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2007 YZ250 - Guess the condition

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Hey all,
 
Picked up a 2007 YZ250 in awful nick (externally) for cheap. I'm not very mechanically experienced below the cylinder (have done a 4T top-end before) and don't have the tools to split the cases, so I'm putting this out there in the hope that some more experienced mechanics can advise me.

  • Reportedly 1 owner
  • Reportedly sitting for a few years due to hand injury (covered in dirt, tyres flat, grips eroded away into some kind of blue goop)
  • No hour meter
  • Spark plug brown/black on removal
  • Carby bowl gunked up but main jet OK
  • Clutch baskets notching not tactile (pictured below)
  • Clutch plates not discoloured or warped
  • Piston head free of damage (pictured below)
  • Cylinder free of gouges and tactile scratches (pictured below)
  • I had the PO start and ride it before purchasing. Started in a couple of kicks with old fuel, ran OK, went through some gears, power wheelies with 14/45 (3.21) gearing suggests not sluggish?
  • No obvious knocking in the short time I ran it at home

Based on this information and the follow pictures, am I safe to stick it all back together and go rip for 10 hours before I re-check?

 

Thanks!
 
4pTw93J.jpg
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4tIHMgj.jpg

I suspect this scratching is from the casting process? Otherwise all of the other towers would be in similar condition.

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Clutch is normal.

Top of piston and head have some pretty heavy oil/carbon buildup. Check the jetting and use fresh gas.

Its always a wise idea to clean the jet circuits out on a bike thats been sitting. Especially the pilot. Some people just toss the jets and buy new as cheap insurance.

How does the side of the piston look? Typically when the machined marks are gone, you are in need of a top end.

Youre halfway to putting a piston in already, so Id just do it at this point.

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And 25$ worth of crank seals wouldn't be a bad idea either. When they sit dry for that long they can start cracking and develope leaks very soon after resurrection. Easy to change without splitting cases. There are write ups on it here.

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Oily is good. It's been running rich.

Cross hatch looks good. What's the small clean spots above the exhaust port

Probably fine to run a little. Never know about a cast piston though. I'd order one and start over.

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Oily is good. It's been running rich.

Hard to tell from the pics but I don't see any piston wash. Im not sure it has been running rich.

Black carbon build up, which it appears to have is usually a sign of lean jetting or a leak in the intake boot or crank seals.

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Hard to tell from the pics but I don't see any piston wash. Im not sure it has been running rich.

Black carbon build up, which it appears to have is usually a sign of lean jetting or a leak in the intake boot or crank seals.

Ok. It looks like it would wipe right off like oil.

What's the plug look like?

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Looks like the plating is flaking above the exhaust port.  It's common and may be ok for another 10 hrs, but a replate is probably in your future.

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Looks like the plating is flaking above the exhaust port.  It's common and may be ok for another 10 hrs, but a replate is probably in your future.

Definitely looks like it. Good eye.

If that actually IS flaking, Id personally do it now.

Millenium Technologies is commonly used by us TT nuts.

Usually a couple hundred bucks.

http://www.mt-llc.com/pricing.php

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The notched clutch basket indicates despite being stored for an unknown lenght of time, it's still seen quite some use in it's lifetime.

 

Can't see the pics, but as other have suggested,

since it's been sitting for a while give it a fresh start: new top end (pending the plating is good),

new crank seals (also lets you inspect the bottom end)

and while you're at it, measured and correct the squish band height.

 

Replace the jets (don't bother trying to clean the old ones)  float / inlet needle as well.

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Thanks to everyone who responded. I will pull the cylinder off and have a closer look at the possible flaking. Will post some better pictures with better light.
 

The notched clutch basket indicates despite being stored for an unknown lenght of time, it's still seen quite some use in it's lifetime.
 
Can't see the pics, but as other have suggested,
since it's been sitting for a while give it a fresh start: new top end (pending the plating is good),
new crank seals (also lets you inspect the bottom end)
and while you're at it, measured and correct the squish band height.
 
Replace the jets (don't bother trying to clean the old ones)  float / inlet needle as well.

 
If I can find the jets online I will grab them. LBS here are very price gougey.
 

Ok. It looks like it would wipe right off like oil.

What's the plug look like?

 

Plug was brown/black. Not too bad. I will see how easy it is to scratch the coating off the piston.
 

I would warm it up and dump the tranny oil. That and what people above said about if it's already apart, might as well throw a piston and crank seals in it.

 
Have dumped the oil already. Made the mistake of taking it apart beforehand though so I didn't warm it up.. woops. 

 

And 25$ worth of crank seals wouldn't be a bad idea either. When they sit dry for that long they can start cracking and develope leaks very soon after resurrection. Easy to change without splitting cases. There are write ups on it here.

 

These are the crank seals, right?

xy12I9q.png
 

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Welcome to the YZ club. 

 

Most all the above suggestions and observations seem great. 

 

There is no end to the amount of preventative maintenance you can do especially since a bike that has been sitting is a gamble. If you have the dough buy all sorts of seals: water pump, fork, kick, brake... rebuild the master cylinder. 

 

From what we can see of the motor I would suggest the top end and crank seals and go from there as a baseline. Oh yeah, and either hydrosonically clean or replace the jets. 

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Didn't wipe off easily.

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Much the same on the other side. Fairly clean on the intake/exhaust sides.

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Bit of lint in there from a rag I wiped some oil out with for the pics.

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Couldn't feel these marks at all.

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g2ZBQzT.jpg

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That thing ran rich, and had alot of blowby. Usually the piston will have some carbon buildup, but if it covers the entire top of the piston, it's been running like that for a while.

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Beautiful pics...can't really make out the area over the exhaust port this time...but the plating looks pretty rough all around.

You could probably get away with cross hatching and running it, but I'd replate if it were my own.

 

Piston is trash. The skirt is pretty badly worn. A healthy skirt still shows the machining marks everywhere.

What kind of premix are you using?

Interesting gloss coating on the top of it. Either lots of premix oil, rich jetting or you have a crank seal leak. A healthy piston top looks like charcoal and have some sort of burn pattern on top.

Exhibit A

YZ250_piston_top_zps48ee739a.jpg

Edited by SellYour4Stroke

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