The Secret to Power Valve Tuning on KTM, Husqvarna & GasGas 2-Strokes 

What is z dimension? The ball on top and it’s threads?

@@natm3145 The Z dimension is where the power valve flap opens perfectly when WOT, and/or Z dimension is when the power valve is perfectly adjusted. You can buy a tool from RM for about $15 to set the adjustment, but you have to have your cylinder out of the bike - a good time do do this is when you are doing a top end rebuild.

Any videos on setting this

@@TheAbbott1986 Jeff Slavens has videos on how to adjust the Z-dimension of the power valve. The exhaust port flap when fully opened where you may find the imperfection is by sight and feel only. It’s not a setting it’s a slight factory imperfection that can impede airflow.

👍 You can also use a number 2 Phillips screwdriver, like I do. You catch all four corners of that square Robertson slot.

I wish I woulda know that before I made my own tool with an angle grinder

I’ve done both in a bind but took an old 1/4” ratchet adapter and ground it down slightly to make a perfect fitting tool.

Wow another genius, it was designed for a #2 phillips screwdriver, bet you didn't see that coming eh!

This is exactly the reason and the way how I have adjusted too my PW on my Husky TC 250 2018. Red (softest) auxilliary spring adjusted flush with the cover. This way the bikes power output is more predictable. On my Husky TE 250 2015 I changed also that larger main spring for a softer one. I didn’t do this on my TC 250. So on this TE 250 2015 I had to adjust PW adjuster a little bit in with red auxilliary PW spring (softest) as the combo was too soft and PW opened too soon and this killed bottom/mid torque a bit. I got that torque lack away by just turning PW adjuster 1/2 turn in from flush.

Putting the screw flush with the case is not wise at all. You dont gain anything, you only lose bottom-end torque.

@@verttisyrjala2897 I´m sorry that I will reply one year later. My TC 250 bike has very predictable power/torque curve by setting my PW flush with the cover and using the red spring (softest most agressive). I´m a heavy rider around 100 kg (220 lbs) so I have changed my front sprocket from std 14 to 13 and rear sprocket from stock 50 to 49. It can be that this combo + other engine mods have helped but now I wan´t to try different settings. I will first turn in (clock wise) the screw 1/2 turn and test it. Then 1/8 turn more if it gets even better and helps to gain even more bottom-end and midrange torque as the exhaust port height will start to increase a bit later. You can´t say which setting works for every bike but it can be that my current setting adjusting screw flush with the cover + red PW spring will cause too soon exhaust port opening.

@@jannep6772 Thats what I was trying to say. Setting the screw flush with the case makes it open too fast and you will lose power and torque in the low/mid rpms. In my TE300 I have it 1,5 turns in from flush. I took a look at some old dyno sheets with the red spring and different screw settings. 1,5-2,5 seems good.

@@verttisyrjala2897 Thank you very much. Kiitos! I will adjust it and test it soon.

Does this apply for sumo use too?

@@marcelltomasics2487 If you set the screw flush the powervalve will open too fast and you will sacrifice bottom end torque/power. Try anything from 1,5-2,5 turns in from flush with the red spring.

Here is how you set your z dimension ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-fMSP7_jCMdk.html

Not on the carb bikes. Red spring makes the power hit over a smaller rpm range while green hits over a wider range. They all open at the same time based on whatever preload you run. Usually about 5500rpm. Red is full open i think in 2000rpms. Yellow like 2500 and green 3000. What i noticed with red is the hit happens sooner and faster but overrev suffers. I run the yellow in my 250xc as the red was harder for me to deal with traction. Also i run the kreft power dial. Nice addition.

@@TheShift1313 don't make carbed ktm gas or husq

@@fpslouis3198 the sx is still carb and my bike is a 12.

@@fpslouis3198 carbed for all MX bikes til '22' and GasGas MX is also carbed in '23'

What way would I turn it for a much more aggressive hit on a carb bike ?

125 dont have springs

@@drblik6379 wrong , on my husky tx 125 you can change the springs ,

What would cause this to happen?

When did the problem start? After making adjustments, or is it something that has just gotten worse over time? If it's from adjustments, hopefully you wrote down your starting point or how far you have moved it, so you can put it back. If it's not from adjustments, check your compression to see if the top end is wearing out. Other than that, just make sure you are up to date on your basic maintenance (air filter, spark plug, etc.) -Charles

Hey Ben, nice eye! That skid plate is coming down the pipe. Stay tuned! - Wes

@@rmatvmc oh I will!

Yes, you should be able to!

Counter clockwise.

@@rmatvmc thanks 👍

@@rmatvmc does this make the bike run leaner ?

@@robhayter484 No of course. Your carb will work as it´s been set up by jetting and needle etc. This PW adjustment only changes the rpm when the PW starts to open. Counter clockwise and it opens sooner in the rpm range and clockwise will delay the opening rpm.

@@jannep6772 cheers for the info , I’ve changed the pv spring so even better , didn’t know you could change the springs on the 125s

To meet bullshit EPA emissions

to protect their emissions claims they are tied to

From factory setting I would not go more than 1 turn in either direction or you are severely detaining performance and affecting peak. On all my bikes I’ve found 5/8-3/4 turn out gives most linear and usable power.

just in from flush is about as far out as you want to go. about one thread in.

@@cbc76am Pre 2017s flush it give or take on the 2017+ they come like 2 turns in and flush is way too far out. I learned the hard way

Preference, we run our tpi 300s all in one half to one turn in from flush. Motor is amazing there, and better with a reflash by sliber turbo.

​@@leroywilliams7210 I have a 2018 KTM 250 SX, and am trying to find where exactly the powervalve factory settings is, so I can start there. Do you know how to adjust it back to the factory setting (I bought the bike used, so it may not be on the factory setting)

Yes. RMATV sells them under OEM KTM parts

Ktm says no but there are lots of cases of people ignoring that advice. The fuel system does not have a feedback system so if you change the exhaust port and allow more air out of the engine, more can get in but the fuel doesn’t change at that specific rpm

@@JayGee6996 I run a programmable ignition on all my bikes. You can also get your stock ignition re-programmed many places that adds oil (which TPI needs in stock form). If youre going to play with the PV you should be able to do plug readings as well. All part of the fun.

@@wfodavid yeah if you’re going to do more than just pv changes you should be ok, I think ktm just cover their back to stop people playing who don’t know what they’re doing 👍

@@JayGee6996 Exactly, Spot On!

Most 2 strokes will have a power valve. I think some are electronic but most similar to this

I was thinking they got it backwards but i have a carb not tpi. On mine clockwise preloads the spring delaying the start opening of the PV. To me that is less mellow cause it hits harder :)

@@TheShift1313 so is mine. its one of the last carb models - 2018. I think maybe the key to explaining this is in where to use the word mellow. Adjuster flush with case = snappy bottom end, mellow on the top. If you add more preload (turn it in clockwise) it's mellow on the bottom but then you get the traditional mid to top end "hit".

@@TheShift1313 It hits harder because you’re delaying it, but by doing so you’re losing some mid power and often if delayed too far the peak is actually never hit. JD did some awesome tests on the dyno and you can clearly see if too far in either direction it affects the whole range.

@@leroywilliams7210 i think we are saying the same thing :) preloading the spring delays the pv open rpm. It doesnt necessarily change peak power unless like you said you go a bit to far. The main thing we do is change the starting rpm and ending rpm for the PV as well as the "ramp" it opens. I think the mellow term is whats throwing me off. Someone mentioned the mellow setting is the red spring and i guess if you just idle around maybe.

@@TheShift1313 Yes I find people think it has more power IN because there is less power down low and then a sharp “hit”! I like my PV out a little to give me More Power Earlier and more linear power into the same hit and up.