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Discussion Starter · #1 ·
I'm in the process of installing a RE 14:1 piston and when I went to check my deck height I found the piston is above the cylinder about .0035". I'm running a stock yamaha head gasket and I think there only .015- .020" thick. So that would leave my piston to head clearance around .012- .017" and it should be closer to .040" from what I understand. What can I do about this? Run two base gaskets? Or a thicker cylinder or base gasket? Does anyone know the compressed thickness of an oem head gasket? Or should I just bolt this thing up and check the piston to head clearance? :confused:
 

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Did you mill the cylinder or something? It shouldn't be above deck with a base gasket.

When I did my build, my target was .015 below deck with piston at full tilt. I know others run closer tolerances, but I just didn't want to risk it for such minimal gains.
 

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Discussion Starter · #3 ·
I leveled the cylinder with 800 grit but i only removed a thou or two. The base gasket is in and torqued down and the face of the piston is right around .003 to .0035" above the deck with ne head gasket on.
 

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Discussion Starter · #4 · (Edited)
I'm pretty positive I can't run with the piston up this high. So, what are my options? Can I just throw my old base gasket in the so i'm running two base gaskets? That should be enough to drop my piston in the hole a bit. Or should I run a cometic head gasket? I believe they are thicker?
 

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If it were me, I'd stack a base gasket or two, but I don't like piston to head contact. Been there....done that. I would also clay it before I ran it to check valve clearances.

Yes, you can re-use your old base gasket as long as it's in good shape. I would run OEM head gasket over Cometic.
 

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Discussion Starter · #6 ·
Yeah I hear cometics are not ideal. I think I have three base gaskets lying around. I plan on claying to check piston to valve and piston to head clearance. I think piston to head should be .040" min and piston to valve should be .080". Does that sound right?
 

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Discussion Starter · #8 ·
I'm also curious why my piston sits so high in the first place?
 

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Discussion Starter · #10 ·
I don't think so but it could be possible. Thanks for all the help wobble.
 

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Discussion Starter · #11 ·
So, I was looking at the deck height of the piston again and when the piston is fully tilted to the front or back im measuring around .015" above the cylinder. It seems like I have a ton of rock in the piston. Is this normal? I attempted to measure piston to wall clearance and it was minimal on the piston skirt but quite loose up at the rings. Not sure what to do at this point. The cylinder only has 15 hours on it and looks good. Its not wore out at all. The piston is used but in good shape. If it's .015" above at full rock I will need to go around .030" bigger on the base gasket just to get the right piston to head clearance. Any suggestions? Or am I fucked? :confused: I think White Knuckle makes a .060" base gasket but I think that too big. And now i'm worried about all the rock in the piston... :banghead:
 

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First verify your base gasket is there, hopefully it's not.. Then check the P/H clearance at the wrist pin location on both sides, take the tallest. Don't worry about the piston rock, when the top of the piston gets hot, it will expand a great deal, thats why the skirt is tighter at this point. Base gaskets come in two sizes that I know of, .009 and .019. They can be stacked for a cheap fix, not the best but I've done it. If I remember right, a stock head gasket is .012, a cometic is .027, and the SCE copper is .041. Your right in my opinion at the .040 P/H, everybody is different and some will tell you head gaskets will live longer above .045. I've also heard of shops targeting .050, I feel this is excessive but if your building a long life motor, carbon buildup has to be accounted for. If none of this works, call John.
 

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Discussion Starter · #13 ·
Thanks man. This information has been helpful. Yeah unfortunately my base gasket is there. I didn't measure the piston height above the wrist pins just on the flat portions in front of the valve reliefs. I'm going to try to stack three oem base gaskets and see if that drops it down enough. Where would I get a thicker base gasket? The oem ones only come in one thickness that I know of?
 

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I think it's best to call Racers Edge and to ask for the total cylinder length, from the base of the cylinder to the deck, and then measure yours with a good set of dial/digital calipers... that way you can at least tell if you're cylinder is out of wack or something else is the issue. I very much doubt you took more than .003" off the cylinder, but weirder stuff has happened.
 

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Cylinder is 4.041. If you were not mearuring over the wrist pins you may not have a problem at all. If you do infact have piston above the deck, it would be great to find is an older style piston before they corrected the C/H, otherwise the basegasket is your only option. I think cometic makes the .019 thick ones.
 

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Discussion Starter · #16 ·
My cylinder measure in right at 4.039-4.040. I'm going to need to install my cylinder again and check the piston height. If its still above the deck i'll have to stack base gaskets. I have four base gaskets so I'll stack them until I have enough piston to head clearance. My only issue now is figuring out a way to measure the piston height above the wrist pin? There is only a small shoulder there before the height of the piston changes and its going to be hard to get a straight edge there. And if the pistons below the deck how would I go about getting a feeler gauge in there? Maybe a depth mic?
 

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My cylinder measure in right at 4.039-4.040. I'm going to need to install my cylinder again and check the piston height. If its still above the deck i'll have to stack base gaskets. I have four base gaskets so I'll stack them until I have enough piston to head clearance. My only issue now is figuring out a way to measure the piston height above the wrist pin? There is only a small shoulder there before the height of the piston changes and its going to be hard to get a straight edge there. And if the pistons below the deck how would I go about getting a feeler gauge in there? Maybe a depth mic?
You can clay it, after you get it below the deck warm up some clay with your hands, put it on the piston, and turn it over by hand. Make sure to put a light film of oil on the head. Then take the head back off and cut into the clay and measure it with a dial caliper. But I'm wondering more why the piston is so high if the deck height of the cylinder is within spec.
 

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.038 - .045 is your target, We are a cometic dealer and if you need custom base gaskets made let me know and I will hook ya up. I dont recommend stacking gaskets, everyone has done it and it will work for awhile but it will start to seep after time. Do it right the 1st time and you wont be sorry later that you took a short cut!!

Cometic comes in fiber gaskets, .012, .015, .020, .031, .039, .047, .060 and larger as well

Steel they come in .010, .014, .020
 
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