Hercules — Valve Grinding
Repair & overhaul · valves
From a Hercules owner's manual — check it applies to your exact model before use.
Before you start
- It is imperative that the valves be assembled in the same seats to which they were ground.
Procedure
- Inspect the valve guides for excessive wear; renew before work on the valve seats.
- Drive out the guides with a drift; drive in new guides to the same depth location; ream to size on the inside diameter.
- Refinish the valve seats with a vibrating angle grinder type reseating tool; exhaust seats on a 45 degree angle.
- Inspect and reface or replace valves as necessary.
- Obtain a light coil spring; lubricate the valve stem and apply grinding compound on the valve face.
- Insert the valve in the guide and rotate back and forth about a quarter of a turn, pressing firmly.
- Rotate the valve 15 or 20 degrees and repeat the grinding process.
- Apply a thin coating of fine compound and continue grinding until surfaces are finished.
- Test each valve for a tight fit by making ten or twelve pencil marks across the valve seat and rotating the valve.
Tools required
- Valve spring compressor Amazon
- Drift 5/8 in with 3/8 in pilot Amazon
- Vibrating angle grinder reseating tool Amazon
- Grinding compound Amazon
- Valve grinder Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Exhaust valve seats finished on 45 degree angle
- Intake valve seats usually 45 degree, some 30 degree
Source: Hercules owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.