I have a 1986 yamaha 540 srv snomombile and when i throtle it up it bogs out and pops like a backfire do you have a suggestion on what is causing this and how to correct it?

You should purchase a gasket and seal set, pull your motor out of the sled, disassemble the motor, and replace all the gaskets and seals. You can purchase a piston kit on line that should come with pistons , rings , gaskets , and seals.The main problem you are having is an air leak on one or both of the crank end seals. Usually the clutch side seal leaks first. If you continue to drive you will probably score one or both of the cylinders.When you have the motor apart clean your carburetors and replace your spark plug caps. NGK has new plug caps for about $5 each. If your cylinders look good i would consider doing a light hone job and ring replacement. Again if you just buy new aftermarket seals pistons and gaskets you should be able to do a complete rebuild for about $150. Then your engine will be good for another 25 years. If you are limited on funds Just replace the crank seals , clean the carburetors, and put on new NGK plug caps (about $30).