Valve Seat Servicing - BRP Johnson 4HP Service Manual

POWERHEAD
VALVE / VALVE GUIDE

Valve Seat Servicing

If the valve seat contact width is out of the specification,
reface the valve seat as follows:
Valve seat angle: IN 15°, 45°
 Valve seat cutter 45° (NEWAY122)
Valve seat cutter 15° (NEWAY121)
Handle adaptor (N-503-1)
Solid pilot (N-100-5.52)
Handle (N-505)
NOTE:
Turn the cutter clockwise, never counterclockwise.
1. Remove all carbon from the valve and the valve seat.
2. Using the 45° angle cutter, reface the valve seat.
3. Check the valve seat contact width A.
See the "Valve seat contact width" section on page 6-15.
4. If the width A is too high (or wide), reface the valve seat
using the 15° angle cutter.
If the width A is too low (or narrow), reface the valve seat
using the 45° angle cutter.
5. Clean up any burrs using the 45° angle cutter very lightly.
Grind the seat areas minimally only.
Do not grind more than necessary.
6. Recheck the valve seat contact width A.
Do not use lapping compound after the final cut is made.
The finished valve seat should have a velvety smooth
finish and not a highly polished or shiny finish. This will
provide a soft surface for the final seating of the valve
which will occur during the first few seconds of engine
operation.
6-16
EX 15°, 45°
IN. EX
Valve seat
• Too high (wide)
• Too low (narrow)