Do i need a new top end?

[paintman922]

I have a 2002 KTM 125sx which i have recently purschased. The original owner has claimed they replaced the top end. When I have the bike at a stand-still, it has minimal power until i get going, then after the rpm's increase, it screams. Is it typical to have no low end power on a two stroke? Is there any thing i need to adjust, or is it just calling for a new top-end?

[bajadog]

My guess would be the reed valves.

The biggest giveaway is a bad idle and power loss at low revs/bogging down depending on how bad they are.

[vpolarv]

I would still get it looked at. You never know. Thats the way i do things when i buy a new bike. People will say anything, you just never know. But my 125 has good low end

[Bergey]

It's all relative to what you're used to. A 125cc 2 stroke has very little power down low, and comes on kinda like flicking a light switch at higher rpm if you're used to cars or mild 4 stroke bikes. Even my fire breathing CRF450R (a 4 stroke) is a very smooth and progressive power delivery compared to my 200XC (a 2 stroke). There is tons of power on my 450 and can be violent if you don't know what your doing, but it's very progressive and linear build up of power. My 200XC has very good low end "for a 2 stroke", but it pales in comparison to the low end of my 450, and the 200XC hits like a jack hammer when the power does come on.

If you do not have experience with 2 strokes at all it may be best to get somebody that has 2 stroke experience to take a look at it, or maybe get a compression test done.

I suspect that it's probably just you're not used to it, by the way your questions is phrased.

If the bike turns out to be fine, and you would like to mellow out the power delivery, you could look into putting on a heavier flywheel. If it does not already have one on it. That is what I plan on doing to my 200XC.