300EX troubles

[DPeoples]

Need Help
riding the other day I heard alittle tapping then I shut it off. Went to start it up ran a little then boom it back fired trough the carb tried to restart it again boom through the carb again this time it popped the carb off. I set the valves but it is still doing this back firing through the carb. I need Help. Does anyone know how to fix it? dpff447@yahoo.com

[ghak99]

It almost sounds like your timing chain could have stretched and jumped a tooth or two.

[400exdad]

Yep, definately sounds like it jumped time. Take the valve caps off and watch the cam as you turn it over. I bet the rockers will still be on lobe when the timing mark lines up.... both times. Remember, to watch the intake valves open and close and on the next timing mark on the flywheel, it all valves should be closed... and the rockers should have your clearance.

[DPeoples]

Should I replace the timing chain or is this something that happens often? This is my first 4 wheeler.