Here's the story, it's kinda long. I've had a '71 Trail 70 4 speed (CT70H) for years now that hada bent intake valve. I finally got it back together a few months ago and it the process ported the head up real nice. After getting it back together it ran so lean that I had to run it with the choke all the way on, otherwise it would die.
I bought a 20mm carb for it which is typically used in the 88cc conversions. For the most part it runs great now. It pulls hard all the way through every gear. I can even get a 2nd gear wheelie and pull the front wheel up for a bit in third. I stepped the main jet down to 82 and it seemed good except for a bog at forst when I hit the throttle hard. It went away if I turned the air / fuel screw in all the way (rich), however my idle screw is almost all the way out (lean) otherwise it idles way too high.
I got it up to operating temp and took it full throttle through the gears and immediately shut it down. I took the plug out and it was nice and bronze. I then did the same thing at 1/2 throttle and the plug was white. I richened up the metering rod and now that looks good. I was able to lean out the A/F screw a turn. At idle the screw is still way out and the plug turns black.
Should I pull the pilot jet and replace it with the stocker from my old carb, or should I see what is in there and just step down a couple sizes. What else, if anything should I try?
I bought a 20mm carb for it which is typically used in the 88cc conversions. For the most part it runs great now. It pulls hard all the way through every gear. I can even get a 2nd gear wheelie and pull the front wheel up for a bit in third. I stepped the main jet down to 82 and it seemed good except for a bog at forst when I hit the throttle hard. It went away if I turned the air / fuel screw in all the way (rich), however my idle screw is almost all the way out (lean) otherwise it idles way too high.
I got it up to operating temp and took it full throttle through the gears and immediately shut it down. I took the plug out and it was nice and bronze. I then did the same thing at 1/2 throttle and the plug was white. I richened up the metering rod and now that looks good. I was able to lean out the A/F screw a turn. At idle the screw is still way out and the plug turns black.
Should I pull the pilot jet and replace it with the stocker from my old carb, or should I see what is in there and just step down a couple sizes. What else, if anything should I try?
