2011 apex mxr90

[mike#187]

hello how goes it , my son has a 2011 apex 90 and i was going to do the porting on the jug and i wanted to bump up the compression and was going to have the head machined down and i was wondering how much i can take off of the head? please help me

[force245]

You might call around to some of the engine builder and discuss, but I doubt they will share secrets. And no offense, but if you need to ask these question, you probably don't need to delve into that arena. Port timing is critical and a few degrees off came ruin a cylinder and totally destory to way the motor runs.

What I will tell you is a great piston to head clearance is .030ths with head gasket in place. From there you can set your squish band, but you cannot go to narrow or it will disturb the turbulance and the burn.

With these two adjustments that should be done to any stock motor anyway, you will pick up a lot.