MR KNOW IT ALL

SELF DESTRUCT MODE
I just got back from my second tour of duty in Afghanistan. My 2004 Suzuki RM-Z250 seemed to age considerably while I was gone. I don’t know how a motorcycle can get more worn out without being ridden. One of the problems is that it smokes bad. Where do I start to know what the problem is?
Manny Torres

My instinctive solution involves waterboards and enhanced interrogation of anyone with a key to the garage. Someone will sing. But your problem probably doesn’t involve any misbehavior or covert riding activity. Motorcycles don’t have to be used to feel the effects of age. Your investigation should start with the smoke. What color is it? What does it smell like? If it’s white smoke, your motor is burning coolant. If it’s light blue, it’s burning oil and if it’s black it means it’s burning excess fuel. If it is a coolant leak check your gaskets, o-rings, cylinder and head for wear and warpage. All of those things deteriorate with age. If it it’s oil check your piston, rings, valves and seals for wear. If it’s burning excess fuel check your carbs jetting and function.

MYSTERY SCREWS
I have a 2010 CRF250R. I love, but I think the suspension could be better. There are two screws on the top of the forks. My friend says to remove them only when I take apart the forks. What is their purpose and which one goes where?
Mike Bixler

Here’s a list of good sources of information about your bike: Your owner’s manual. Your Honda dealer. Me.
      Here’s a list of bad sources of information: Your friend. He seems to be suffering from ask-me-anything syndrome, which usually comes hand-in-hand with a fear of the words “I don’t know.” Never believe him again, even if he sings “happy birthday.” I am giving you the benefit of the doubt and assuming that you aren’t referring to the compression damper adjusters. The two screws are both air bleed screws. These are used to release air trapped in the fork, which can result in a higher effective spring rate. The silver screw is long and the gold screw is short. The long screw won’t fit in the short hole so you can’t mix them up. Your friend, on the other hand, was born with his screws mixed up.

DOT ROT
I recently purchased a tire for my dual-sport bike on line. The price was good, but now I’m worried that it’s a factory second or a reject. There’s a white dot painted on the side of the tire. I’ve seen this before, but I don’t know what it means. Are defective tires safe?
Morgan Corning

The only defective parts here are in your head. The white dot doesn’t indicate a reject or factory second. The dots are marked on your tires to indicate the lightest point on your tire. It’s a common practice in the automotive and street-bike world, although rarely seen on full knobbies. Some manufacturers mount the dot directly above the valve stem or rim lock to balance the wheel better.