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YZ250 Power valve linkage in wrong position? Dowel pin doesn't line up

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Hello everyone,

 

I'm gonna try and get pictures as soon as possible. But I think there is an issue with the motor that I can't seem to solve. I hope someone has advice on this.

The power valve shaft has a slotted end to make sure the linkage is fitted on correctly. The entire power valve assembly itself is connected up. But as soon as I want to connect the power valve linkage (the part in which you need to insert the dowel pin if you want to screw it in/ unscrew it) then I have to put ALOT of preload on the power valve linkage to make it fit (pull the power valve linkage upwards).

Also: once it is installed, the fork to set the dowel pin in doesn't line up with the hole in the cylinder whatsoever. The fork structure is left of the hole and I cannot rotate the shaft any more counterclockwise (complete dead stop). I can only rotate the power valve clockwise, but I need pliers to rotate the shaft clockwise, alot of force is needed.

I have a suspicion that the rotation of the shaft is wrong, but I can't find how as everything is in place as it should be. Last time it was revised by a mechanic and I found it this way. I couldn't insert the setpin because the hole didn't line up with the fork.

This is a stock image from the interwebz: (not my bike)

 

DSCN0842.jpg.c87ea19c792e7a80fa6773b6380c4d57.jpg

 

 

Edited by 3sly

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The slot is for a pin that comes with bike brand-new.  It's so you don't put pressure on powervalve when tightening /loosening.  But it should pretty much line up no problem.  I'd say your mechanic doesn't know how to time powervalvesvery well just saying.  If you can post pics he may have shaft 180 off or something.  That a pretty simple system.  

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Jep, thanks for the reply. I know that the dowel pin is to be inserted to get the strain of the linkage and power valve assy when tightening/loosening the screw. But I don't understand why the fork doesn't line up with the hole? I can't insert the dowel pin because of that. Also: to get the linkage onto the power valve shaft, I have to pull up the linkage alot to connect it to the shaft. Any idea what might be causing this? (The shaft should be inserted correctly: slide it in and the rotate the slotted side upwards).

 

Pics to come

Edited by 3sly

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13 minutes ago, 3sly said:

Jep, thanks for the reply. I know that the dowel pin is to be inserted to get the strain of the linkage and power valve assy when tightening/loosening the screw. But I don't understand why the fork doesn't line up with the hole? I can't insert the dowel pin because of that. Also: to get the linkage onto the power valve shaft, I have to pull up the linkage alot to connect it to the shaft. Any idea what might be causing this? (The shaft should be inserted correctly: slide it in and the rotate the slotted side upwards).

 

Pics to come

Have you had the side case cover off recently?  Does the arm have spring tension feel when pulling up? Wondering if the arm isn't in the slot of powervalve govener or something.  If not you may have to inspect deeper into it. Usually you have to maybe pull it up just a tiny but and it's on. Ya post pics someone get you straighten out :thumbsup: 

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If you are struggling to line it up there are 2 pieces that can snap off the powervalve and jam it.

One is the little pin on the top that was introduced to hold the valve shut and stop it fluttering. This can snap and jam under the rotating shaft.

The other is a section of the stop machined onto the valve shaft just above the flat section that sits in the exhaust port. I've had this happen and it jams the valve open slightly.

Some more disassembly required to find out though.

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Drain the coolant, pull the radiators and take off the PV cover. It's probably what richg is describing or one of the Allen screws backed out and something came apart.

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This is what is looks like: As you can see the pin doesn't line up in resting position. The power valve shaft cannot be rotated any more to the left, dead end. Only to the right when I pull up the linkage arm (requiring quite a bit of force). Indeed something that's broken? Can someone indicate which part it is on this picture to see what you are talking about that is probably broken. Thanks!

 

 

IMG_20170608_160238_01.jpg

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Why whatadayaknow guys, The fine people from thumpertalk knew the answer yet again. I took of the power valve cover and guess what I found inside stuck onder the right side.

This piece!! 

I just read it is a common issue and does not need replacement, correct?

 

 

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Why whatadayaknow guys, The fine people from thumpertalk knew the answer yet again. I took of the power valve cover and guess what I found inside stuck onder the right side.
This piece!! 
I just read it is a common issue and does not need replacement, correct?
 
 

Hey yeah! Chuck that little peg over the hedge and don't loose sleep over it. It'll cost 150.00 for a new one. The earlier bikes didn't have it anyway.

Thanks for updating us on the fix. There are a few around that grab the advice and never update on the cause.

The other bit I was talking about is as shown. When it happened to me the bike was tricky to start cold.

20170608_172036.png

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Haha np. I don't like that as well, so i definately wanted tot keep you guys updated. 

I'm so happy about this fix. Because after redoing the top end and a complete rebuild of the bike, I don't have any money left :p.

Plus it might explain why the bike smoked alot of fuel at low end and had a loss of power (reason why I did the top end). I'm a novice rider so I don't scream with a 250 2stroke like I should.

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