kx250 vs ktm125

[GRARA]

Back again....recently bought my son a 2004 Ktm 125 ( sorry)...on take off and top end it destroys my 94 KX 250!!  is it just my bike is older or does it sound like my bike is failling in some way? It's recently had replated barrel and piston etc plus new power valves....

[KXDINO]

this stuff happens all the time , i have seen 125 holeshot against 450 only cause the 125 pilot holds it on longer and brakes later but that aside the old 94 250 should put around 42 to 43 hp at the rear wheel and the ktm 125 04 around 35 mark give or take one or two , are both bikes std on the kx is the powervalve timed correctly is the crank seals good , are the reeds in good order , what gearing you running , clutch not slipping , you need to check this stuff out and more even the jetting is a must as well , as i remember the 94 did not have a lot of power high up in the revs range , i had a new 95 at the time and they fell short on over revs as well but were quick off the line and tight tracks , i remember drag racing to cr500 of the time and they only past when clicking top gear.

[GRARA]

Thanks for the reply, his 125 has been tuned but not sure to the extent as we lost the list of mods!!  My crank seals are not the best ( bike smokes like a dragon)  but other than that every thing is in order... My KX still lifts in 3rd,  but your right about top end power plus it's only 5 speed not sure what the gearing is just now.

[treedodgingfool]

Bad crank seals and sucking tranny fluid is definitely an issue (act's like overly fat jetting on tranny side that won't clear out), on top of any other possible issues that effect performance (reeds that aren't sealing right, tension lost or chipped, exhaust sealed up correctly & not dribbling at head or silencer joint or collapsed/blown out packing in silencer, PV's, etc. and lastly jetting since that needs to be addressed when everything else is spot on).

[badmoosecycles]

I had a slipping clutch on my kx250 -98.
Now that i replaced the basket, all plates and springs the only thing slipping is the rear wheel.
A totally different bike now, moves like a rocket.

[treedodgingfool]

Another note to add is drag racing dirtbikes usually doesn't always end with the results we'd expect anyway, it usually proves nothing.  I've seen a XR250R out run a TRX250R, YZ250 & YZ125. I've out dragged (during a race) on my '04 KX250 when it was stock displacement against a XCW450.