PSA: clean your rave valves!!!

[purple_people_eater]

Got a little pic of what happens when you never clean your rave valves for you guys. This ski came in seized, I rotated the crank backwards and it freed up, tried starting it and I ran terribly for 10 seconds and resized. I told the guy he needed a new motor and that I had a used one if he wanted it (the motor out of my xp). He told me to go ahead. I'm striping the old motor down and I had to pry these out.

Moral of the story: keep up on your rave valve maintenance.

 

[brian0516]

Don't have raves. What should a good clean set look like?

 

[68ragtop]

Interestingly, I was going to make a post a while back about a pair of one owner GTX's I purchased. Both had failed cranks. One of them was at 85 hours, & on that one the paint was never broken on the rave bolts. I was shocked to see they where not all that bad. Dirty, sure. But not gummed up or stuck at all. They moved very free. That surprised me a bit.

Is that how they looked coming out? they look pretty clean other than what looks like rust?

 

[purple_people_eater]

He must have been running xps- syth then. This guy wasn't. This ski had right at 150 hours. Which is right where the rave valves need clearancing as it is imo. It was the perfect storm.

 

[68ragtop]

He must have been running xps- syth then. This guy wasn't. This ski had right at 150 hours. Which is right where the rave valves need clearancing as it is imo. It was the perfect storm.

Yes, he always ran XPS & the dealer was just down the road from him. But, these skis are evidence that XPS will not save your engine from internal rust. He never fogged them. Not once. He didn't even know how & said the dealer took care of them at the end of each season. Its the"during" season that ultimately did them in IMO.

 

[purple_people_eater]

Most people don't realize how important it is to blow the water out of the exhaust after pulling out of the water. That's a main cause of 75% of all water damage on the 787 and smaller motors.

 

[Robj]

Now I am no expert, but it looks like those raves failed due to a clearance issue, being struck by a piston. Even if the raves are dirty what else would cause them to fail other than contact with the piston? My understanding is that dirty raves won't open and close properly. Am I missing something?

 

[68ragtop]

Most people don't realize how important it is to blow the water out of the exhaust after pulling out of the water. That's a main cause of 75% of all water damage on the 787 and smaller motors.

I do this with all my skis after they are out of the water.
(get a lot off weird looks from others at the ramp)
IT does blow out quite a bit, but there is still a lot of water & vapors in the exhaust for many hours after, & water that can evaporated for weeks if not months. I can pull a plug & slide my borescope in the hole & its foggy. 5-6 hours later there are moisture droplets on the cylinder walls & spark plug electrodes. The electrode droplets seem to be more with the DI than other engines, but I am thinking its because they are at the very top of the chamber. If there are any other DI owners reading this thread. Pull your plugs 6 hours after a ride & take a look. you will be surprised, or maybe terrified. lol.

 

[purple_people_eater]

Now I am no expert, but it looks like those raves failed due to a clearance issue, being struck by a piston. Even if the raves are dirty what else would cause them to fail other than contact with the piston? My understanding is that dirty raves won't open and close properly. Am I missing something?

as hours go up the diameter of the cylinder sleeves get bigger. the rave valves stay the same. not about 150 hours is when the rave valve clearance needs to be checked and addressed on any rave engine. one these, not only where they stuck from the combination of wrong oil/never being cleaned, they where the down position and instead of just nicking the rings like what will usually happen (cause normally they would be moving) they did have a full on meeting with the pistons. also when they stick that get really hot and start to weaken and form cracks. like i said, this motor was a perfect storm of everything bad that could happen.

 

[spx800]

How much are you supposed to machine off? Is this in the service manual?

 

[purple_people_eater]

About .5mm. And yes it is in the manual.

 

[spx800]

good to know. Would machining them early present problems?

 

[purple_people_eater]

Yes, around 130 hours should be safe.

 

[BigAl57]

Probably a dumb question but how do you blow the water out of the ski when you take it out of the water?

 

[purple_people_eater]

Probably a dumb question but how do you blow the water out of the ski when you take it out of the water?

After pulling out start the skis up and rev to 5k once or twice.