Best way to adjust Viper powervalves?

make sure your servo is turning to the full open position before you make your adjustment on the valves.....
i have never used the 12v valve tester to open the valves up so not sure exactly how it works but i have always had good success getting the valves to open up fully by turning the idle down below 900 then hitting the kill switch once the valves open fully..
 
viperino said:
make sure your servo is turning to the full open position before you make your adjustment on the valves.....
i have never used the 12v valve tester to open the valves up so not sure exactly how it works but i have always had good success getting the valves to open up fully by turning the idle down below 900 then hitting the kill switch once the valves open fully..
Click to expand...

This was the way I was told so I ran it under 1000 RPM's and they went to full open...killed the motor and then replaced everything. (all 3 pulled thru and one cable was shot)
Now I read this and am confused as to what is the cylinder wall and what is the port when I am reaching up in there. 2 of my cables were fine and I did not touch them. Just replaced the valves. One cable was bad. I set the new cable about where the other 2 were on the spacing up by the servo and they all seem pretty close to the same as I reach up in the cylinder. I can tell where the valve is reaching up there because when I can push on it so I know thats the valve I am touching. What I am still confused on setting these flush with the wall when they are wide open??? To me this still makes no sense since they will close when the motor is started and then wont they be to far in??? only thing I can think of is that the taper on the front of the valve is what allows for piston clearance???? I don't know...
I sent yamaholic22 a PM and hopefully he reads it and I can clear this up. He was very helpfull in a thread I started on the same subject on my SRX when I noticed it was not hitting max RPM's.
If he gets back to me, I will post what he said...
 
ssviper, I think that pic of your servo is in the closed position. This is what I do when I adjust my pv's. ( I clean them and adjust them like this every 500-800k) A little obsessed I know.lol
Start up your sled and warm it up some. With your servo motor cover off.
Now as you turn down the idle to below 1000rpm, you will see the servo motor turn counter clockwise. Kill it when you are at about 900 rpms. Your servo motor is fully opened now.
Now before you do any thing take a center punch or something and mark the servo motor wheel ( that's what I call it- where your cables attach) with one punch mark and one on the housing that the wheel is connected to between the two top philips screws in your picture. Or use a sharpie pen. I use a center punch so the marks will be there for future adjustments.
Ok, so rip off the pipes and the flanges. Feel inside and adjust the cables at the servo motor. If by chance you happen to turn the servo wheel any you can gently turn it back so your marks line up again. Loosen the locknuts and start adjusting till you feel the valve is flush at the port. Tighten down the lock nuts. After I take her out for a test run, I do the idle down again with the servo motor cover off just to check I got the motor marked in the fully opened spot.
Put it all back together and if it was done right you will hear and definately feel the difference. Sound is crisper and power is better.

mul
 
right- and i think you want to wait a few seconds while it's idling low- my servo was rotating back and forth a few times and then it went to fully opened and stopped. that's when you want to shut it down.

s.s. viper- ya, something doesn't look right there. this is my first time doing it this way too, but my cables are all tight and the valves aren't down in the port. maybe you're not waiting long enough for them to settle down into their position before you shut it down? also- just a thought, have you cleaned your PV's? they might be stuck like that or your cables have pulled through?

bigmac- i think you're right about not taking into account for cable stretch- making them all different. i'm not even going to do it that way any more- just gonna check em in the ports like yamaholic says.

snowdog- the exhaust port is the immediate hole you see when you take off the y-pipe, the cylinder wall is in further, the area that the piston rides up and down in and is very smooth.
 
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Millinocket Rocket said:
snowdog- the exhaust port is the immediate hole you see when you take off the y-pipe, the cylinder wall is in further, the area that the piston rides up and down in and is very smooth.
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When you say "in further" you mean in twards the piston or up the cylinder wall twards the valve? All I know is I reach up there and I THINK all three valves are out (or twards the front of the sled) just a bit. I can feel something recessed maybe 1/2 a MM and I can push on it and it returns like it's the valve. Anything below that feels like the cylinder wall to me. And again, can anyone explain how they don't hit the piston if were adjusting them flush when they are pulled open? Once the moror starts isn't that servo going to return them twards the cylinder when the cables get released thus putting thme out into the cylinder?
 
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There is a positive stop in the machining of the slot that the PVs ride in. There is no way for the valve to catch a piston short of the machining in the cylinder itself failing. If the failsafe was not there people would be screaming all over the place due to engine failures from pull through and cable failures. improperly adjusted valves simply do not raise the port roof to as designed so you don't make the power you should.
 
SNOWDOG said:
When you say "in further" you mean in twards the piston or up the cylinder wall twards the valve? All I know is I reach up there and I THINK all three valves are out (or twards the front of the sled) just a bit. I can feel something recessed maybe 1/2 a MM and I can push on it and it returns like it's the valve. Anything below that feels like the cylinder wall to me. And again, can anyone explain how they don't hit the piston if were adjusting them flush when they are pulled open? Once the moror starts isn't that servo going to return them twards the cylinder when the cables get released thus putting thme out into the cylinder?
Click to expand...

that thing that you're feeling that you push up and returns is the valve. if you loosen the adjuster nut for the cable, you will feel it come down flush as you're adjusting it. then re-tighten the locknut on the cable. do this to all 3.
 
Millinocket Rocket said:
that thing that you're feeling that you push up and returns is the valve. if you loosen the adjuster nut for the cable, you will feel it come down flush as you're adjusting it. then re-tighten the locknut on the cable. do this to all 3.
Click to expand...

Thanks for the explanation Eric...
and Millinocket...this is what I figured. I adjusted them flush and put it all back together. I'll have it on the snow this weekend to see how it runs. Has to be better than what I had with three pulled thru valves.
It sure sounded good on the stand....

Thanks again you guys....
 
so since i have a ER i turn the key on but not run and that makes the valves go to full openthen shut the sled off with the the kill switch. feel the power valve through the manufuld and it should be flush with the wall is that the top thats flush or the coned edge. any one in the rochester ny area want to help me on this.


thanks
 
Yes like daman says, read the tech pages and search.

I am afraid you guys may be making this more complicated than it needs to be.

The valve simply adjusts the port height (the timing of when exhasut gases can escape from the cylinder). It is the vertical height that matters the most.

The pic that S.S. Viper posted is in the closed position like he suggests. He likely did this so you could see the valve. His advice is good too, you want the leading edge of the valve to be flush with the passage when the servo is at full open. Using the starter (choke) flipper is the easiest way to get it to idle down to 900. Marking the pulley like suggested is a good idea.

Someone else mentioned feeling for a thin piece that moves to find the valve. This is very easy once you have done it a couple times. In fact if you push the valve up it will only go so far and stop. This is the Yamaha adjusting measurement in the manual. Remember you want to adjust the leading edge (towards the cylinder) to flush at full open. The valve end is machined so that both edges will likely be flush, but the leading edge is the important one.

The Yamaha method does allow for stretched cables. What you are really measuring at the housing is how much free play there is at the full open position. The valve will actually travel on into the housing a certain distance before bottoming out. This is method is not as accurate as the "feel" method, but it is close enough for those who are not looking for optimum results.

Yes, there is a stop machined in the cylinder that the 2 tips of the exhaust valve will rest on if it is allowed to drop freely. However, if run long enough the softer valve material can peen over and contact with the piston can occur. I have seen several like this, but all of them were run quite a while with a pulled through or broken cable.

Not trying to insult anybody, just trying to help. These valve are very easy to adjust really.
 
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