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So I am rebuilding my 2001 yz 250. I really only woods ride it l. I have an 11oz fly wheel already but I would love the bottom end power that the porting on a xc bike can offer. so I was wondering if a yz250x head would fit on it!? Is there any clearance issues? Has anyone ever done this? The cylinder gaskets looks very similar so I'm wondering if there would be any issues with it. Thanks in advance!! 

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I imagine the head will fit fine without any clearance/mechanical issues but i do not know how well it will work.  You would probably be better off just sending your 01 head out for work, send it to reputable machinist who knows what they are doing with the yz250's and get them to set it up for what you want.  

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The x head will fit on the yz. It's the same engine but the compression on a x is lower.

You can change the OEM yz head with a good squish clearance and the right compression for riding woods.

Also changing the gouvernor spring could be a good and cheap way to change the power delivery

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42 minutes ago, subxero said:

I imagine the head will fit fine without any clearance/mechanical issues but i do not know how well it will work.  You would probably be better off just sending your 01 head out for work, send it to reputable machinist who knows what they are doing with the yz250's and get them to set it up for what you want.  

Would that not be more expensive than just buy a new head with the work already done to it? The new heads are roughly $500

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1 minute ago, KMcL said:

Would that not be more expensive than just buy a new head with the work already done to it? The new heads are roughly $500

yes and no.

A new head is just cut to more or less a baseline setting so to speak.  Something that should work decent just about anywhere.  If you send the head out, it shouldn't cost much more and you can get the head cut specifically for your elevation and riding preferences among other things.

 

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1 hour ago, KMcL said:

So I am rebuilding my 2001 yz 250. I really only woods ride it l. I have an 11oz fly wheel already but I would love the bottom end power that the porting on a xc bike can offer. so I was wondering if a yz250x head would fit on it!? Is there any clearance issues? Has anyone ever done this? The cylinder gaskets looks very similar so I'm wondering if there would be any issues with it. Thanks in advance!! 

The X has a different ported jug, center PV, and pipe. The head is a 5MW, with a different squish and is actually designated as a BF1. Gaskets and O-rings are the same. Fitment no problem. 

Squish needs to be corrected for woods anyway. 

To make the YZ, a YZX without 3-5 WR gears, it would be the governor mod, jug, head, PV, and pipe. If you really want to change the clutch feel, bolts, washers, springs on the clutch basket. Might be another thing I am missing.

I have a complete YZX top end I traded with a member that is going off to plate shop as soon as my Vertex A piston arrives, and then it's 4 weeks out from new re-plate. Still need to figure other things out, but I got the stock head, and RK Tech with it, but the center PV was broken un be known to trade. 

 

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51 minutes ago, 2 STROKE YZ DOC said:

The X has a different ported jug, center PV, and pipe. The head is a 5MW, with a different squish and is actually designated as a BF1. Gaskets and O-rings are the same. Fitment no problem. 

Squish needs to be corrected for woods anyway. 

To make the YZ, a YZX without 3-5 WR gears, it would be the governor mod, jug, head, PV, and pipe. If you really want to change the clutch feel, bolts, washers, springs on the clutch basket. Might be another thing I am missing.

I have a complete YZX top end I traded with a member that is going off to plate shop as soon as my Vertex A piston arrives, and then it's 4 weeks out from new re-plate. Still need to figure other things out, but I got the stock head, and RK Tech with it, but the center PV was broken un be known to trade. 

 

What is 5MW? From what I've been reading the squish of these heads it's very lax and people go through alot of work to make it tighter. Could I leave the squish the same as a yz head and just have the same compression? 

I have also bought new gears for it that will be installed as well. And what is this governor mod you speak of? 

 

All in all though, with all the little tweaks aside would everyone agree it would a good modification to make? 

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What is 5MW? From what I've been reading the squish of these heads it's very lax and people go through alot of work to make it tighter. Could I leave the squish the same as a yz head and just have the same compression? 



I have also bought new gears for it that will be installed as well. And what is this governor mod you speak of? 



 



All in all though, with all the little tweaks aside would everyone agree it would a good modification to make? 
Having your squish corrected is a must do mod imo. Good squish makes them so much more tolerant of temp and elevation changes, way easier to jet.
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So I am rebuilding my 2001 yz 250. I really only woods ride it l. I have an 11oz fly wheel already but I would love the bottom end power that the porting on a xc bike can offer.

so I was wondering if a yz250x head would fit on it!?.....YES

Is there any clearance issues?....NO

Has anyone ever done this?....YES

The cylinder gaskets looks very similar so I'm wondering if there would be any issues with it.....NONE

Thanks in advance!! 

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