dang Bryan; sorry for that grenade. i found a 655 that i am re-ringing. you know the 650 with an aluminum filter cover. anyway, good luck buddy.

What a bummer. Damn.

also a leak in a crankseal or gasket will let it go lean , plus your carb is too small need a dbbl pumper carb

they sometimes bust up top where the needle bearings that are made into each side of the piston the two sets of needles get stuck and if you do not clean them up often they quit turning then ya get flatspots then heat BANK ! caster oil is bad on the needles you gotta clean em DBN

101 blocks are geting hard to find & expencive !/ allways do a pressure test on the crankcase terry ives sells parts to all the VKA racers

the flex is too short on your pipe needs to be 91/4 inches from ex. side of piston face to the 1st cone if too short it will run hot ! / terry ives sells parts for many macs even hi per rods for the mc101 rod bolts need replaced on every teardown & rod needles too

a wrist pin puller tool it pulls them and press them in too rods are shotpeened from faxctory IVES sells a HI po rod

is the piston burnt on top ?

rod bolts need to be replaced every rebuild & rod needles too i am not tryin to be a smart ass just passin on knolidge from years of raceing macs new pistons cost $85 ! rod bolts are $1 lets see the piston ??? i have sets of new ring sets for sale & seed cages too

Over Tightened Bolt necked it weakened it bang soon as you gave it wellie no more bolt