Valves, valve seats and guides — inspection and repair

Check the valve discs (especially graduation), whether they are burned and there is no pitting on them. Inspect the saddles at the same time. If the damage is minor, the seats and valves can be lapped together using first a coarse and then a finer grinding paste. You can first clean off the deposits with sandpaper.



If the pitting is severe, the seats can be reground for new valves. If the seats are very badly damaged, the seat inserts must be reworked or replaced. However, valves are much more likely to be damaged than seats. Therefore, they are polished under saddles.

Install the valve in the guide sleeve and press the valve disc against the seat.

Measure from saddle seat (dishes) valve springs to the end of the valve stem

If the measured value exceeds the required value, then replace the valve seat. For this:

• Drill out the valve seat, leaving the seat walls 0.5-1.0 mm thick.

• Press out the valve seat.
• Machine the seat to fit an oversize saddle.

• After heating the cylinder head to 250°C or after cooling the seats, press the seats into the cylinder head.
• Adjust the valve seat to the required dimensions.