Piston pin crooked

[Johnny 5]

I have been building this 62mm bore 60.8 stroke (3mm) motor this summer for my wifes dune 150 that will be 183.5cc. The case boring was fun with the boring tool that we got from ncy.
If I could do it again , would have had it machined at a shop because the bit would some times grab and the case would jump while using my drill on the bench.
Was able to get the case opened up to 65.15mm so the 62mm ceramic srp cylinder would fit. It is thin but I know it will be okay.
My real problem with the 3mm, 60.8 stroke crank is the piston deck height is crooked on the chain side of the cylinder.
I have .025 thous on the chain side and .053 on the oposite side.
When I reinstalled the piston 180 degrees to see if it was the piston or the crank the measurements changed to .025 oposite of the chain side.
So I know the piston pin was machined crooked.
My question is with .025 piston deck height and a .010 head gasket total .035 of a inch is this too tight too run?
Normally I dont check deck height this close on a stock motor, but with the stroker motor I had too mill the cylinder head .015 thous/inch so the timing chain wont be so tight.
I am about to just run it and see if it will live or die.
I may get another piston 62mm too see if the pin hole is the problem.
Any body got deck height minimum specs?
I know stock is safe but stock has been done need more POWER.

[BuggyMaster]

Hmm..that would just eat me up worrying about it. Talk to Tom at SYC motorsports (click banner at top of this page). He knows the guts of these things pretty well. My first impression in reading this is that it wouldn't last too awful long but talk to him and see what he says.

[Johnny 5]

I measured the top ring land to the top of the piston and it is about .035 thicker on the chain side of the piston. The piston is crooked ,the casting was not probally centered when it was machined.
I will say this isnt the first time a problem building a motor has happend to me.
Ordered a new piston from a preformance scooter store for $30.00 rings and pin.
I am probally going to send the kit back, this will be the second bad kit I got. The first ncy 62mm kit had a piston flaw and the cylinder sleeve was off center, and the head gasket was for a 63mm bore.
This is a ceramic nikasil srp kit and it looks good with a thick 1.5mm cylinder wall.
So getting a good piston is the only thing keeping this from coming to life.
I am also concerned about the srp crank 3mm that was deliverd by Ace ventura. The box was probally tossed and kicked a few times and the soaked with water or at least I think it was water. It spins true and looks okay.
So a little set back that time and more money can fix.
I was getting a little bummed out untill I forgot that having these little problems are part of being a buggy nut.
Could almost buy 2 stock motors for how much is now spent on parts and tools, but totally worth the experiance.
I will post back when the piston gets here.

God bless you all and God bless America.

[BuggyMaster]

So is it possible that the top of the piston is thicker on one side than the other? that wouldn't bother me much as long as it is below the deck (i.e. not protruding). Think of the piston designs in cars. Dome pistons, wedge, etc. That would not phase me at all unless after talking to tom there is a hell of a reason to worry me about it.

[x-bird]

ditto the above, i'd check the pin bore from it's bottom to the skirt and from the top to the top of the piston on either side. But by that thinking it could also be that the piston is thin on one side up top.

[Johnny 5]

Well the pin bore isn't crooked. I measured and the piston top is thicker on one side than the other.
Is .030 of a inch head to piston enough clearance?
Deck height is .025 and the head gasket is .010. So . Not counting on the two base gaskets that will compress a little.
So I am thinking min clearance will be .030 . I may get another piston to be safe.
Any ideas?

[x-bird]

Well you could file the thick side down, my only concern would be whether it's actually thicker up top or if one side of the piston top is actually thinner than spec. If that's the case, then you might run into hot spot issues and the possibility of blowing the top out. I'd play it safe and pick up another.

[SYCARMS]

I would send the kit back to who you bought it from. I personally was not impressed with the quality of NYC. A domed piston is just what it says domed. .030 on one side is a defective piston. First there will be a balance problem , second there will be a combustion problem. The idea is to get the biggest consentration of atomised fuel to swirl into the center where the plug fires. With how you explain, it will stop all swirl and push to one side but that is if you get past the vibration. Post some pics for us to see what you see. .025 is the extreem minimum deck height. I would recomend .040-.050 for reliability reasons. I run the minimum but I drag race mine and it gets a tear down anually. Check to make sure that your jug sets perfectly flat on the case with no gasket and with no pressure. Those bore tools are known to bore on an angle to where the cyl will not square to the case. Post some pics of the piston and we can give you a 100% accurate answer.

TOM