Disassembly
Loosen the camshaft sprocket bolt while holding the shaft from turning with a wrench.
Remove the camshaft sprocket.
Remove the oil lines from the rocker arms.
Remove the camshaft thrust washer.
Remove the camshaft.
Release the crackers from the valves by compressing the valve springs with a valve spring compressor.
Remove the springs with plates and valve springs, put in order.
Take out the valves.
Remove the valve guide bushings and spring washers.
Press out the camshaft seal.
Wash and clean the removed parts and cylinder head.
Check the valve seat faces for pitting, corrosion, and damage. Minor damage can be repaired by grinding, removing as little metal as possible. After grinding, thoroughly rinse the seats and cylinder head passages and blow them out with compressed air. Remove carbon deposits from valves. Check for deformation of the valve stem and cracks in the poppet. Check the condition of the valve face. In case of minor damage, it can be sanded, maintaining the required chamfer angle. Check clearance between guide bushings and valve stems.
If the gap between the guide sleeve and the valve is increased, press out the valve guide using a Mazda 49 0249 010A drift towards the upper plane of the cylinder head.
Press in a new guide bushing with a circlip fitted using the same Mazda 49 0249 010A punch until it rests against the cylinder head body.
Check for warping of the cylinder head mating surface.
Assembly
Press the valve stem seals onto the valve guides.
Insert the valves into the guide bushings.
Install support washers, springs, spring plates. By compressing the springs with a special tool, install the valve cotters.
Lubricate the camshaft with engine oil and put it in place.
Install the camshaft thrust washer.
Press a new oil seal onto the front end of the camshaft, after lubricating it with engine oil.
Install the rocker arm lubrication lines.
Insert the key into the camshaft socket and put the toothed pulley on the shaft.
After blocking the camshaft with a wrench, tighten the toothed pulley mounting bolt.
Turn the camshaft pulley until the alignment marks of the timing mechanism are aligned.