This only happens when the engine is cold, like for the first start of the morning or after it has been off for two hours, and only when the starter is cranking the engine. The engine is popping, coughing, backfiring during the starting process and stalls and doesn't want to start. When it starts it runs fine at all the speeds at idols fine also. I can then turn it off and on with no problem. This problem came up right after I had rebuilt the carburetors because the engine was coughing and stalled during idle. Now it's not coughing at idle. I rebuilt carburetors two times because of this idle coughing. The first rebuilt didn't fix the idle cough because I didn't see the pilot jets to clean them. The Yamaha manual failed to point it out during the carburetor overhaul steps. But at this point after the first rebuilt I didn't have the starter backfire or cough problem. The second time I found the pilot jets and cleaned them out and the idle cough was fixed, but now I have this starter cough problem. I have fallowed the Yamaha manual. It says for the 1989 the turns out of the pilot screw for the ProV150 for the Port 1-1/2 +-1/4 and Starboard 1 +-1/4. I'm with in this perimeters.
One more condition that I have noticed is that the primer bulb does not get rock hard before I crank the engine. I have changed the primer bulb because of that reason but it still does not get completely hard. I don't know if they are related. Could it be a weak fuel pumps? What makes the primer bulb to hold the fuel and get hard? The bulb gets somewhat hard but it stays spongy.
One more condition that I have noticed is that the primer bulb does not get rock hard before I crank the engine. I have changed the primer bulb because of that reason but it still does not get completely hard. I don't know if they are related. Could it be a weak fuel pumps? What makes the primer bulb to hold the fuel and get hard? The bulb gets somewhat hard but it stays spongy.
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