someone who knows 2 strokes

[400EXtreme]

On my ktm125sx there is no powerband at all. Could this be a stuck powervalve, need a new top end, jetting wrong?

[stalefish_132]

do a compression test. when was the last time it was rebuilt? what does the plug look like? any signs of this or was it all of a sudden?

[400EXtreme]

what am i lookin for on the plug?

[wilkin250r]

You have got an ugly road ahead of you.

Do you know why shops charge $75 an hour to do motor work? Because it requires a lot of knowledge to do it. You can't just pick up a wrench, tighten a few bolts, and everything is fixed. You need to know how your engine works, what it looks like inside, and what problems go along with what symptoms.

You have a lot to learn.

I would start with a google search on "compression testing". You may also want to learn about two stroke leak down testing.

Spark plug reading is slightly more difficult. A lot of the information on the web is about your car and worn-out plugs, it's absolutely useless for diagnosing motorcycle problems. But a search will still provide useful information.

We can't just tell you a magic bolt to tighten and fix everything on your engine. Engine work isn't difficult, but you DO need to know what you are doing if you want to do the work yourself. The only other option is to pay a shop to fix it for you.

[jakestrx400]

if its only just started, then it wont be jetting?
when did the problem develop?
try taking your carb out and cleaning all the crud out, when did you last service it?

[400EXtreme]

i pulled out the plug the threads are black but the electrode or the middle is brown. And theres been alot of oil coming out of where the silencer and header connect. Does this mean the jetting is off because it isnt burning all of the oil? Ive replaced a top end just never really touched the powervalve. So im knew to that.

[oldskoolex400]

could be your premix is to rich what are you running in it? and what ratio?

[400EXtreme]

maxima 60:1 Its not the mix because you can run anywhere from 60-40 and ive tried em all.

[dariusld]

Does the performance change when you put a new plug in? Do you get on the pipe alot or lug it around? Found this article, don't know if it applies (http://www.transworldmotocross.com/mx/how_to/article/0,13190,610643,00.html)

[400EXtreme]

yea i looked at that site and thats something i really dont want to mess around with if i dont positively know thats the problem. I just wanted to see if everyone else had this problem before i go to the dealer and get charged a fortune. The bike starts and runs great but when it comes to riding it, it bogs more than it should and there is no powerband at all. I don't know much about what happened to it because when i got it this is how it was. The bike had a fresh top end and it was still doing this. So thats why im leaning towards jetting and the powervalve.

[underpowered]

well anytime you change your oil mixture, you should change you jettin accordingly. going from 40:1 to 60:1 WILL require a jetting change in order for it to run right. to me 60:1 sounds lean on the oil, most run at 40:1, some even richer at 32:1.


the powervalve probably needs to be cleaned, they can get carbon built up on them and will stop working. but if you do not know the problem it is best to take it to a mechanic to fix it.

[400EXtreme]

is it difficult to get to and clean? Is something that u can clean when u take of f the header,pump,gas tank, cylinder head and all that stuff?