My dad has a 1991 Indy 400. It seems to bog down when under throttle. But this problem is not consistent it comes and goes. When you go hard on the throttle off the start it bogs down, come off the throttle it is fine. Any ideas? FYI it seems to burn some blue smoke every now and then as though there were unburnt fuel. Any info would be much appreciated.

have u cleaned the carbs? if so the air screw should only be 1 3/4 turns, also check the chokes. I owned one and they r a great machine so give that a try. Hope it helps

I agree - WL.

sounds like your running too rich. Just a idea to ponder on....