Valve and decompressor - 2010 Bajaj Pulsar 150 DTSi

You mean when you turn the key you hear buzzing sound but starter is not turning motor?
Sounds like automatic decompressor valve not activating on cam and starter motor cannot/will not be able to turn crank against compression. see if you can spin the motor by hand. If not you need to replace valve decompressor gear inside motor.

I presume you lined up the rocker timing before removing the shaft ? if not then the valves will be out of order for up/down

Hi Kerry,
The decompressor valve is there to make starting easier. All you need to do is to push the button in before you try to start the saw. As soon as the engine fires, the button will pop out and the saw will then operate normally.
Just remember that if you pull the saw over and it kicks, but does not start, you'll probably need to push the decompressor in again.

OHV? First try adjusting the valves too much clearance will the decompressor to not work. Now the decompressor can also fail but try the valve adjustment first.

Very can be if it is an OHV engine that either the valves are needing adjusting or the decompressor has failed.

Most 4 cycle small mower engines have decompressors to help with the starting, These are only active at start-up and does not effect normal engine compression when running.

Either the valves are out adjustment or the decompressor has failed.

Most OHV valves valve clearance open over time causing the decompression system to become in effective; however, the decopressor fails and even properly adjusted valves will still will not decompress the cylinder for starting.

I just repair a B&S 310000 series that had so much compression that the engine would even complete a cycle. After checking the valve adjustment I found that the decompressor on the cam had failed.

Check your valve adjustment first as these uses a decompressor that on the camshaft itself.

Now while checking the valve clearances as you go past TDC of the compression stroke there should a little bump on the intake valve when the decompressor is working. If this bump is not there and the valves are set correctly then the decompressor has failed and requires the cam to be replaced.

10 276781SingleCylinderOHV pdf

You likely need to get the valves adjusted,it sounds like the decompressor is not working.You need to get the compression down to 130 lbs while cranking or the starter can't overcome the compression.Try turning the motor past the compression stroke by hand and see if it will crank faster,if so then the decompressor is out of adjustment.If the decompressor is not just a lob on the valves then you need to call the repair depot for craftsman and find out what you need to do to fix the problem.If none of the above works then you may need a battery,or just clean the cables and battery posts.

Sounds to me like the decompressor is not working.You need to find out what this engine uses for a decompressor,whether it be a valve adjustment thing or a linkage thing,the dealership service manager should be able to give you some guidance.

It possibly could be the decompressor valve on the external part of the head of the mower.
it has a black tube that runs to it.
Remove the tube and the decompressor valve from the mower, put the tube back on the valve and **** on the tube and then hold your tungue over the end of the tube, the valve should pull in and stay there as long as your tongue is blocking the tube, when you remove your tongue the valve should come out if it is working properly.