the sealant is dried... Great, so I scrape off all the sealant, apply more goo, check everything for the millionth time/ It's going to go on now. I can feel it! Or not... Still hung up on that last little bit. By this time I'm tired, frustrated, intoxicated by rage and I've probably used every colored word in the dictionary and probably invented a few. So now it's time to violate one of the cardinal rules of working on anything. You'll probably cringe when reading this, but I threw in all of the bolts and started to tighten it down. I'll FORCE it! Well, amazingly I got the halves together, torqued to spec, and didn't pull the threads out of the case! Crank spins freely, time to test the shifting. What the... It isn't working? (see other thread about shifting problems) Well, by this time I've had it. I pull the case half off, clean off all the sealant, look at the transmission and can't figure out why it isn't working... Then I look at the dowel pin. What the heck? It's all squished looking-- oh crap!

For some reason that is beyond me, in between the case halves, there are two holes that look like they are there to put dowel pins into... Not the large dowel pins that you put in between the case halves, oh no, these ones perfectly fit the dowel pins for the clutch side case cover. What in the blazes? Yeah, in my haste to finally put my motor back together and already distracted by my cluster fail on the crank, I looked right at those holes, grabbed the wrong dowel pins and put them in the mystery holes without giving it a second thought. No wonder the cases weren't going together! :worthy: I still have no idea why those holes are there... So Tired and defeated I call it a night. What a cluster fail!

Next day (Friday) Try not to be such a moron this time, OK? I still don't know what the deal was with the shifting, maybe the cases were misaligned because of the pin pressing pillock (That's me)? I settle for greasing the shift fork shafts and trying again -- "this time without the oops!" It's amazing how much better it works with the CORRECT parts in place:bonk: BUT THERE'S STILL A SHIFTING PROBLEM!!! What is a guy to do? Post a question on TT! By the time I had re-done the vent tubes on the carb, I had a reply. Apparently it is normal and will go away once it is fulled with some oil. Whew, well at least it made me take apart the cases and find my dowel pin problem! Think optimistic thoughts!

I got all the rest of the parts in without much trouble, although tightening the clutch nut without a clutch holder tool can be quite cantankerous! Time to install the clutch side cove -- oh wait, you FUBARed the dowel pins... And the dealer doesn't have any... Time for the lathe, and the will to use it, to save the day again! Two new dowel pins, hot off the er, lathe! Here you can see then alongside the old ones so you can giggle at my pain.

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And there was much rejoicing... yay...

Well, now it's all together. I am missing a couple pieces of hardware on the flywheel side, hopefully the dealer will have those or maybe the fastener store... I was so happy after getting this thing together, I carried it into the house to show everyone! I've never had a engine build this messed up before. Hopefully it isn't an omen!

Here is the engine before and after pics!

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ta-freaking-da!

Hopefully if you actually read all of that, my misery brought you some form of entertainment, or at least showed you some things NOT to do next time you build an engine!

If all goes according to plan, Tomorrow I just need to track down the hardware, set the timing, fill it with oil, install it in the frame, and run it!!!:worthy:

And why does this website censor "Whiskey Tango Foxtrot"? I didn't realize acronyms of vulgarities were vulgarities themselves... But FUBAR is fine? Whatever...

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