I have a 1977 Yamaha DT 100cc and for some reason it wont run without the choke on (when the engine is warm). As soon as you give it about a centimetre of choke, it will run fine. But as soon as you give it no choke at all, in about 3 seconds the engine will bog and stall, then will not start again not start unless you give it some choke. I have cleaned the carb, changed the gas, put gas line antifreeze in the gas, replaced the air filter, fuel filter, did a compression test (which passed), adjusted the idle, tried every different spot on the needle, tried new spark plugs, but nothing works. If I do run it with the choke on, it fouls plugs and overheats. It takes mixed fuel, so there is no oil pump. Any ideas what this could be caused by?
Thanks