Cam shaf wearing groves

change the spark plug or there in good condition.

The EGR Valve is located right on the back of the intake manifold on the left side. Take the cover off the top off the intake manifold and you will see groves under it inside these groves are a couple of hole about 5/16 diameter. clean the holes and groves , and your back in business. Note somtimes this area gets so gummed up you may not see the groves , make sure you clean out the grooves and the holes . ----------- This should help.Thanks.Helpmech.

Clogged PCV Valve
The main purpose of the PCV (positive crankcase ventilation) valve is to recirculate blow-by gases back from the crankcase area through the engine to consume unburned hydrocarbons. Blow by is a mixture of air, gasoline and combustion gases forced past the rings on the combustion stroke. The PCV system usually has a tube leading from the crankcase to the carburetor or intake manifold. Vacuum within the engine intake manifold pulls blow by gases out of the crankcase into the combustion chamber along with the regular intake of air and fuel.
Worn Piston Ring Grooves
For piston rings to form a good seal, the sides of the ring grooves must be true and flat - not flared or shouldered - and the rings must have the correct side clearance in the grooves. Normally, automotive ring groove side clearance should not exceed .002-.004. As the pistons move up and down, the rings must seat on the sides of the grooves in very much the same way that valves must seat to prevent leakage. New rings in tapered or irregular grooves will not seal properly and, consequently, oil will pass around behind the rings into the combustion chamber. Worn grooves are usually flared or tapered causing increased side clearances which permit more than the normal amount of oil to pass the rings into the combustion chamber. Excessive side clearances also create a pounding effect by the rings on the sides of the piston grooves. This promotes piston groove wear and, if the condition is not corrected, breakage of rings lands may occur.
Cracked or Broken Ring Lands
Cracked or broken ring lands prevent the rings from seating completely on their sides and cause oil pumping by a process similar to that described in #7. In addition to this, they also lead to serious damage to the cylinders as well as complete destruction of the pistons and rings. Cracked or broken ring lands cannot be corrected by any means other than piston replacement and this should be done as soon as there is the slightest indication of a crack.
Worn Valve Stems and Guides
When wear has taken place on valve stems and valve guides, the vacuum in the intake manifold will draw oil and oil vapor between the intake valve stems and guides, into the intake manifold and then into the cylinder where it will be burned. If this condition is not corrected when new piston rings are installed, an engine is likely to use more oil than it did before because the new piston rings will increase the vacuum in the intake manifold. When gum or deposits on the valve stems are removed - a procedure recommended when overhauling an engine - the seal previously formed will be removed and leakage will be more pronounced. This is particularly true on overhead valve engines where loss of oil may occur on the exhaust valves as well as on the intake valves. High oil consumption caused by too much valve guide clearance can frequently be cured by reaming or nerraling the valve stem. In some cases new valves may also be required. Use of a permanently bonded valve stem seal will give added insurance against oil leakage on complete engine overhauls or on valve jobs. Large Oil Leaks Leaking valve cover gaskets, leaking crankshaft front and rear seals.

you may expect no lower than 10 hours because you have to remove motor and dissasembled and you may expect to reshim a valve or two that is too tight at the same time.....we rebuilt a kx 250f 2008 last week and rebuilt the crankshaft and change valve guide and reangle valve seat for 12 hours r&r.....

Make sure the carb is clean as the fuel gets old sitting in the bowl, and i have heard of a few of these,doing the same that need the valves adjusted, just dont ask how this can happen while it it sitting in the shed

Assuming the bike idles smoothly and is not smoking you can pretty well rule out bad valves and piston rings. If the air filter is clean then intake should be okay. Are the valves set properly? Is the decompression lever and valve working properly? I assume there is not mud plugging up the pipe. That pretty much leaves the muffler on the right side having an internal collapse and is restricting the flow of exhaust gases. Remove the mufflers and see if the pressures are equal at the head. If the problem is still there then have the shop do a compression check. It is possible a ring has broken or is frozen in the ring groove. This would let some compression into the gear box and account for the lower exhaust pressure. I hope this helps.

You need to remove the valve cover and rotate the crank shaft to TDC then with a feeler gauge you check the clearance between the cam lobe and lifter bucket. There are 3 on intake cam and 2 on the exhaust. The clearance will most likely tighten as the valve seats and valve wear in. If the valve clearance gets too tight they will hang open and not seal for proper combustion. Valve clearance for my 2002 YZ426 are intake=0.10-0.15 mm (0.0039-0.0059 in) exhaust=0.20-0.25 mm (0.0079-0.0098 in) the 450 should be the same or very close

try this one buddy get back to me if not.

http://cgi.ebay.com/ebaymotors/KAWASAKI-KX250F-CYLINDER-HEAD-KXF250-CAMSHAFT-RMZ250-_W0QQitemZ250498256399QQcmdZViewItemQQimsxZ20090914?IMSfp=TL0909141610003r32064

sounds right, but shims dont really wear the valve sits in or the lobe wears, hence the need for re-shimming

Chances are when the OHC was installed it was one tooth off on the timing. You have spark and gas and the bike is a single cylinder so that is what I would check. Slack in the chain tensioner is what usually creates the problem. All slack should be at the back side of the cylinder.