my 78 yamaha dt125 currently is not running it will run for a few seconds it makes a sucking noise from the exhaust when i kickstart it or try to push start it. i have replaced the piston rings vlave reeds pulled the engine apart to replace the crankshaft seals and there was nothing wrong with them i just got a new coil and i am going to install it and see if that helps. if anybody has any info please help thanks alot logan.