03 CR 125 mods

Jman271

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#1
Anyone out there have any good porting mods for the 03 CR 125??? Does it still suffer from same problems as 02??? How was the squish? I plan on tearing into one this week and going through it w/ TSR. Just wondering if there were any problem areas I should look for as far as higher trans low exhuast durations. I know the 04 has a lower comp ratio,,,,,anyone? Marcus, Steve125???
 

marcusgunby

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#2
LOL dont try its a doomed project:) steve will tell you it can be improved but so can anything given enough time and money-main problem is the ports are huge.Steve will give you alot of usefull info im sure.
 

bclapham

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#3
i hear a for sale sign is a good bolt on mod for the cr125 :p sorry, i couldnt resist- i am just glad marcus's RM makes good power so he cant moan at me for convincing him to buy it, LOL
 

Jman271

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#4
Ouch, is it that bad? Haven't ridden one, but heard they are down on power,,,
 

steve125

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#6
Jman

I think you'll find the cylinder's timing spec's out around 12-12,500 rpm. It's a mess really. It's best to tune this motor for mid to top and dont worry about the low end. The std carby is jetted close and leave the reeds and reed valve alone except for closing the reeds stops to 8mm open.

The best pipe for mid to top is the DEP!!! it rocks :thumb:  and the PC for a bit more than stock.

The cylinder is the main problem, large transfers and a real high ex-port. Funny though if you lower the cylinder to much for more low you won't get it, but will get less top.

So .010 off the base, race fuel, match the transfers, a good piston thats not stock, wiseco SRS Vertex all fine, blend the ex-valve to the port roof when open, 380-400 main, DEP pipe with PC shorty, 1-2 teeth up in the rear.

With all that it will be fast but not too easy to ride, but much better than stock.

have fun :scream: :)
 

Jman271

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#7
12,500??? Wow, that seems high. Seems more like peak RPM should be somewhere in the 11k+ range to me. Thanks for the tips, I will check it out and let you know how I make out. Also, when you said match trans, are they staggered? Or are they all at same mm now but just need massaging? Thanks again, see ya!!!
 

steve125

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#8
I would just pick the highest one left or right and then match both to that spec.

 let me know what peak RPM numbers you come up with.