914 Runs Rough with Both Fuel Pumps On

Just a suggestion but we always actually test the float valves at every 200 hour inspection and at overhaul. This is done with a very accurate pressure gauge and the carburetor turned upside down with soap and water placed in the valve cavity. The H frame is resting on the valve at this point. Any foaming is a no-no the soapy water should hold with no bubbles up to six PSI. Somewhere between 6.25 and 6.4 the valve will blow and you will get water in your face. This really is the only positive way of testing that valve and valve seat.

Hi ,

On 914 , the carb gasket float chamber is VERY important !!!!! ( following air pressure from airbox )

Fit the last rubber step P/N : 830721

BR

Christian

I replaced the floats and needle valves and that solved my carb flooding issue.  But I did develop a new issue.  The engine stumbles now when I get into full boost.  If I advance the throttle very very very slowly with the vernier then it seems to run great.  But a normal smooth throttle advance causes the engine to either hesitate momentarily then go full boost or causes the engine to backfire and almost quit.  As soon as I pull it back to the 100% range or lower, it runs smooth.  I’ve removed, inspected and reinstalled float bowls thinking maybe it was sucking in some air.  No change.  Fuel return line is clear.  Differential Fuel pressure is reading about 4.1 psi.  I am suspicious of the 2/4 carb because the egt on that side is running hotter even with the needle now in the #4 position.  But pulling the bowl, checking the gasket, and reinstalling yielded no change.

I’m also wondering if my fuel filter may need to be replaced.  but I would think fuel pressure would be lower if there was a fuel supply issue.

anyway, the flooding issue is 100% better, but somehow I created this new issue.