Thread: 1970 70h stumble backfire

before i check any more with this problem i need some experenced ideas .my 70 was running good i thought if it was going to be sitting for a while this winter i would put some stable in the gas after doing this i rode it some,it started running rough ,thought maybe i had used to much stable,so i drained all the fuel and added fresh it still ran the same . i took the carb apart and soaked it good,used wire and cleaned all the passages it has anew needle jet set and all other parts new. with the air screw set at about one and one eight turns out it starts and idles fine with a slow throttle opening i get no stumble or back fire ,but if i open the throttle normally i get backfire and hesitation sobad it tries to close the choke if ican get the rpms up it levels out ive checked for intake leaks and tightened the head bolts something tells me its not the carb but may be timing ,points gap or spark advance

try throwing a new spark plug in.

I found my problem the points gap had slipped almost closed , i guess the screw loosened. back to normal now.