2019 yz power valve

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11/18/2018 8:01 PM

Has anyone removed the power valve system on yz85/65 ? How to remove roller Photoshaft . Any ideas ? Cheers

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11/18/2018 8:47 PM

Looks like the 125's should have a allen head bolt in the center. Loosen it and then you can slide out the rod. Then the rest should be pretty easy to figure out. Just make sure you clean out the bolt head of excess oil first before loosening it with the oil it can make it easy to strip.

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11/18/2018 8:59 PM

Dude! What oil and ratio are you running?

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11/18/2018 9:33 PM

Underground wrote:

Dude! What oil and ratio are you running?

That’s what I was thinking.

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11/18/2018 9:35 PM

50:50 w00t

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11/18/2018 9:58 PM

SmokinJoe439 wrote:

Looks like the 125's should have a allen head bolt in the center. Loosen it and then you can slide out the rod. Then the rest should be pretty easy to figure out. Just make sure you clean out the bolt head of excess oil first before loosening it with the oil it can make it easy to strip.

Hey bud, that right has one Allen key bolt, removed that , but it's still in there tight, I'm reluctto yank on it to hard at this stage, one would think it should remove with little effort ..

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11/18/2018 10:00 PM

Underground wrote:

Dude! What oil and ratio are you running?

Run 40:1 Belray 50:50 Avgas and 98... I've seen other bikes with a lot of oil residue that running 50:1

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11/19/2018 2:04 AM

Underground wrote:

Dude! What oil and ratio are you running?

Kiwikemo wrote:

Run 40:1 Belray 50:50 Avgas and 98... I've seen other bikes with a lot of oil residue that running 50:1

Jetting is obviously rich then

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11/19/2018 8:22 AM

You have to remove the center stopper plate Allen bolt first like i said or nothing is coming out without breaking something.

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11/19/2018 12:27 PM

Underground wrote:

Dude! What oil and ratio are you running?

Kiwikemo wrote:

Run 40:1 Belray 50:50 Avgas and 98... I've seen other bikes with a lot of oil residue that running 50:1

Underground wrote:

Jetting is obviously rich then

Too much oil in the PV assembly has very little to do with air/fuel ratio, lol.........

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11/19/2018 5:37 PM

Oil in PV cover is a GOOD thing...

The parts need it to function - and if have very little it cooks and leaves deposits stopping the valve.

It has a self regulating oil height. The powervalve cover has a hose attached and once the level gets high enough it drains out - yamaha could lower this height - but why!?
It would be like running your 4 stroke engine with no oil - who would do that!?

You remove the little allen - then the shaft is held in place with a plate on the side of the cylinder that a screw holds. remove that screw than pull the shaft out.

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11/19/2018 5:52 PM

Hi thanks

I totally agree with you on the Oil residue.. managed to remove shaft.. no screw ( older but there is a locking pin in case that needs to be removed.. just didn't notice it at 1st and thought it was a locating dowel or cover

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11/19/2018 5:54 PM

Thanks for all your comments..
I have managed to remove the Shaft there is a locking pin in the housing that needs to be removed.. just didn't notice it at 1st and thought it was a locating dowel or cover ..

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11/19/2018 10:26 PM

Kiwikemo wrote:

Run 40:1 Belray 50:50 Avgas and 98... I've seen other bikes with a lot of oil residue that running 50:1

Underground wrote:

Jetting is obviously rich then

Tracktor wrote:

Too much oil in the PV assembly has very little to do with air/fuel ratio, lol.........

You've never had clean jetting before then. If you have unburnt fuel, which is a byproduct of overly rich jetting in a two stroke and why they have trouble clearing emissions, you're going to get an emission, being a mixture of unburnt fuel and oil and carbon. And I've never had PV seizers, galling, marking or stiction in any of my 6 2 strokes I've owned with a PV or the hundreds I've tuned. Whatever. Enjoy the black goop clogging up your PV system, exhaust pipe and muffler packing, and your engine running at a lower state of tune, responsiveness and fuel economy. If ride off road, that last one makes a big difference in the amount of time you'll be in the pit lane fuelling up.
Drool on boys.

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11/20/2018 11:05 AM

Underground wrote:

Jetting is obviously rich then

Tracktor wrote:

Too much oil in the PV assembly has very little to do with air/fuel ratio, lol.........

Underground wrote:

You've never had clean jetting before then. If you have unburnt fuel, which is a byproduct of overly rich jetting in a two stroke and why they have trouble clearing emissions, you're going to get an emission, being a mixture of unburnt fuel and oil and carbon. And I've never had PV seizers, galling, marking or stiction in any of my 6 2 strokes I've owned with a PV or the hundreds I've tuned. Whatever. Enjoy the black goop clogging up your PV system, exhaust pipe and muffler packing, and your engine running at a lower state of tune, responsiveness and fuel economy. If ride off road, that last one makes a big difference in the amount of time you'll be in the pit lane fuelling up.
Drool on boys.

Jesus, don't assume quite so deeply chief. Like posted above the oil is there for a reason. Too much would usually be a symptom of a lower flash point of the actual oil being used. Second would be gas/oil ratio. Third might be jetting but the first two are more likely. I have a pretty fast 85 kid & brought another up through the mini ranks who is now on big bikes plus do engine work for quite a few others around. I have plenty of experience with jetting & PV setups which on minis are especially finicky. Especially the KTM 65 where oil build up can have a big effect on performance. Using the correct premix was key along with ratio. Jetting was/is more performance based..............I'm always learning but I can say our 85's run the cleanest of most everyone we line up against.............

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11/20/2018 2:24 PM

On the jetting, I always raise the needle clip 1 notch if it's brand new. They always put them out rich just to be safe. Here's shot from a service manual. This website has a lot of manuals online. Probably not a 2019 diagram but the mechanics of the YZ power valve is fairly simple. None of the 85 manuals on there have power valves so the link is for a 125.

https://www.manualslib.com/manual/581532/Yamaha-Yz125-D.html?page=75#manual.

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11/20/2018 3:32 PM

Tracktor wrote:

Too much oil in the PV assembly has very little to do with air/fuel ratio, lol.........

Underground wrote:

You've never had clean jetting before then. If you have unburnt fuel, which is a byproduct of overly rich jetting in a two stroke and why they have trouble clearing emissions, you're going to get an emission, being a mixture of unburnt fuel and oil and carbon. And I've never had PV seizers, galling, marking or stiction in any of my 6 2 strokes I've owned with a PV or the hundreds I've tuned. Whatever. Enjoy the black goop clogging up your PV system, exhaust pipe and muffler packing, and your engine running at a lower state of tune, responsiveness and fuel economy. If ride off road, that last one makes a big difference in the amount of time you'll be in the pit lane fuelling up.
Drool on boys.

Tracktor wrote:

Jesus, don't assume quite so deeply chief. Like posted above the oil is there for a reason. Too much would usually be a symptom of a lower flash point of the actual oil being used. Second would be gas/oil ratio. Third might be jetting but the first two are more likely. I have a pretty fast 85 kid & brought another up through the mini ranks who is now on big bikes plus do engine work for quite a few others around. I have plenty of experience with jetting & PV setups which on minis are especially finicky. Especially the KTM 65 where oil build up can have a big effect on performance. Using the correct premix was key along with ratio. Jetting was/is more performance based..............I'm always learning but I can say our 85's run the cleanest of most everyone we line up against.............

Moving parts need oil I know. Just not that much. And it's never going to be dry in a 2 stroke I know that too No matter the jetting. Try Motul 800 at least 50:1 if you're still having sludge problems.
I had a bad yesterday so probably kicked off little too much sorry

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11/20/2018 4:41 PM

toomey706 wrote:

On the jetting, I always raise the needle clip 1 notch if it's brand new. They always put them out rich just to be safe. Here's shot from a service manual. This website has a lot of manuals online. Probably not a 2019 diagram but the mechanics of the YZ power valve is fairly simple. None of the 85 manuals on there have power valves so the link is for a 125.

https://www.manualslib.com/manual/581532/Yamaha-Yz125-D.html?page=75#manual.

This is what we call bad jetting advice right here.
As long as the oil is liquid and like how it is the picture it is fine.

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11/21/2018 11:15 AM

Underground wrote:

Moving parts need oil I know. Just not that much. And it's never going to be dry in a 2 stroke I know that too No matter the jetting. Try Motul 800 at least 50:1 if you're still having sludge problems.
I had a bad yesterday so probably kicked off little too much sorry

No worries. I think we are on same page just got lost in translation which happens on the interwebs. Sounds like you work on quite a few bikes so have the correct assumption that most have no idea what they are doing. The stuff I see/hear in the mini world can boggle the mind. Guys pay thousands for engine work but have no idea about tuning them in. Or conversely buying "race gas" to make that stock bike faster. I mean it's gotta be better it's called "race" right in the name?........... We have been accused multiple times of running mod motors when simply running well tuned stock setups and a kid twisting grip...........My favorite is HP2 which we run at 40:1 with a mix og 50/50 non-ethanol & avgas. I always try to buy fuel from same station for consistency........

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