The power valve shaft, #11 in the factory service manual, should have the retaining clip, #8, installed as soon as the shaft is put in. This will locate it precisely for the rest of the build. The fitment of the barrels was giving you issues as the shaft was sliding left and right which you kinda figured out at the end of the video. Also the crecent cut of the power valve shaft at the retainer should be to the upper right as you are looking at the retainer after it is installed. This will keep the cut out away as it is motion. Great video btw, really helped me!
U the man Dave. Thx lost track of the order of washers going back in I’m just happy I didn’t break anything and that I didn’t need to re Nickel sil plate my cylinder.
Thank you so much. This video was super helpful. I am in the middle of rebuilding my YZ250 from the ground up. During the tear down, I broke the piece you mentioned that commonly breaks on this type of power valve. So I had to order a new one. They are not cheap...:-) Thanks for the tip on having the sub ports completely closed when tightening the 3 mm screws. This video was super helpful. Thanks again.
So after it’s put back together, when you pull the valve open is it supposed to spring back closed On it’s own? Or does it not have any spring retention?
I noticed you said it doesn't matter which side the drums go in. Wouldn't be ideal to keep previously mated surfaces together unless you are replacing as a whole? Could you rotate the drums and use the the top surface where the forks would make less contact as fresh surface or are the drums directional, i.e have a top and bottom- clearly they slide into the cylinder one way. I'd imagine most the wear occurs at the fork pivot point, the fork its self and the pin the fork engages with in the groove of the drum. Awesome vid thanks
That powervalve is broken... the stopper in the centervalve is broken and that is not something you ride with! Replace the center-valve with the one used in 99 to 01 bikes. Its a beefier valve that doesnt break like the 03 onwards does.
Amazing someone could think this up and make it ........Why lock tite and to the job if the one part is broken , you'll just have to take it apart when the new part comes in?
This was very helpful and led to me discovering that my transition thru no power valve actuation and full activation has a slight studder that seems like 1-2 rpm of hesitancy - do you have any idea how i can eliminate that hesitancy as it kicks in as i am hitting a jump face and is very alarming?
When you're using the pliers to open/close the powervalve.. is that under spring tension or could you very easily do that with your fingers as well? hopefully your answer solves the issues with my bike. Haha
Question. I have a yz250 new top and bottom rebuild. Power valve opens main valve but not the subs. If I turn by hand they all open, main first then subs. The linkage lifts enough to open the main when revving but stops too soon. Stock everything except fmf silencer. Power is great on the bottom and mid. Top feels like a 125cc
I have a major question.. the ring that's used at the end of the long power valve rod.. is that seated to the 1st wider groove or the smaller deeper groove .
Sorry if you mentioned in the video, Dave (didn't end up watching it all). Is this something that can be done with the engine still in the bike? I'm guessing the piston and everything can stay together while removing this?
its extremely difficult. stock cylinder will have phillips screws holding the cover on the PV, so you'd need needle nose vice grips to remove them in most cases (the PV cover sits too close to the frame/rads to get a screwdriver in there). then its a matter of "can I even see wtf I am doing?" Sure it can be done and has been done. but in an extra 15 mins you can have your cylinder off and not worry about the hassle of working in a confined space
The power valve shaft, #11 in the factory service manual, should have the retaining clip, #8, installed as soon as the shaft is put in. This will locate it precisely for the rest of the build. The fitment of the barrels was giving you issues as the shaft was sliding left and right which you kinda figured out at the end of the video. Also the crecent cut of the power valve shaft at the retainer should be to the upper right as you are looking at the retainer after it is installed. This will keep the cut out away as it is motion.
Great video btw, really helped me!
I watched the whole video to find this out
U the man Dave. Thx lost track of the order of washers going back in I’m just happy I didn’t break anything and that I didn’t need to re Nickel sil plate my cylinder.
Thank you so much. This video was super helpful. I am in the middle of rebuilding my YZ250 from the ground up. During the tear down, I broke the piece you mentioned that commonly breaks on this type of power valve. So I had to order a new one. They are not cheap...:-) Thanks for the tip on having the sub ports completely closed when tightening the 3 mm screws. This video was super helpful.
Thanks again.
Very helpful thank you. I am just beginning a top end rebuild and hadn't realised the powervalve on the 250 is different from the 125.
You know I've been doing this for a very long time absolutely one of the best videos I've seen out there good one on you mate
So after it’s put back together, when you pull the valve open is it supposed to spring back closed On it’s own? Or does it not have any spring retention?
Thanks Dave, very informative and interesting! Great work!
I noticed you said it doesn't matter which side the drums go in. Wouldn't be ideal to keep previously mated surfaces together unless you are replacing as a whole? Could you rotate the drums and use the the top surface where the forks would make less contact as fresh surface or are the drums directional, i.e have a top and bottom- clearly they slide into the cylinder one way. I'd imagine most the wear occurs at the fork pivot point, the fork its self and the pin the fork engages with in the groove of the drum. Awesome vid thanks
Now that's proper tutorial! Thank you.
Very interesting.
I thought it was cylindrical (Looking in when the exhausts are off).
It always helps to know what shape things are.
Aside from the incorrect camera orientation, great video.
mega pomocny filmik przy składaniu zaworu wydechowego yz 250...dzięki kolego ... super interesujący materiał.
Fantastic video. All the negative people leaving their 2 cents are ridiculous. Great job man.
Your bench seems to be missing the oil seal. Thanks for the video.
Thanks good vid
That powervalve is broken... the stopper in the centervalve is broken and that is not something you ride with!
Replace the center-valve with the one used in 99 to 01 bikes. Its a beefier valve that doesnt break like the 03 onwards does.
Love the step by step thank you
Amazing someone could think this up and make it ........Why lock tite and to the job if the one part is broken , you'll just have to take it apart when the new part comes in?
Excellent job
This was very helpful and led to me discovering that my transition thru no power valve actuation and full activation has a slight studder that seems like 1-2 rpm of hesitancy - do you have any idea how i can eliminate that hesitancy as it kicks in as i am hitting a jump face and is very alarming?
Such a helpful informative video, merry Christmas to you and your family! Thank you.
Great video! Ty!
Great Video. Thank you.
At what rpm point does the valve start to open.👍🥃🇦🇺
Would this cause wide open throttle if broken?
When you're using the pliers to open/close the powervalve.. is that under spring tension or could you very easily do that with your fingers as well?
hopefully your answer solves the issues with my bike. Haha
Justin Pelkey It's not under spring pressure but kinda hard to do with your fingers. Plyers make it easy.
Question. I have a yz250 new top and bottom rebuild. Power valve opens main valve but not the subs. If I turn by hand they all open, main first then subs. The linkage lifts enough to open the main when revving but stops too soon. Stock everything except fmf silencer. Power is great on the bottom and mid. Top feels like a 125cc
Well explained thank you
The 2 side cylinder don’t even move on mine
No Bueno
I have a major question.. the ring that's used at the end of the long power valve rod.. is that seated to the 1st wider groove or the smaller deeper groove .
I thought 2 strokes didn’t have valves don’t bash me because I’m new to dirt bikes
itzKert Music this ain't the kind of valve your thinking. This valve is more like the ones found in automatic transmissions.
Edward Duran oooo thanks for letting me know very useful information 🙏💯
That's for exhaust
Not not a piston valve like on a four stroke
JIS screw heads, not Phillips mate.
Sorry if you mentioned in the video, Dave (didn't end up watching it all). Is this something that can be done with the engine still in the bike? I'm guessing the piston and everything can stay together while removing this?
its extremely difficult. stock cylinder will have phillips screws holding the cover on the PV, so you'd need needle nose vice grips to remove them in most cases (the PV cover sits too close to the frame/rads to get a screwdriver in there). then its a matter of "can I even see wtf I am doing?" Sure it can be done and has been done. but in an extra 15 mins you can have your cylinder off and not worry about the hassle of working in a confined space
This was also my question. Thank you sir. Great video. Much appreciated
Good video
excellent..thank you
Hi just a quick 1. The seal that u mention at 17:54 needs replacing on my bike, do i have to remove the pv shaft to replace it? I have a 2007 yz250
yes, you need to remove the shaft to replace that seal
Ciao funziona con la testa della valvola rotta ?
you should not be having to do that if you payed a good company to redo you top end
I found the same piece broken on mine ... are you able to run it with the broken stopper ? What does it do exactly
What did you film this with a toaster?
Do I have to remove the power valve to remove cylinder head?
Edward Duran no just a litle arm on the left side
@@thibo2107 cylinder head only head bolts.....and stay....cylinder ...8mm bolt in arm.