OEM PISTON

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MX Quad Dad · #1 Post by **MX Quad Dad** » Sun Oct 30, 2011 2:11 pm

I have a 2000 Artic cat ZR 600 EFI. We tore it down to freshen it up. the original pistons had two small "drilled" holes at the point of the exhaust bridge in the cylinder and the new OEM pistons didnot. I know I have read stuff in the past about drilling these holes for some reason. can't remember why it was sugested and would like to know if I should worry about it

2000ex · #2 Post by **2000ex** » Sun Oct 30, 2011 2:59 pm

Gas porting. I believe it is designed to increase ring pressure

promod · #3 Post by **promod** » Sun Oct 30, 2011 3:23 pm

QUOTE (MX Quad Dad @ Oct 30 2011, 09:11 AM) <{POST_SNAPBACK}>

I have a 2000 Artic cat ZR 600 EFI. We tore it down to freshen it up. the original pistons had two small "drilled" holes at the point of the exhaust bridge in the cylinder and the new OEM pistons didnot. I know I have read stuff in the past about drilling these holes for some reason. can't remember why it was sugested and would like to know if I should worry about it

Im not sure if the AC you are talking about is 2 or 4 stroke, but with you mentioning exhaust bridge on the exhaust port in cylinder it must be a 2-stroke, holes were drilled in the pistons for the fuel/oil mix to lubricate and keep the exhaust port bridge cool (and was sometimes drilled on the intake side if the intake port was bridged) and keep the bridge from expanding in and putting pressure on the piston causing premature wear or siezure!, And in my vast experiance with two strokes if i was using other pistons that was not drilled would drill them to let them still do that job, unless i went with radical porting and removed the bridges, but you have to make sure the ports are not to big after doing that to cause ring snag in them due to piston ring locating pin location on the piston, which in that case if i was max-porting a cylinder out and removed the bridge and that was a problem i would relocate the piston ring locating pins!

MX Quad Dad · #4 Post by **MX Quad Dad** » Sun Oct 30, 2011 10:59 pm

Ok. The sled is a 2000 which had the original pistons in it (with the holes) the 99s have a differant part number for the piston (which are the same bore and stroke and seem to have a differant linner plating) but nobody stocks them so I can look at them. My son inlaw bought this sled new in 2002. my worry is I might have a 2000 with a 99 engine in it but I can't find a manufacture date on the sled. is there anyway to find out what year the engine is or is running without the whole going to hurt it?

Thanks