I recently went riding yesterday and when I let my dad ride my 300EX, I noticed it smoking slightly when he let off the throttle. I stopped him and informed him and he said he knew. I'm concerned about what is making it smoke. I know that is a 6 year old motor and that all it may need is an oil change, but what if it's something else? What else could it be? Please help?

 

One thing it could be is blown piston rings . Have you noticed any loss in power ? even just the slightest bit > I blew the rings in my 99' recon , I didnt notice much of a power decrease but the more i rode it the worse it got . If your bike starts smoking more then you probably have blown the rings . If you dont fix it it will cause serious trouble later on . BUT my friends 01' 300ex smokes when it gets really hot and so does my 87' 250X and every other 300EX i have seen . WAS you 300 really hot when this happend ? If so dont worry it is OK i dont know why but its fine .

 

What color was the smoke black, blue, or white? If your piston rings are worn out you will see a light shade of blue in the smoke

 

if it's after you've been riding it for a while, and the smoke is blue, then it is the rings going bad, and you wanna get that fixed as soon as possible, it could do some damage if you let it go.

if it only does it when it gets really hot, then you might want to try running a heavier weight oil 10W40 or even 20W50