valve seals

what often occurs to me if my valves seals are busted if my bike exhaust a white smoke at idling . If this happens automatically you have problem on the valve seals. But at idling and no white smoke only when reving to high rpm, pls., check your petrol. In 4 strokes for me it is the best to use gasoline color red. Hope this is useful

Knowing this is a yr old thread and the chances of the OP still being around to reply are slim.

Having said that the way to check for leaking valve/s is with a wet compression test.

Do a dry compression test (remove all plugs from all cylinders if its a multiple cylinder engine and make sure your battery is fully charged) Record the numbers. Do it 3 times to get a good average.

Then do a wet compression test. Take a oil can and squirt some oil into the cyl and crank.
Put a little oil in each time before you crank it.and record the numbers.

If the numbers still match after a wet compression test then you have a leak and most likely the valves are leaking (assuming the headgasket is not leaking)
If the numbers go up after a wet test then you have leaking rings.

The oil forms a temporary barrier around the rings to enable the rings to seal for a few cranks while doing the test.

The other way is with a leakdown test. You fill the cyl with air and moniter the pressure. You can check where the air escapes and determine what is leaking.