98 scrambler 400 engine build

[97polaris500]

i just recently picked up a 98 polaris scrambler 400 and it had no compression so i tore the motor down and noticed the exhaust side of the piston was burnt from the top to the upper ring and the side skirt was all scraped up! now one question i have is what direction is the arrow on the piston sapose to be facing or what way are the ports on the piston facing? cause the piston and gaskets were all pretty much brand new so they must of done something wrong when they rebuilt it! i did notice they put the c-clips in wrong. another thing i noticed was they installed a 38mm flat slide mikuni tm carb and the exhaust pipe is not stock! the carb was completely gummed up when i got it! does any one know where to get a rebuild kit for it?? i am sending the cylinder to ritters cycles and im going to have them port the intake and exhaust, bore the cylinder to the next size up, cylinder head mod, and a new silencer! now a couple more questions sorry, what size jetting should i get or am i going to have to experiment, and what about clutch! the bike is going to be on 28 inch mud zillas or bigger if i buy new ones and its going to be snorkled

[RENOBADBOY]

2stroke the arrow gos towards the exhaust. Sounds like it seized up or came close. I replaced my CDI box with an aftermarket one on e bay that had more timing in it plus it eliminated the rev limiter' Woke up my ol' 300.