Power Valve Hit Piston

crossfire879 · Oct 17, 2014

I got a 08 M8 with ported jugs and shaved head. Since then twice now the clutch side piston has come in contact with the power valve. Its minimal contact because it never harmed the rings, just marked the piston. The first time I tried grinding the valve a bit but it never fixed the problem. However with everything apart and rolling it over by hand i can physically see clearance there?? Is it possible that the stopper inside the valve assembly is hammered out and letting the valve drop down too far momentarily while in operation? Even with the valve bolted into the cylinder and piston out i checked and the corner that hit the piston is no more than flush with the cylinder wall. The guy who did my porting is busy and i am having a hard tome getting a hold of him.

backcountryislife · Oct 17, 2014

crossfire879 said:
I got a 08 M8 with ported jugs and shaved head. Since then twice now the clutch side piston has come in contact with the power valve. Its minimal contact because it never harmed the rings, just marked the piston. The first time I tried grinding the valve a bit but it never fixed the problem. However with everything apart and rolling it over by hand i can physically see clearance there?? Is it possible that the stopper inside the valve assembly is hammered out and letting the valve drop down too far momentarily while in operation? Even with the valve bolted into the cylinder and piston out i checked and the corner that hit the piston is no more than flush with the cylinder wall. The guy who did my porting is busy and i am having a hard tome getting a hold of him.

Porting won't allow the guillotine to drop further down, not sure how that would be a factor.

I'd assume that somehow the stop has simply worn, perhaps adding more gasket would be all that you'd need? I've seen it happen many times, but only from one actually being broken.

Check your adjustment specs too.... but it should be physically limited from going that far, so that should be a non issue.

Cat800 · Oct 17, 2014

Do a search on this issue, there is some info about it.

If you look on the jug where the power valve stop is. I bet you see the stop has made an indentation in the jug causing the power valve to touch the piston. You may see clearance now, but if you see where it is has been hitting. I bet when it's warm and everything is expanded is when it's making contact.

Grind down the corners of the power valve and-or double gasket the power valve.

Btw if it's hitting the piston, it's hitting the rings. Rings are harder than the piston, so you probably don't see where it's hitting the rings

crossfire879 · Oct 17, 2014

backcountryislife said:
Porting won't allow the guillotine to drop further down, not sure how that would be a factor.

I'd assume that somehow the stop has simply worn, perhaps adding more gasket would be all that you'd need? I've seen it happen many times, but only from one actually being broken.

Check your adjustment specs too.... but it should be physically limited from going that far, so that should be a non issue.

Yeah the porting should have nothing to do with it. The original pistons have close to 3000km on them and were fine when i pulled them and i got half a season on the new ones and seen the mark. I measured the lip inside the jugs and they are both the same. I am going to takr the valves apart when i get home and see if i find anything.

crossfire879 · Oct 17, 2014

Cat800 said:
Do a search on this issue, there is some info about it.

If you look on the jug where the power valve stop is. I bet you see the stop has made an indentation in the jug causing the power valve to touch the piston. You may see clearance now, but if you see where it is has been hitting. I bet when it's warm and everything is expanded is when it's making contact.

Grind down the corners of the power valve and-or double gasket the power valve.

Btw if it's hitting the piston, it's hitting the rings. Rings are harder than the piston, so you probably don't see where it's hitting the rings

Yeah it pushes the rings in as it goes by. I will attach a picture whe i get home to my computer.

crossfire879 · Oct 17, 2014

Heres a couple pics of the piston...

sledtahoe · Oct 18, 2014

mod

I believe there was a spacer mod on the 7 to 800 jugs call eric at racin station or something like that I'm sure would shove you problem good luck!!

zachman33 · Oct 18, 2014

I tore down my motor a couple of weeks ago and have the same issue on both pistons. I have my power valve cables adjusted to cat specs. So is there a spacer that wears out!

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zachman33 · Oct 18, 2014

Where exactly is this spacer?

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Rixster · Oct 19, 2014

Yeah this was an issue, after a while the stop inside the cylinder gets a little hammered out and lets the valve touch the piston. It is just aluminum and gets smashed pretty easy. I think the valve part is steel you could either add a little material to that part of the valve or try to add a little material to the cylinder. I would just weld a little on the valve and grind it down to add just a few thousands.

zachman33 · Oct 19, 2014

Can the power valve housings get worn out? As in that internal bushing gets worn out and allows the power valve to twist or move? The power valve is hitting on one side of each piston.

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arctic2009 · Oct 20, 2014

Check item number 13 as well as 14 for obvious wear. I would also check the screw (number 11) inside of the stopper that holds the valve for wear.

summ8rmk · Oct 20, 2014

The tab on the valve sets in the notch in the jug. That is what prevents the valve going in to the cylinder. Not the cables, not the washers, not the gaskets, not the bolts, nothing but the valves against the jug.

zachman33 · Oct 20, 2014

Ok so what parts do I need to fix this problem? All new power valve housings and grind the valves down further? What's a fix?

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ACMtnCat · Oct 20, 2014

On your '09 the fix is to grind the tip of the valve.

crossfire879 · Oct 21, 2014

I used a depth micrometer to measure that lip on both jugs and both were the same all the way across. So not sure why its only happening on one side on one cylinder. Still waiting for a response from racinstation to see if he has some kind of shim or mod to remedy this. I also ordered new stops and pins for the inside of the valves. So i am going to change those pieces, put two valve gaskets down, and grind a little more off the valves. That should take care of it but I will keep a close eye on it and check it often once im riding it. Thanks guys.

Jonathanpitzl · Oct 21, 2014

same thing happened to my ported crossfire 700, i replaced cylinders with stock because one of the ported cylinders were shoot, the clutch side was the one that hit. it was an expensive fix.

kiliki · Oct 21, 2014

some times the side to side of the jug gets worn not just the stop. pull the valve and grind the same angle but just take off 20-30 thous off the out side edges and this will fix what you need even if the side to side is out of speck.

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Power Valve Hit Piston

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