so far mines run pretty good a 29cc T1000 i got from king motors. as mentioned earlier, my starter also stripped out after 2 tanks of gas, ordered a new starter that was made a little different on underside, i had the shroud or collar surrounding the engaging part, solved the issue, so far that ones working great.
only upgrade i got that didnt work was a enclosed clutch carrier, the one received was not the one pictured, to which i have found a very close match for that pictured part i thot i was getting, a turtle racing cover, only differences were a few holes drilled here and there on places, thats it,
this was one in auction pic:

this is one i got:
nothing alike, and bearings were misaligned when installed, had to force bell shaft thru, and was tight to turn. so had to end up sending it back, and got a metal version of the stock plastic 3 point connection carrier, its working fantastic so far. everything else i got including the truck itself from same seller has been great, not sure what happened on this paticular item, but i don't think its his fault, IMHO
UPDATE:::: after talking it over, i think me and the seller have both agreed that i just got ahold of a badly machined part. i talked to him bout the old one, which apparently the one i got was the NEW style, he held a old style for me and i bought that from him, i put in the bearings other day, and everythings lined up as it should be, i like the old style lots better than that new style.
this is the turtle racing one pulled right from thier site,
see the remarkable resemblance between the auction pic and this one? i think the one i got was just a poorly machined one, if i had recieved the one in auction pic, im positive it would of been perfect, cause i think the auction pic is a TR carrier modified with some added holes for weight reduction and maybe heat tranfer.