Lost manual when should valves be adjusted 2006 C5OT 14000 miles?

Tappets......... perhaps is what your friend said. The tappets are part of the engine inlet and exhaust valve set up. Most tappets are self adjusting in modern motors, (Hydraulic).
The old fashioned tappets are manually adjusted during regular car servicing. This happens at set intervals, for instance every 20,000 miles.
Inlet valves allow air and fuel into the engine and exhaust valves let the burnt fuel and air out.
Tappets are fitted between the inlet and exhaust valves, they ensure that the valves open on time and more importantly close properly. If the tappet happened to be badly adjusted and did not let the valve close properly then damage to the valve and cylinder head can happen by burning.
If you have a significant power loss I would be surprised to find that the just tappets/valves were to blame.

change the pcv valve this maybe the cause of it burning oil.causing too much pressure in the crankcase system

All the parts in your engine are wearing in. Part of the 600 mile check up involves adjusting the valves and the cam chain tensioner (if it is not self adjusting). Chances are the valves are wearing in, the gap is too wide, and just need to be adjusted back to the correct clearance. Worst case scenario the cam chain tensioner has failed. http://www.kawasakiforums.com/forum/general-tech-9/klx-250s-2006-loud-clicking-sound-not-valve-33671/

Hello...from your comment it sounds like your bike needs a valve adjustment. The "hollow" sound in the exhaust and the powerband loss is usually a good indication of this. Have you had them adjusted lately? This first adjustment should be done at 5000 miles and then every 7500 miles there after.
The settings are:
Intake .003 - .005
Exhaust .007 - .009
Always set valves on a COLD engine.

I hope this helps...good luck with your bike.

The valve clearance is automatically adjusted be the hydraulic valve lifter. However Yamaha say there are times when the valve clearance needs to be adjusted manually. Basically to balance a pair of valves if they become misaligned (pretty dam rare) as they are operated by the one lifter. (eg Inlet pair has one hydraulic lifter and the Exhaust pair has one hydraulic lifter)

The recommend service / checking interval is 20,000 kms. (12,000miles approx) according to the manual.

I have 15800 miles on my 2008 and after speaking with a Yamaha service technician, he hasn't had one in yet that has required adjusting when he has carried out the 20,000km service. Infact he has had to adjust one as of yet even at 40,000kms.

It is a bit of a pain to do, as a lot of stuff has to be removed and the covers are a little tricky to get off.

Me, I am not going to bother until 24,000miles, as long as you change the oil and filter every 5000 miles my Yamaha guy recon it will be OK.

If you are going to do it yourself, you will need a manual as only one value has an adjuster and the other is a slipper, so they are not as easy to adjust as a pair of standard valves.

Sounds about right. Most bilkes need the valves adjusted every 3-4000 miles. 3 hours also sounds right and you can check around to get a better hourly shop rate.

1st valve adjust at 1000 miles, then every 15k is good...Good Luck to you friend....tim

http://www.carlsalter.com/motorcycle-manuals.asp

right there you will find a free pdf service manual. all you need to know......

vans speed sensor went bad.

they are at 4000 miles, and that's for all service.