My Prairie 300 has a smooth idle, but starts running very rough at approx 15mph.

It does this every year after I start it from the winter.

I am tired of taking it to service, because the service dept never really gets it running correcly anyway.

Can someone point me in a direction?

Thanks,

Campbell  

I'm new to this forum, and my main forte is working on 2 wheelers mostly but I've been repairing bikes for over 30 years. Now to respond to your question. It sounds as if your gasoline is breaking down and gumming up your carburator during the winter. I would take off the float bowl and blow it out without dislodging the float pin or needle valve.Next use some carb cleaner on the main body and blow it out. A computer can of compressed air Should suffice. Next winter when you store the ATV use a Gasoline preserver that is sold at your local car parts shop and don't forget to disconnect one battery terminal so it doesn't drain the battery. Its also a good idea to get the model # of your carb, probably a mikuni,could be keihan, and get a rebuild kit that will have all the needed parts for any worn parts that will need replacing.(o-rings,needle valve,etc...). A manual won't hurt either. Also take the cover plate off your magneto,points,whatever,and see if that area is dirty and needs to be cleaned also.Check plug for carbon buldup also and clean or replace if necessary.