We bought this lawn tractor two years ago. Now all of the sudden it will not start all the time. It will lock up on crank and then run. Then it will vibrate real bad at lower idle. The company we bought it from, says the did a lot of work to it and made some improvements but not quite fixed. It also backfires thru the carb when starting, after it locks up. If anyone has suggestions on what may be the problem, comment back. Oh and it has a 21hp motor. Thank you in advance
