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Author Topic: engine differences between 2001 and 2005 yz250  (Read 5514 times)

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Offline coblefutch

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engine differences between 2001 and 2005 yz250
« on: January 04, 2014, 03:16:11 PM »
I guess I cracked my case on my 05, I found a good condition case on ebay but it's an 01 and when you look up the oem part numbers they are different.
Will it fit, what changed, I don't think it has to do with the switch to AL frame as the 04 cases were for the steel frame yet have the same pn as the 05 aluminium frame model??
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Coop

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engine differences between 2001 and 2005 yz250
« Reply #1 on: January 04, 2014, 05:52:49 PM »
I have no idea how accurate it is, but according to this parts site, 2002 on will fit your bike.

http://www.2wheelpros.com/oem-parts/yamaha-crankcase-1-5nx-15111-01-yx-part.html
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
- Mike - Don't take life so seriously, nobody gets out alive.

Offline Dirtsaw

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engine differences between 2001 and 2005 yz250
« Reply #2 on: January 04, 2014, 06:38:40 PM »
Pretty sure the 02 fwd engine is a different design from previous motors.  I think this is when the cylinder was rotated to be more vertical and the power valve design changed.  I have an 02, I think I remember it being a new design for that yr...  If it's a diff part number it probably won't work..
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline coblefutch

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engine differences between 2001 and 2005 yz250
« Reply #3 on: January 04, 2014, 07:06:16 PM »

Damn, that's to bad cause it was a good price.. I figured as much though.
Thanks for the response...
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline mj4trax

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engine differences between 2001 and 2005 yz250
« Reply #4 on: January 05, 2014, 02:59:34 PM »
my understanding is that the '99+ motors are all the same, with some slight changes being made to the cylinder porting in 2000. 

Interesting to know that the p/n of the cases changed though. 

My 2001 yz250 has a quite vertical cylinder. 
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
2003 RM250
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2001 yz125
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1989 trx250R

Offline Dirtsaw

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engine differences between 2001 and 2005 yz250
« Reply #5 on: January 05, 2014, 07:12:23 PM »
Maybe it is in 99 when the motor changed.  Actually I think I got confused.  02 is when the airbox changed to the current design...  I still wouldn't trust it with a adiff part #..

« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline mj4trax

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engine differences between 2001 and 2005 yz250
« Reply #6 on: January 05, 2014, 10:18:55 PM »
Yes, '02 was the last change to the airbox and to the plastics.  For that reason alone, I really wish my yz was an '02 instead of an '01.

My guess is that whatever difference there is with the cases wouldn't make a difference on the bike, but can't help to validate. 

If you're finding them cheap enough, it's likely worth the risk as the worst case would be you re-selling the cases for a profit  ;-) 
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
2003 RM250
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2001 yz125
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1989 trx250R

Offline Paul P

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engine differences between 2001 and 2005 yz250
« Reply #7 on: January 06, 2014, 03:44:27 AM »
I recently rebuilt a crank for a friend with an 01 and 02 YZ 250. I compared the two cranks side by side. The crankshaft wheels are 1mm larger in diameter on the 02, so you won't be able to swap out cranks or cases, unless you machine the cases about 1/2 mm larger to accept the slightly bigger crank. Not much else looked different between the two motors internally. I would not use the 01 crank in the 02 case, as you would loose too much base compression, and turn it into a slug.
   I wasn't able to see if the motors would swap into either frame.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline jar944

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engine differences between 2001 and 2005 yz250
« Reply #8 on: January 06, 2014, 01:19:37 PM »
99-14 cases are the same

Except the 99-01 use a smaller dia swingarm pivot. You would need to bore the case insert to match the 02+

01/02 crankshafts are identical 5MW-11400-00-00
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Paul P

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engine differences between 2001 and 2005 yz250
« Reply #9 on: January 08, 2014, 12:19:51 AM »
The crank wheels were different on the YZ's I worked on. Maybe the owner has 2000 and 2001 models and doesn't know it.
      It could be as easy as getting the correct bushings for the swingarm pivot like on the Honda CR's to swap motors into a later chassis..
That's good to know then, that it is the casting internals of the motor that are slightly different. You could probably find a 99 motor or bike cheap, and have a spare motor ready to go for different types of riding/racing.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »