Pro RMK Piston rock (a video-if I can get this to work)

[AKSNOWRIDER]

I would be interested to know how much the diameter of the piston expands when up to operating temperature.
Any thoughts?

I wouldnt be surprised to see close to .005" in expansion on a pro on a long full pull....

 

[AKSNOWRIDER]

You have to be exaggerating. We're talking about 10 thou being a lot. You're saying you have somewhere between 125 and 250 thou clearance between your piston and cylinder?

I think what he is seeing is the fact that the top of the piston where the rings set are about .005-.008 smaller in diameter then the barrel of the piston so it doesnt gurf the ring grooves up...which makes it look like tons of slop........

 

[poorider]

.005 to .008 is a far cry from .125 to .250

 

[skibreeze]

Yes. Three Pro RMKs.
This 2011 2500 miles no engine troubles.

GF 2011 2000 miles no engine troubles.

My 2012 1500 miles no engine troubles.

6000 miles total. 6-9000 feet, rarely on trails, deep heavy Tahoe pow.

It's easy to say that you had no problems when you don't open them up.
Just because you didn't see the trouble doesn't mean it wasn't there.
Mine was running perfectly at 2,000 miles. I opened it looking for trouble and found what I was looking for and more.

 

[skibreeze]

I think what he is seeing is the fact that the top of the piston where the rings set are about .005-.008 smaller in diameter then the barrel of the piston so it doesnt gurf the ring grooves up...which makes it look like tons of slop........

.005 to .008 is a far cry from .125 to .250

You guys are right, but when you are wiggling pistons back and forth, it seems crazy loose.

 

[1Mike900]

Now you have to wonder why rings start flaking off if they are rocking that much? But I bet the top of the piston expands .010 and the bottom about .004 when up to temp? But how much does the cylinder expand .002 to .003? A long rod would put much less side load and less fatigue to the piston and cyl. skirt.

Mike

 

[Murph]

It's easy to say that you had no problems when you don't open them up.
Just because you didn't see the trouble doesn't mean it wasn't there.
Mine was running perfectly at 2,000 miles. I opened it looking for trouble and found what I was looking for and more.

No argument from me on what you said, BUT so far they have run flawlessly. When I pull the cylinders off I'll report back.