How to set valves

To adjust your valves you will need a few standard tools and most importantly a set of feeler gauges. You can buy these at any automotive store. The first step is removing the tank and valve cover to gain access to the valve train. You will see both the intake and exhaust cams plus the tops of the valves. This is where you will be measuring with the feeler gauge. The next thing would be to rotate the motor to top dead center. You will need to remove both inspection covers that are on the side of your ignition cover. This will give you access to the timing marks and to the bolt that allows you to turn the motor over.

Check in your manual as to what direction to turn the motor over. You do not want to turn the motor over in the wrong direction. Turn the motor over looking into the inspection (top) hole. You will notice a mark on the fly wheel. When you see this mark come around, look up at the cams. There should be two punch marks on the cam gears that line up with the gasket surface towards the outside of the head. At this point you should be at top dead center compression. Check the lobes of the cam, they should not be touching the valve buckets. If they are touching the valve buckets, this means that you are 180 degrees out of time. Rotate the motor 180 degrees and then start to measure.

After you measure the clearance between the cam lobe and the valve bucket, you will want to write that down. You will then need to check your numbers against the spec's provided in your service manual. If you are outside the specified range, you will need to remove your cams and replace the shims. There should be a chart in your manual that will help you to decide what shims you will need to bring you within the safe range. When dealing with the KXF250 or the RMZ 250, you want to make sure you use the correct shims. There are two types that will fit these bikes, but only one is the correct shim. Shims come both forged and sintered. They look the same until you put them under a magnifying glass, then the difference is very clear. The forged shims have a smooth surface, while the sintered shims have very small cavities. Using the sintered shims will prematurely wear the coating off of the valve stem. This will shorten valve life and cause the valves to go out of adjustment sooner.

Now, after replacing the shims, all that is left is to reassemble your machine. Pay closer attention to the instructions in your owners manual. Always double check your cam timing with what is recommended in the manual. Do not start your bike without turning the motor over by hand first. If you feel it is unusually hard to turn over or it will not turn over, you probably are off on your cam timing. Once again, do not try and start the bike. Go back and retime your cams.