After months of cleaning and scrubbing, it was time for us to finally get down to business with the top-end rebuild on Ruby’s 1969 Honda CL 350 restoration. When we first checked out the bike, a compression test showed a serious loss of power on the 1st cylinder.
An ‘oil test’ led us to believe that the rings were the culprit, when oil dropped into the spark plug hole boosted compression to almost exactly what the good cylinder was reading.
So the rebuild began, and since the engine was completely torn down, a valve job was in order. The valves and springs were removed with a spring compressor, and all the parts put in individual zip-lock baggies for organization. MotoPreserve member Scott had the valve lapping lit, and we began grinding down the valves and seats with the course grit compound. Not surprisingly, the first valve went smoothly, leading us to believe we may be in for an easy job. Hmmmm, spoke too fast…
The second exhaust valve proved difficult to get seated. Working on it for about an hour, it became obvious that the valve must be bent – and that it was not going to seat itself correctly. Bad news!
Scott to the rescue again, when he gave us an extra exhaust valve from one of his 5 Honda CB 350 engines. The “new” valve was rough and rusted, but we threw it into the soda-blast cabinet, and cleaned it right up (above).
Very little lapping later, and we had a good, healthy seat. Seeing the tell-tale sign of the valve mating to the seat, with a clear ring of polished metal on both the valve and head, we moved on to the Intake valves, and were done in no time. All the valves were tested with non-drying Prussian Blue paste, and checked out OK.
Seems we have the head all buttoned up. The cylinders have both been honed, and we will now move on to the reassembly, with fresh gaskets and rings…