Powervalve hitting piston
- Thread starter summ8rmk
- Start date
JasonAK is on the money, the inside of the valve pocket gets smashed in so the valve can travel beyond fully closed and kisses the piston. Easiest way to get around it is to relieve the valve blade so it has clearance when fully closed.
cuz we are in the cat section.
they all have some problem the 800 cat just not as many.
we also don't have 2 dozen thread on what is the best fix kit either.
It is not real common. I have only seen it a few times in thousands of motors that we have seen.
Take a look at the exhaust valve.
The buildup of carbon has not touched the piston.
After removing the carbon, u can see where the piston polished the valve.
.
How is it possible? The valve contacts the piston, wear is evedent on both parts. A layer of carbon thicker than the material removed builds up and doesn't contact the piston.
GS6
The buildup of carbon has not touched the piston.
After removing the carbon, u can see where the piston polished the valve.
How is it possible? The valve contacts the piston, wear is evedent on both parts. A layer of carbon thicker than the material removed builds up and doesn't contact the piston.
GS6
Because the contacted between the piston-powervalve happened some time ago. Then the powervalve stop, stoped being deformed/smashed any further. I bet if you look at the powervavle stop/seat you will see a slight inprint, not as bad as the other cylinder that has worse damage.
I understand what u are saying.
Here is what i have an issue with.
Take the wear from all 3 (piston, valve, valve stop)add them together and that value is less than the value of the carbon buildup. The clearance from carbon buildup to piston ring is closer now than when new.
So this damage occurred hundreds if not 1,000 miles ago.
Could this be related to heat expansion? Could running the engine at the leanest rpm(ie:5,800) for a long duration cause extreme EGTs and the valve expand into the cylinder?
Or piston and cylinder expanding?
GS6
Here is what i have an issue with.
Take the wear from all 3 (piston, valve, valve stop)add them together and that value is less than the value of the carbon buildup. The clearance from carbon buildup to piston ring is closer now than when new.
So this damage occurred hundreds if not 1,000 miles ago.
Could this be related to heat expansion? Could running the engine at the leanest rpm(ie:5,800) for a long duration cause extreme EGTs and the valve expand into the cylinder?
Or piston and cylinder expanding?
GS6
Now I feel like I should check mine....man
I bet there is a whole lot more doing the samething, not many people clean there valves like they should. Not only that but if you do clean them and don't look down in there you will never see it. If you would have just looked at your valve you would have had a hard time telling it contacted the piston. Hopefully you can just grind them a bit to keep from buying jugs, that will be spendy if you have to buy new ones.
T
theUltamateTBM
Active member
Makes a person wonder if putting a set of stm valves on from the beginning would make a difference also could the return spring in the valve be to heavy
If ya run yamalube you wont need to clean the valves
in my experience at least. Last when I checked on my last sled everything was gravy at 3800 miles still. Nothing hitting
That transfers the load 100% to the cables instead of relying on the stops as intended by design?
Removing material from the tip of the valve is the correct way to gain clearence.
I am looking for the root cause of this issue.
GS6
This is what I was thinking, must be a way to shim them out to stop this from happening.
Here is a brand new 2016.
Sled has ran for less than 10min.
I wonder if mine happened within the first 10min?
GS6
whos sled is this? my initial thought was this is what happens when you ride everywhere blipping the throttle. pounds down the stops after a while.
I am planning to check my cables to make sure they are adjusted to spec as i am sure the dealer didnt.
maybe i should pull the exhaust and look at this now...
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