YZ250 Two Stroke Power Valve Rebuild
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- Опубликовано: 8 апр 2022
- Latest on our YZ250 build where we breakdown the process of two stroke power valve rebuild. These Yamaha two stroke have a pretty similar power valve for a lot of years and we break down he entire process from start to finish.
Links to the finished YZ story in RacerX and the steps along the way:
• Racer X Films: 2001 Ya...
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• YZ250 Tire & Wheel/Tir...
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Jay Clark/Dirt Bike TV has been around the Dirt Bike industry for thirty years and is always looking to learn and help others do so as well. Give a follow or drop an email if you have any questions or comments. Thanks for watching!
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#yamaha #yz250 #yz 
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Can you post these with no music all the way through, no fast forward, would be far superior:)
Brad always makes it look so easy!
Very interesting to see how you guys do All that awesome stuff to the yz 250..
Great video! Thanks for the tips.
what tip did he give? Help me out.
Buy that man a 30L professional ultrasonic cleaner.
Why did you speed up the video? Wanted to learn something here.
The v notch on the power valve gasket is actually supposed to be on the bottom. But yeah..
10/10 sweet video
Thank you for the tutorial , however at 9:35 the gasket is facing the wrong way, as the notch is supposed to look down not up. Not sure how much of an issue it actually is, but I figured I`d say something since the notch probably has a reason to be there.
I just put a new cylinder on my YZ250 and I double checked my manual. On page 4-19 it shows this notch "down" in the diagram.
Correct it’s down.
This comment scared me - I had paused the video when the cover came off and saw it down. Reassembled my bike then watched to rest and heard him say it went up! Thanks for clarifying via the manual
You are right, he is wrong. My cover is off, gasket stayed on the cover, Gasket notch is down, and it is for clearance for the center valve shaft bolt head.
Not too many people can do a perfect How to vid.
You make it look so easy.and l was wondering do you have to time the power valve at all on this model...
Nice job. I know we all think we're tough guys, but when you use contact cleaner like that (esp. over the years), you should put on some nitrile gloves.
Tough guys or baby sitters, take your pick.
Well, I cleaned the goop out of the hex heads, used a new allen wrench (good one too), and stripped the head out of the center power valve shaft screw. That one was too tight for the head. Had to drill the head off, drill a smaller hole and use an easy-out. Those are some soft screws. I will replace them with better ones.
Is there much friction in the powervalves, stress?
Are there seals inside the area where arm connects to the side with the screw? Above the coolant drain. My bikes just dumping bunches of oil after it sits for a while out of that cover.
Email Jay directly with any questions. Contact info in About tab.
Hi i have yz250 i saw smoke come out for the breather house it is normal?
🔥👊🔥🏍🏍🏍
I stripped the phillips head screw that goes to the keeper on the right side. Any ideas to get it out? I already tried an EZ out and it sheared. Oh lord im in over my head!
Heat is your friend.
Just wondering can you use carb cleaner or is that a bad idea!
Email Jay directly with any questions. Contact info in About tab.
Some of the material has scuffed away on my powervalve assembly. He was talking about blowby, how do you know when to replace that?
Email Jay directly with any questions. Contact info in About tab.
If it operates smoothly it is probably fine. Exhaust gas blows by the valve even when new. It is not designed to hold gases like piston rings are, and the power stroke is done as soon as the exhaust port opens up. All that brunt exhaust oil under the first cover he took off is from the exhaust gases going by that valve a bit during what is called "the blow down phase". You won't lose any power unless the valve starts hanging up.
name of the assembly music?😅
Bro my Yz 250 2t 2019 are leakin very much oil in the powervalve , i change the seals and nothing. How i can repare This? Help
email and send pictures--
The carb is jetted rich from the factory. Learn how to jet your carb, and you will get more power, and virtually no ugly oil mess. Usually, dropping the needle one notch (if your spark plug is black). leans up the middle very well, but can be a big jump. You can get little washers that go under the needle clip to go less than a full needle groove jump. Then I do wide open run to test the main jet, and put in a leaner main jet if needed until the plug is a light color brown at full throttle. (Hit the kill switch at full throttle so the plug does not darken up for a false plug reading from lower rpm running.). You plug should be a light brown color on the porcelain (and everything else dry)
Where may I obtain the cylinder hone you used ?
Email Jay. Contact info in About tab.
Looks like all you gotta do get it a "little bit clean" so you can get the "doo dads out". then take that stuff on the side off take and " important stuff" apart , pitch them in a pile, clean em up, and stick it all back together, and thats it!
I think i'll look for another video, hopefully without loud grunge music. Too fast for me.
Is it normal for oil to drip out of the power valve vent line.?
@Matthew
Yes, it's normal for the oil to drip out of the power valve hose.
@@azff Stock bikes (with carbs), are jetted rich from the factory. If he jets the carb well, he will not only gain about 2hp, but most if not all of the exhaust mess we get will be burnt in combustion and then the drips dry up. My YZ (2019) was so rich, oil coming out of the silencer ruined 2 of my jerseys, ( oil spots won't come out). Liquid droplets are fling out of the silencer. Now that is "rich". :)
@@EarthSurferUSA
I've got a 2023 Yamaha YZ250. I bought it brand new and just as your experience it was super rich out of the box. I bought a JD kit and re-jetted for my elevation (1,200 ft) and it's running great. Still getting some (not much) oil discharge out of the PV overflow hose.
Why would the power valve be hitting the piston rings? Or why would the rings be hitting the power valve?
Email Jay. Contact info in About tab.
Broken valve parts, or somebody over bored the cylinder possibly, (which would need to be re-plated and use an oversize piston), and did not modify the end of the valve.