40021 Ben Morgan Road Leonardtown, Maryland 20650 Copyright retained
Setting the cam gear on the YT-1 marine engine can be a most difficult problem when tackled for the first time. The gear being spiral means one has to take into account the initial mesh versus the final mesh rotation of the cam. Hopefully the following approach should avoid too many frustrating attempts to correctly time the valves.
1. The rotation of the YT-1 is counter clockwise facing the flywheel. Too many people have tried to start the YT-1 or other old time marine engines by cranking them clockwise. The common experience is the engine keeps backfiring and wants to run the other way, NUFF SAID!!!
2. The water pump eccentric if lightly pressed on the shaft makes a convenient hand-hold to rotate the cam.
3. Note the key ways on the shaft all line up.
4. Slide the water pump end bushing onto the shaft and then insert the keys in the shaft for holding the cam gear.
5. Note the cam gear key ways are lined up so that the peak of the exhaust valve cam is lined up with its keyway. The intake cam peak clearly does not line up with its keyway. The exhaust cam should be installed toward the water pump eccentric.
For our marine friends the water pump and the exhaust valve are on. the Starboard side of the engine. The intake valve is on the Port side of the engine.
6. If one holds the cam gear in their hand with the keyways facing away and the exhaust cam end toward the right, one should note the intake cam on the left end is in the same relative position as the exhaust cam peak except it faces toward the rear. Rotating the cam gear clockwise (relative to the exhaust cam) should indicate the closing of the exhaust valve immediately followed by the opening of the intake valve.
7. There is often a large overlap in the opening of the typical exhaust valve and the closing of the intake valve. On the other hand most old time, low speed engines with mechanically operated valves are very predictable on the closing of the exhaust valve followed within a few degrees with the opening of the intake valve. For this reason one should work with the closing of the exhaust valve followed by the opening of the intake valve.
8. One can visualize the YT-1 cam gear when it is correctly positioned in the engine with the keyway of the water pump eccentric facing forward, the exhaust valve will have just closed and the intake beginning to open.
9. When the flywheel rotates counter clock wise the cam shaft rotates clockwise when viewed from the water pump end of the shaft. The trick is to insert the cam gear with the exhaust cam towards the water pump so when the flywheel is pulled up on TOP DEAD CENTER the water pump eccentric keyway faces forward. There can be no question if one has the gears meshed correctly. Check the position of the piston through the spark plug hole. As the piston comes up on TDC the exhaust valve closes and the intake begins to open. Being off by one tooth in either direction will immediately be obvious. The really frustrating part of the operation is judging how much lead in meshing the spiral gear. Once you know how to determine the exhaust cam end and the final position of the cam shaft key-ways at TDC, persistence will overcome one's doubts!!
10. Once the valves are timed correctly it is a simple matter to time the ignition. Bring the piston up on TDC of the FIRING stroke. The Cuno timer drive shaft has a flat milled on it. The flat on the drive shaft should face aft when the piston is on TDC of the firing stroke. There is a -20 thd set screw that is in line with the flat on the drive shaft. By observing the relative position of the set screw one can determine the position of the internal wiper of the timer without removing the timer cover. With the flat facing aft the timer should be at mid range for advance/retard. Moving the timer handle towards the flywheel retards the spark.
11. To start the YT-1 put a few drops of gasoline in the priming cup. Set the timer handle straight up. Pull the flywheel up SMARTLY and the engine should normally start on the first pull. Once the engine starts, advance the spark and set the throttle. The typical YT-1 idles at about 150-180 rpm. The drip oilier should be set for about six drops a minute as it is the prime means of lubricating the forward portion of the crankshaft.