I've been building up my mini bike ('88 ZB50). I've upgraded it with an 88cc piston and big valve head. I've got it to run but I can't get it to idle. I have to goose the throttle to keep it running. The fuel screw is at the stock position (1 & 3/8 turns out), the needle clip was in the middle position. Idle screw seems to have no effect. I lowered the needle clip from the middle to the second lowest position (the needle has 5 positions). It seemed to want to idle a little more but would still stall. Lowered the needle clip to the lowest position and the engine would idle but at like 6000rpm. Turning the idle and fuel screw had no effect. I put the clip back to the 2nd lowest position. Anyone have an idea where I should look? Air intake leak?
BTW: It runs pretty darn good when it's got revs but it won't idle. ugh.