piston slop?? help!!

[RideRed400StYlE]

I recently bought a used 426 kit for my bike. it came with a cylinder bored out for a 426 and a JE high comp piston. or at least it was supposed to be. well the thing i noticed was that the piston said 87m on the bottom. and I know that this would make it a 416 instead of a 426. I figured the hell with it I will just install it because I really dont have time to wait for these corrections I need to have this finished in like 2 weeks at the latest. but anyways. I went and installed the piston and slid the cylinder on, and brough the piston to tdc and it looks like there is a small space all the way around my piston. and if you hold the top of the piston you can move it back and forth slightly. is this normal? or did I maybe recieve a 416 piston and a 426 cylinder. I need any help I can get asap!!

[Guy400]

Don't even bother trying to run the motor if you see daylight between the rings and the cylinder walls. Mic the cylinder and verify the bore and then get the correct piston. All you're going to do if you try to run the engine in it's present form is burn more oil than you can pour into the engine, risk damaging the engine severely from the piston rocking and have about 0 compression.

[RideRed400StYlE]

its not that much of a gap. you cant even see the rings. but between the top of the piston and the cylinder wall there is a little space. and you can move the piston each way like I dont know what I can even describe the gap as. I was told by my stepfathers buddy(a mechanic) that there should be like 5 or 6 one thousands of a gap around the piston and the cylinder all the way around. I am not talking a gap between rings now. the rings are tight in there. I just wasnt so sure about having any movement in the piston. I need to find the bore guage and micrometer to check this out now. I just hope that its alright, I dont feel like waiting for another piston!!

[Silverfox@C&DRacing]

Don't worry about the # on the bottom of the piston that is a manufacture # or reference not the piston size. I would get it measured to be on the safe side..

[RideRed400StYlE]

I took it back out, and put the rings in the clyinder and measured them with a feeler guage, and the bottom ring is almost to spec, but the top is way out. I think I am going to get some new rings and hone the cylinder. I am going to measure it all first to make sure though