Help me out with this one... I think I know but would like some backup. I just took an old 2.5 (not R) and rebuilt it. While it was out I thought I would do a Port and Polish on it. I put it back together and started it up and it idles fine, runs up to 1/3 throttle fine. Here's the kicker, after that it takes of to WOT and runs all by itself even with the carb back at idle. Its a air leak I know, but I dont know where. I sealed the carb and back plate with permatex.. it's not there.
I was playing around with this one and when I ported it I took the exhaust port lower on the bottom side. The piston doesn't uncover the bottom edge of the port but I think it's just barely covering it and it's sucking air there somehow.
What do you think guy's?