Who can give me a nice easy clear explanation of a valve adjustment;
How its done
Why it must be done
The cost of doing this via bike shop
Consequences of not adjusting them
My bike has 44k miles and it hasnt been done
Valve clearances can change over time due to valve seat wear, metal creep, etc.
Valve clearances can get tight or loose depending on the circumstances.
The effect of incorrect valve tolerances can vary depending on the amount.
Minimally, changing valve clearances can alter intake or exhaust timing and duration slightly.
To a greater degree, too tight a clearance can prevent proper valve seating and loss of compression, and possible burnt exhaust valves due to to combustion gases passing past the valve head during ignition phase.
Too loose a clearance and damage to the cam lobe and bucket can result.
The valves are actuated by an overhead cam actuating a bucket tappet.
A shim is placed between the valve stem and the underside of the bucket to adjust clearance.
A measurement is made of the clearance between the cam lobe heel and the bucket face with the cam at it's specified alignment mark.
Each shim has a marking indicating it's thickness in millimeters.
A calculation is done to determine the next thinner or thicker shim required to correct the difference.
To replace the shims, the engine is rotated to a cylinders timing marks with both cams lobs up and cams timing marks level with the cylinder head.
The cam mount caps are removed, the cams removed and the shims swapped.
The the cams installed aligned with timing marks, then the cam mount caps installed and torqued.
The clearances are rechecked and if ok, proceed to the next cylinder.
All this is done according to the service manual procedures.
One very important thing to note is, the cam mount caps have arrows and mark indicating exhaust or intake cam, and both point to the intake side of the engine. Do not mix the caps or journal damage will result.
It's also best to start with the front cylinder since it's only a 270 degree (3/4 turn) rotation to the rear cylinder.
The cost can vary depending on which shop does the work.
I do my own, so time and labor don't count.
The valves should be checked every 16,000 miles.
Often they don't need re-shimming, but at 44,000 miles I suggest you do check the clearances.