2003 cr125 cylinder ???

78TA

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#1
2003 cr125 cylinder interchange with any other years???

Is there any other years that will fit? Can you go 144 with the 03 cylinder.

I tried searching, but came up empty handed.
 
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#2
i have never seen a cr larger than a 144 i am sure it is cylinder only if i were you i would do 2mm on the crank and 2mm on the cylinder.
 

78TA

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#3
i should refrase question.

what year cylinders will interchange with an 03 cr125?

I ask because I would like to get a spare cylinder, possibly for a big bore/port job.

next question, how big of a bore can the 03 cylinder take? Is ther any other years of cylinders that will interchange that are better to make a big bore out of?


thanks
 
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#4
78TA said:
... I ask because I would like to get a spare cylinder, possibly for a big bore/port job.

thanks
Isn't that simple. The 144 will require other mods than just a bored cylinded and larger piston assy. Your power valve assemblies will differ as well. So, to interchange I suggest you communicate with Forward Motion, chances are Eric has a complete cylinder up 144... be prepared to write a nice check and you may need some case mods as well.
 

78TA

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#5
I was mainly interested in knowing if there are any other years of cylinders that are a direct swap on the 03 cr125?

And as a second question, how big can the 03 cylinder go, and if there is any other year cylinders that are a direct swap, that are a better candidate for a big bore?


Sorry if it is confusing,


thanks
 

Pete Payne

MX-Tech Suspension Agent
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#6
I am pretty sure on 02 will interchange with the 03 .
Best bet is a 3mm overbore . I have built many of them in my shop . Also have built quite a few CR 144's ( yes ther is room for it ) . The problem with the 144 bore is the way the Honda exh. port is designed . To make the 144 bore work out and not make the exh port extreamly huge we have to offset the cylinder bore to the rear . Then the head gaskets like to blow because of the placement of the rear cylinder stud.
So go 3mm and it will work good .
 
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#7
thanks pete!

anybody else know what year cylinders will interchange with the 03?
 

Eric Gorr

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#8
The 03 has a differnt base stud location and the 2003-07 are the same. I do a 144 kit on the 2005-07 so if you get a used top end it will fit on the 2003 and newer CRs. Pete is right in that you can only bore the cylinder to 139cc 57mm but if you buy a Hot Rod crank, you can stroke it 4mm to make a 125 AMA maximum oversize 153.
 
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#9
Eric, what else do I need to get besides an 05-07 cylinder to switch to newer top end (power valves, head ect)???

Is just the stock 05-07 top end an upgrade over the 03? and would it be worth the money, or is it only worth the money if you wanna do the big bore?

Is the 03 cylinder a good candidate for porting? Are the 05-07 better?

Is the 144 kit for 05-07 all bore or is that stroked also?


Sorry for all the questions, I ask all these questions because I'm lookin for more power, and I would like to know what are my options and best bang for the buck. I would like more power mostly in the mid and top end without losing so mutch down low that it can't be trail ridden.

Thanks in advance
Travis
 

Pete Payne

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#10
Eric is right , the base stud pattern is didfferent from 02 to 03 . (Eric , you the man !)

78TA ,
to get to 144 cc's you would need to do the 3mm overbore along with a stroke increase of 2mm for a total stroke of 56.5mm
actual displacement would then be 144.174cc's
 
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#11
Any body know anything about the 05-07 top end swap for my 03? powervalve set up is completely different.


Thanks for the replies