90 yz 490 questions

[laynbodys-10z]

i rebuilt this bike from the ground up this past fall, and it ran like a monster..well to make a long story short i took the cylinder to a local cycle shop and had them mic the cylinder and he said i needed a 88mm pisston which is 1mm over for my bike. well once the rust was cleaned out the cylinder the piston would slide right through with already to much clearence..well they cleaned it up best they could and i went ahead and put the motor together knowing the top end wasnt going to last to long. it lasted about 3 months before it lost compression and started to die down..anyway here the question. i just got my motor back together last night, its now 2mm over which is as far as i can go before resleeve, and now i'm getting the dreeded 490 pinging. before it wasnt really doing it. i went from a stock 40mm to a 38mm carb from a older 490, switched from the 420 main to a 390 main and was using 50:1 bel ray mc1, with a br7es plug.since this last rebuild i'm running the mc1 at 32:1. do you guys think i need to go through the carb again to try and get rid of the ping and also its wetfouling the plug..also i put a fmf fatty and powercore silencer on it probally 2 weeks before it died. also i'm in NC which is pretty close to sea level where i'm at

 

[laynbodys-10z]

i believe i got it worked out now, went from the 390 back to a 420main. moved the c clip to the second notch with the hotter plug using 32:1 maxium 927..its back to pulling the front wheel up in 5th gear :ride:

 

[2strokerfun]

Well, I was going to suggest what you already did. Why did you go to the smaller carb??