bike mathews 750
A 1981 CB750C getting some attention. Low on power, and especially since the customer lives at high altitide. We descided to remove the engine and look at the top end. Engine on the engine stand.
Cylinder head. Inspecting everything. Valves show the usual recession resulting in lower than normal cylinder compression. Cylinder head off, vacuuming out the cylinders of carbon before removing the cylinders so junk doesn't fall into the crankcase.
Cylinders show wear and unevenness. Some carbon on the piston crowns. Not excessive. More. This is the head gasket.
A lot but not unusual for having the miles it does. A little bluing on the piston pins. The whole top end is being inspected, measurements taken.
Engine is being carefully handled. It was decided to go ahead and go into the bottom end of the engine. This is a good opportunity to replace the cam chain, which is a high-wear item on these engines. Once that was done, the bottom end was zipped back up. Note the paint has been touched up also.
The cylinders were bored for special oversize pistons. Afterward, the cylinders are honed. The piston rings are carefully fitted and gapped to the new bores.
The chamfers are smoothed off to make reassembly of the engine easier. The cylinder's gasket surfaces are prepped. All good.
Using special factory ring compressors the cylinders are reinstalled. Head work begins. Found that the B cam chain tensioner mount needed thread repair.
The head's valve seats received very careful meticulous refinishing. Special diamond-faced stones used. Head fully cleaned up and gasket surfaces prepped.
Stainless steel valves going in. Engine assembled with all newly-replated fasteners. Head installed and final assembly begun.
Intake cam sprocket receives slotting on milling machine using a rotary table. Close up. Increments of rotary table showing how the arcs are produced.
Finished sprocket. Cams are degreed. Sprocket on intake cam.
Carburetors had been rebuilt previously so this time it was just a flush-through that was needed. The usual issue with the spanking marks was evident, so this was taken care of. Closeup.
Special tool used. Also while in there renewed the clutch dampers. Clutch completed.
Found the usual electrical issues. Fixed them. Loose spark plug wires also.
Result of engine build. After a 40-mile shakedown the bike was sent home.