To bore, or not to bore...that is the question.

mxracer_0141

mxracer_0141

PR Member
so ive got a 2005 yz125 that im tryin to get some more horses outta to keep up with these 250 four and two strokes this season. the first option i stumbled upon was the 144 kit. i have never bored any of my bikes (and have never blown a single bike up nor had any problems with any of my bikes) so i honestly dont know how reliable this process is. any input on it? my second option is porting and polishing it, putting a v force 3 reed cage in it and changing the gearing on it. how much would that help me? ive already got a fmf sst with a titanium 2 silencer on it. im just trying to get a little more power outta my little 125 to keep up a little more instead of spending 6 grand on a ktm150 or buy a 250 2 stroke that will ride me more than i will ride it. any input on this would help me out alot!
 
Have a 09.. stock bore with vforce reeds and doma pipe/silencer with 2 teeth added to rear sprocket and one step richer from stock on jetting and the bike runs very good with this set up. had a 06 139yz and a 08 144sx and have to say there is not that much between them all. just a blast to ride!!!!
 
mxracer_0141 said:
so ive got a 2005 yz125 that im tryin to get some more horses outta to keep up with these 250 four and two strokes this season. the first option i stumbled upon was the 144 kit. i have never bored any of my bikes (and have never blown a single bike up nor had any problems with any of my bikes) so i honestly dont know how reliable this process is. any input on it? my second option is porting and polishing it, putting a v force 3 reed cage in it and changing the gearing on it. how much would that help me? ive already got a fmf sst with a titanium 2 silencer on it. im just trying to get a little more power outta my little 125 to keep up a little more instead of spending 6 grand on a ktm150 or buy a 250 2 stroke that will ride me more than i will ride it. any input on this would help me out alot!
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Google Eric Gorr, 640 bucks for the bore, port and polish, set up to the power band you want, piston, rings, cir-clips, wrist pin, bearing and gaskets. He is arguably the best around for two stokes?
 
yeah i looked him up already and was looking into that. 640 bucks for all that, plus labor? or 640 bucks and its ready to go?
 
Yeah send if to gorr. I have the same bike as you with same pipe but a 144 and love it. My crank went out but I think is was going bad when I bought it.

Still put the vforce on it and 13 50 gearing. It still won't be as fast as a 250f. But not far off
 
Trust me the 144 kit makes a HUGE difference. And yes it will keep up with a 250 4stk. I have the athena 144 kit and it rips.
 
i have both bikes 144 and 250f stock and yeah the 144 can keep up but there is no doubt the four stroke is faster. No by that much though.
 
Andrew if it wasnt a yamaha and it was a KTM 125 it would keep on STOCK! lol. but no i honestly think the 125s are pretty darn close stock to a 250f? with the 144 kit it should be faster, but i been gone a while so idk anymore.
 
What about a small stroker kit? Maybe more reliable in the long run, or not...

What would you guys say is more reliable bore or stroking?

My buddy slapped an athena kit on his kx 125 and when he fired it up that thing just sounded mean as hell. Can't go wrong with the Athena kit...
 
Honestly, it'd probably be easier to sell it to someone with a kid that needs a 125 and buy a 250 2 stroke, since your allowed to run in the same class its like cheating but no really and its kinda like a 450 with more speed and sounds alot cooler when your bouncing around a corner 3rd gear pinned on the rev limiter. I'd just sell the bike, and take the money you were gonna invest in amping up the motor which isnt always a safe bet, and buying a newer 250 2 stroke and getting some suspension and brake work done.
 
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