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Yz 250 1998 Power valve removal Help.

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Hi, Been struggeling for 4 hours now to remove my power valve. Seem to move from side to side like 5mm but cant seem to get them out. Removed all the parts and seals. Whats keeping the power valve in?

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Check the parts diagram removed everything there. Is there a special way of removing the power valve?

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There is an allen bolt that goes through the power valve itself, when you remove the allen bolt, the valve comes apart in 2 pieces, one from each side. To loosen the bolt, you need to put something in the exhaust port to keep the power valve from rotating, a hammer handle works pretty well, just don't use something metal that could damage the valve.

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carefull when separating the valve as there are dowels that can fall out and down the engine.

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Take the left hand pv out of the left hand side. Then reinstall the long allen bolt into the right pv and pull it out. If its stuck put the allen bolt thru a socket at use it as a puller to jar it loose. Turn the crank so the piston blocks the case keeping the two dowels out of there, assuming its still on the bike

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Thanks for all the help this forum rocks :smirk: . Next step to file the power valve its touching the piston

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its touching cause the stopper is worn down and its turning to far into the piston.

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But filing the power valve will work? The stopper is quite worn. Its only touching the piston barley there is like a polish line on the pistion

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Filing the valve will change the shape of the valve and could have an affect on power.

You don't need to file it, you can just build up the stopper so the valve will return to its normal position. I have drilled the stopper, threaded it and inserted a small screw before. You could also build the stopper back up with something like J-B Weld.

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File or build up the stopper. Either will work. I always filed mine since I had no welder. The power may change a little, but I never noticed.

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Good idea to match them as well, since you have it apart... I would have never noticed unless it was pointed out to me. If you look at them side by side you will notice one is larger then the other, if your feeling ambitious you can also match them to the exhaust port when in the open position. Suprised you didnt mention that Roland. :smirk:

Heres a visual for you from my rebuild... notice how it is uneven in the picture

IMG_0542-1.jpg

and after it was filed down... its not much material to take off but after Roland mentioned it I did a little research and it is supposed to give pretty good performance increases.

IMG_0540.jpg

IMG_0543.jpg

IMG_0546.jpg

Edited by BDubb106

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I meant to mention it, but I hate to sound like a broken record. It made a HUGE difference in the way mine ran, though, and is well worth the time it takes.

How can you not love this powervalve design? After the first time, servicing it is simple. Its dependable, reliable(mostly) and it works 85% as well as the new one. I'm all for progress, but this design rocks.

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I havnt had the chance to get mine all the way back together yet, let alone ride it... so I personally cant speak on how much of an improvement it really made, but from what I gather your right on the money. Its supposed to give pretty darn good gains from midrange and up. I havnt seen a bad review of having the PV matched nor have I seen any negatives to be had from it.

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I had 1 power valve fall apart,bolt must have stripped and it worked out.It came close to losing the dowels in the engine,even the dowel holes were worn from the valve not being tight.I wondered when we installed the new valve if I should have used locktite,even posted on it but didn't get an answer.Ended up not using it as I figgured the heat would break it down anyways so if you take it apart make sure to torque it properly and maybe check it after a few rides.

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Awesome info thanks will def file and match the power valve. Busy rebuilding the whole bike will start a new tread and post pics. Process is quite slow parts are expensive over here. Once again thanks for all the info :smirk:

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I always thought the pv loosened from rubbing the piston. No proof, but my bike reacted like this

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Busy rebuilding the whole bike will start a new tread and post pics.

Awesome another rebuild coming up :smirk:

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