I currently have a blown .080 over HPD race motor in my 97' Sport and the next logical step would be the 86.5mm big bore kit. Ritter is, as I post, boring for a big bore piston and rebuilding the bottom end. Do any of you fellow Polaris riders have the Big Bore Piston in your 400 Scrambler or Sports? If so, how do you like it? Do you think a reed spacer would help performance? Any information or insight would be appreciated.

Jay

 

i've tried the .080 over wiseco piston last year and was great and loved it very much,
add more torque hp and throttle response as well,now i'm thinking the
aaen 470 big bore kit for next season,this kit will rip!
the reed spacer is a MUST for big bore mods,presently i run a stock bore and it pretty boring when you thought about it... and i have the reed spacer anyway,but it seem that you lost some top end with the stock bore,a lot better with big kit...

 

I wish the AAEN 470 kit really was a 470 kit.

 

pudjumper,

You could always have the cylinder resleeved. I too have heard that you lose top end with the "big bore" kits. It makes sense to me. If you look at the ports you will see that they are angled up. when you bore the cylinder, you actually lower the ports giving you more low end, but lose top end due to the higher comperssion.

 

yeah,the aaen 470 big bore kit is REALLY a custom built kit,the cylinder is resleeved to accept a 90 mm piston,transfer passage are welded,and a monster reed box (like snowmobile)is installed,and like aaen tell in their new 2002 catalog,the cylinder is radically ported...
i'm sure this kit have all the bottom end and top end power this machine can do,their 440 kit sound cool too.