I have a to 20 that wont start i converted it over to 12v and wouldnt start. changed the plugs and started right up i didnt run it for more then a minute though. I started it up later and started great used it to haul some logs around turned it off and then wouldnt start. I changed the points the coil and distributor cap. It acted like it wanted to start but now it is acting even worse when i dont turn the key it turns over great but as soon as i turn the key it becomes very hard to turn over and there is what seems like back pressure coming out of the exhaust and the air filter. I am at a complete loss