600 ho mod need help clutching

I bought judnicks brothers mod motor and it runs unbelievable but I didn't know where to start with clutching so the biggest weights I had were 53h almond red primary secondary is red with black stripe with the stock 440 helix, I put 21 top 41 bottom gears in it that he gave me at the same time. I am not sure as to how high this thing is supposed to rev but trying to hold on I have at least seen 8500 from it. I have not really been able to ride it much yet but any help is greatly appreciated especially since i have not found very much info for a mod. I plan on racing hillx with it mostly with a few snox races. Thanks in advance

I dont know what the rpm range is supposed to be. I was told to run atleast 114 but if possible 116 so I run 116. I do have polaris race pipes on it. It seems to pull hard from the start but through the shift seems to lay over or feel kinda dead put then pulls hard again but I really havent got to ride it much in decent snow. I dont know what a mod even came with from the factory so I dont know if I am even close