03' 600 rmk crank seal?

[bigbadbear]

i JUST had the motor rebuilt, and had mountain toys put in new crank bearings and seals. first ride out, it starts making a grinding sound, so i mixed the gas with oil ( made sense at the time). i removed all that tainted gas, and cleaned everything i could. it runs fine now, cylinders and pistons are fine, but it back fires out of the pull start rope hole! makes no sense to me. all i can think of is crank seal. any input is greatly appreciated! thanks!

 

[s/b tech]

Would take it back to the place that put the motor together and let them have a look. Is it not covered under warranty? Sounds like something wasn't right from the get go.