Just bought a 74 DT175 soaked the carbs, sparkling clean now. Replaced spark plug and fuel line, coated tank, new oil. Getting good spark, fuel into carb, oil to cylinder from pump, can hear throttle work properly, set air mix screw at 2 turns out and idle screw at 3 turns out.

With choke out starts right up but idles at 8000 rpm. Put choke in immediately dies. No air filter in, I don't know if that would cause any of this. Any help would be great. Thanks

Problem solved. Was leak at crankcase to carb joint.

Hi, could you explain a bit further regarding your link from crank case to carb joint? I have a 1975 XS500 with a sinular problem. I cleaned the carbs put them back on. The bike starts, is better than when I got it but the idle won't stay steady. I'll get the fast idle scew set at about 1500 and it will behave somewhat but when I rev the engine it takes a long time for the rpms to come back down. Also I have to have the choke on a bit for it to stay running or it dies.

Hi, could you explain a bit further regarding your link from crank case to carb joint? I have a 1975 XS500 with a sinular problem. I cleaned the carbs put them back on. The bike starts, is better than when I got it but the idle won't stay steady. I'll get the fast idle scew set at about 1500 and it will behave somewhat but when I rev the engine it takes a long time for the rpms to come back down. Also I have to have the choke on a bit for it to stay running or it dies.

Old thread I realize, but in case... Sounds like you definitely have an air leak somewhere, Start it up, then take some carb cleaner (the spray kind) and gently spray it around every joint and connection on the carb. You should hear a change in idle at some point. Go slow and careful, a big cloud of spray wont really tell you where the leak is.

Mike