I just bought a used 660r and i took off the aftermarket slip on muffler (too loud for in town)I bought a stock muffler with spark arrestor in it,It still runs good but should i mess with the jetting anyway? I dont know if they have been changed or not.

 

I would pull the spark plug and check it out. It might be running rich now. If its really black then its too rich. Look for black smoke coming out of the pipe also.

 

If the plug looks ok and it runs good then your good to go!

 

Thanks, I will check it out this weekend,To rich is better than to lean!!!

 

Thats for sure!!