2 Stroke Help Needed!!!

[Antnee77]

On a two stroke bike, is there a screw on the engine that can adjust the power output? My friend is looking into a KTM 250EXC but wants to tone it down a little for his trail riding. We called the local KTM dealer and the parts guy said that there is a screw on the engine that can adjust it from "a *****cat to a flame-breathing dragon". I thought it was the fuel-air mixture screw but it's not. Anyone know what this guy is talking about???

[SHOCKER]

:huh never heard of such thing, the only thing i have heard is on thumb throttles, ya know on thumb throttles ya can screw that screw in so ya kid wont go past half throttle or 1/4 throttle or whatever, but thats totally diferent,

[K_Banger125]

Originally posted by Antnee77
On a two stroke bike, is there a screw on the engine that can adjust the power output? My friend is looking into a KTM 250EXC but wants to tone it down a little for his trail riding. We called the local KTM dealer and the parts guy said that there is a screw on the engine that can adjust it from "a *****cat to a flame-breathing dragon". I thought it was the fuel-air mixture screw but it's not. Anyone know what this guy is talking about???

:huh i don't know what that guys talkin about...my bike doesn't have one thats for sure i have a fuel air one and a idle screw thats it and those are on the carb

[LTandRaptorider]

They might be talking about adjusting the spring tension on the power valve? :confused:

[MotoX3]

Originally posted by LTandRaptorider
They might be talking about adjusting the spring tension on the power valve? :confused: thats what i was thinking:macho

[wilkin250r]

Originally posted by LTandRaptorider
They might be talking about adjusting the spring tension on the power valve? :confused:

ha. I bet that would work, too. Crank that bad boy down so the powervalve never opens. I bet you cut the horsepower nearly in half.

[MotoX3]

alright hold on now wilkin you got my attention...im a total idiot when it comes to engines...by adjusting the power valve you can gain hp correct?....is it an all around power or in certain areas?does it affect your engine at all(reliability,starting ect)?...and does it come from the factory adjusted for full power or what?...thanks for any info:macho

[Antnee77]

Where do you adjust the spring on the power valve?

[K_Banger125]

Originally posted by wilkin250r
ha. I bet that would work, too. Crank that bad boy down so the powervalve never opens. I bet you cut the horsepower nearly in half.
if you did that on a 2 stroke dirtbike you would never hit powerband and would be fouling plugs out the *****

[LTandRaptorider]

Originally posted by wilkin250r
ha. I bet that would work, too. Crank that bad boy down so the powervalve never opens. I bet you cut the horsepower nearly in half.

You can make SLIGHT adjustments to it to have the valve open at a different rpm range. ;)

[Antnee77]

What should I do to make this thing less high-strung? Put on a sprocket up front with less teeth?

[LTandRaptorider]

Originally posted by Antnee77
What should I do to make this thing less high-strung? Put on a sprocket up front with less teeth?

bigger sprocket in front, or smaller in rear will take away from bottom end power, give more top end speed. smaller in front, or larger sprocket in the rear will give you more power on the bottom.

[lil400exman]

well you can adjust it to make it more smooth now antee you can tighten down on the PV screw so it wont open as much but then u could get carbon build up........... the PV tension screw basically helps keep in in tune not adjust power.;) on my YZ i reset every month and it helped keep it real tight and responsive:devil:

[flyin#5]

there is no such screw, and ajusting the powervalve wouldnt be the smartest thing to do. port timing is critical on a 2 stroke, if your holding in exhaust when it should be going out the pipe you will not have a running bike for long. if you dont know what your doing, dont do it. your friend doesnt need to tone the bike down, he needs to tone down his riding. dont rev it out all the way, and only hit the powerband when shifting. its not that hard...

[Antnee77]

He can tone down his riding, but it still accelerates pretty rediculously. I don't want to see him ride off the trail. Would a smaller sprocket up front even make a noticable difference on bottom end power?

[bradley300]

a smaller sprocket on the front will just make it accelerate even faster. best thing to do is try to find an exhaust w/ very low rpm hp. its still gonna accel real quick, but at least you wont have to keep it wide open all the time

[Antnee77]

Couldn't he put a governor in the carb to limit the throttle movement or something? The same guy at the local dealer also said that you could put a screw in the carb to stop the throttle cable from moving to much.

[TGW_400ex]

why the h*** did he buy a 250 then:huh tell him to sell it for a 125;)

[Antnee77]

Cuz he got an awesome deal on it. He's gonna keep it and get used to the power. Thanks for the help anyways guys.

[LTandRaptorider]

To summarize... don't screw with the power valve setting, usually the factory setting is best... there is no magical screw on the engine to give you more power... make sure the bike is jetted properly, and in a good state of tune... ride it easy until he gets used to having more power than the 125. Smaller sprocket in front=more low-end... bigger sprocket in front=less low end, more top end. opposite is true when changing the rear sprocket. Have fun! :)

[Antnee77]

Thanks for the help guys.

He bought the bike yesterday and when we brought it home, it started to pour. So today, he asked me to take it around the block. I got on it, kicked it over, and gave it a tiny bit and let of the clutch slowly. The bike stalls. Try it again. Bike stalls. I tried it one more time before getting really frustrated. So the 4th attempt, I said "I got to give a little more gas". So, without thinking, I revved like 1/4 throttle and let off the clutch. Not being used to the hydraullic clutch and it's small amount of movement, I popped it and the bike jerked foward. This jerk forward caused me to fall towards the back of the seat and to gun it. The bike hit the powerband and flew up in the air. I went off the back and landed hard on my @$$. The bike went like 10 ft into the street. I almost $hit my pants!!! Kind of a stupid mistake riding a 250 as the first two-stroke I've ever ridden. This bike is FAST!!!

(Don't laugh....if I didn't have a helmet on I might not have had a chance to share this stupid story with you guys!)