Hi, new here, can anyone help? I've got a problem with my 2001 ttr250!
I hadn't used it for nearly a year, but started & ran it regularly though..... I realised over the last few times that it ran perfectly on the choke but when I switched off the choke it had started searching for an idle, popping & when the revs really troughed, it would backfire to a greater or lesser extent & eventually backfire in a big way & stop. When I say backfire..... loudly, through the carb & air box leaving a smoky haze around the carb area. Bringing up the revs, upping the idle screw, working the throttle would keep it going but as soon as it was left alone it would start searching again & eventually trough, backfire & stop!
Riding it is fine, the only change is that it has become hesitant at low revs, not wanting to pick up. There now appears to be a bit of a black, sooty residue in the carb intake boot & snorkel!
New fuel, no change.
Obvious next step was carb rebuild...... no change.
Welcome to the forum!
Always suspect the carb first! The pilot circuit is very fine (not just the jet, but the ducts as well) and easily plugged by dirt or fuel residue. Sounds a bit like lean running on the pilot circuit to me because you say it's ok with the choke out - ie getting the extra fuel it needs.
Alternatively, timing chain jumped a tooth?