Damaged Powervalves, Piston Edge...

S

Spaz's SRX

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I was pulling the valves to clean them for the upcoming season and found two of the three were damaged. The #2 valve is fine, just dirty, but #'s 1 & 3 have some bare aluminum showing and are pretty ugly. This is not on the cable side, it's the edge that goes towards the piston.

What causes this? Can I still run these valves or do I need new ones?

I try and post pics, but I'm having trouble. Keeps telling me my files are too big?
 

if i am understanding you correct the very bottom of the beveled edge is bare ? or the actual beveled edge ? if its the very bottom of the valve edge it sounds like the valves have smacked the pistons ever so slightly ...email a picture of them to me and ill take a look i have seen the valves wear down an go past the stoppers break the blade off and get beat around in the cylinder ..i kept it cause i was amazed the damage it did to valve but didnt hurt piston lseehwtohms@yahoo.com
 
Yeah, the pistons look good, but the valves not so. I will shoot you some pics. tonight when I get home, thanks.

Also, do you have two for sale, price shipped to 61109?

Thanks, again.
 
FYI - I also noticed these two pistons had a dirty burn oil look on the tops, while the middle (clean) one was burned clean on top. This was just observed by looking down the spark plug hole.

Any ideas?
 
if the little stops inside are destroyed..the new valves will pass on thru again and get damaged.I would look into that first..may need new cylinders?????
 
ok after looking at the pictures i was correct the valve has been hitting the piston on them 2 valves which caused the very bottom edge to show bare alumnium which has actually made the edge wider than it is suppost to be ...the line on the top of the valve blade is from the valve getting bounced up and down ...you need to inspect the stopps in the jugs make sure they arent wore down to almost nothing ...without having them in hand to inspect them better and to inspect the stops hard to say exactly what to do ...but from what i can tell the 2 were out of adjustment ..if you were to remove the exhaust and adjust the valves by the flush to port method i would say you can reuse them as long as the stops are not worn off ..but as i said without being able to inspect them in person its hard to say exactly what to do to solve the problem
 
This commonly happens when the engine is run for a while with a cable pull-through or valves extremely out of adjustment. The valve is allowed to bounce freely on the stops that Ya*am*a*head mentioned and it ultimately wears them off. This allows the valve to make contact with the piston. Adjusted properly the stops aren't needed, but if they get far enough out of adjustment, or the cable pulls through or breaks running without stops allows the valve to make severe contact with the piston. This of course can result in catastrophic engine failure.
 
Ding said:
This commonly happens when the engine is run for a while with a cable pull-through or valves extremely out of adjustment. The valve is allowed to bounce freely on the stops that Ya*am*a*head mentioned and it ultimately wears them off. This allows the valve to make contact with the piston. Adjusted properly the stops aren't needed, but if they get far enough out of adjustment, or the cable pulls through or breaks running without stops allows the valve to make severe contact with the piston. This of course can result in catastrophic engine failure.
Click to expand...
Ding ..don't scare the guy...
 
ding aint tryin to scare him ...just giving him the honest truth ...thats the one thing i didnt ask tho is any of them valves pulled thru ? or has the cable started to enbedd itself in the valve top ? if so.... like ding said that would allow the valve to drop slightly causing the piston to slap the valve edge ...in turn wearing the stops down enough to let the valve pass by ....here is a picture to better show what we are discussing
 

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Thanks for all the help guys!

I can tell you for certain that the valves show no sign of "pull through" or any other type of wear on the cable end. They actually look very good.

As for adjusting the valves, I used the method sugested in the OEM Yamaha manual I have. I use two allen wrenches (I think 2.5mm) to set them last year. Thinking back though, one of the valves looked like this last year when I pulled them.

Tonight I will try and take a look inside the cylinders and check the stops.

Again, thanks for the help and I'll revert back with my findings.
 
If you look down in the cylinder head where the valves go in, you will see two "lips" on each side that prevent the valve itself from hitting the piston. They are on the very outside edges.

Please correct me if I'm wrong guys.

I actually just noticed these when I was inspecting for this problem.
 
ok that's what i thought they were telling you ,if so they are wrong. the part that stops the valve from hitting the piston is the larger diameter part of the valve between the blade and the area that the seal rides on,it wears and the area that it contacts in the cyl wears just as they said if the engine is used with valves that are out of adjustment for what ever reason .those two little lips will only stop the valve blade from falling into the cyl if the blade happened to break off from the rest of the valve , actually those two little lips get remove if you get the cyl's trail ported or big bored. to fix the contact problem you don,t need new cly's you just need to have the surface of the valve that touched the piston machined back to give .030" clearence from the piston when the valve is fully inserted into the cyl .
 
Alright, did some checking and found that one of the two "stops" on the third cylinder is damn near gone. And to clarify, I am talking about the ones right next to the piston that the tips of the valve would hit, not what 9801srx was referring too.

Remembering back to last year, I noticed only one of the valves was badly damaged, but I put it back in anyway with no further investigation. I also adjusted the vales last year. So, in conclusion, last year I put a good valve back into the bad cylinder head but I had adjusted the valves, so, that is why the second valve is not nearly as bad when I pulled it out this year.

Hope this makes sense, let me know your guys thoughts.

Can I run the sled for one more season like this, maybe 500 miles??? I only ask because this is probably the last season I will have it.
 
oh ya since you know what cylinder it is causing the problem when you adjust it i would give that cable a extra turn which will hold that valve open a bit and keep it the valve from the piston
 
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