Coughing during the start

[marts99ss]

This is my first post in this forum, I hope I can explained this problem clearly. I have a 89 PROV150. The engine is popping coughing during the starting process and stalls and only when it's cold but when it starts and gets going, I can turn off and on with no issues. When it starts it runs fine at all the speeds at idols fine also. One more condition that I have noticed is that the primer bulb does not get rock hard, 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 the fuel pumps? Any help would be appreciated.

This problem started right after I had rebuild the carburetors. I had some issues with the engine not idling correctly and coughing and stalling at idle. The lower two carburetors pilot jets were completely clogged.
Thanks for your help.

[Sequoiha]

sounds to me you have a link and sync issue, which includes air fuel mixture adjustments, coughing usually is an indication of a lean condition,, about the primer bulb, it will only be tight when you pump it, when the engine is running it is nothing but a fuel line and will be soft.. when you pump the primer bulb make sure the arrow on the bulb is pointing up,, hope this helps.

[marts99ss]

Thank you Sequoiha for your reply,
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. It does not cough or backfire when the engine is running. 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. Regarding sink and the adjustments of the pilot screws, I have fallowed the Yamaha manual. It says 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. Do you still think it could be a sync problem? It can't be a weak fuel pump? I know that what the primer bulb is used for and when to use it. The direction is in the correct way. What makes the primer bulb to hold the fuel and get hard?

[fuzzymaster]

Pumping bulb fills carb bowl, when full the needle valve seats, pressure builds in bulb because of check valve will not allow fuel to flow back from carbs.

[marts99ss]

How firm should the bulb get? I know before the start. Should it be firm so it can't be pumped anymore?

[fuzzymaster]

I believe if you squeeze it several times you will feel it get hard, firm, and that should be enough.

[madharchod]

when you press the primer bulb more fuel is being pushed in the engine and carbs, once the fuel filter bottle is full the carb will only take enough till the float in the carb seals the needle valve and then your primer bulb will become hard as ,and if this dosent happen then you have problem with your float,and as for coughing and spurting its the adjustment not done properly once it start it will run but then you will be wasting more fuel as the carbs will be not functioning the way they meant to be
cheers

[marts99ss]

So I should check the bulb, and if the bulb is ok then check the float. If bulb is ok but the fuel can be contently be pumped in to the carbs then it's the needle vales on the floats?

Is that how I would check the needle valves on the floats or is there any other way?

[liliepad1]

ID say try adjust mixture screws a little richer . On cold start up u need a little more fuel to keep it running.