Re: Fuel pump diaphragm
The diaphram will deform a bit normaly.It could have something to do with deminished volume,however,I would be more concerned with it's texture.Is it still soft and pliable,with no cracks? The cracks could be tiny, and only visable if you bend the rubber over. But I don't think that it's having a bit of 'sag' to it, is the only problem.<br /><br />The check valves will control the volume of fuel drawn into ,and forced-out of it. They don't normally fail, but can get minute particles of trash under them,causing them to hang open. They will also stick shut on an engine that has been allowed to sit for a year or more.<br /><br />But all that asside, if the diaphram is deformed, it's pretty tired, ane should be changed-out.<br /> You may have something in a carb's jet,or anything else typical of fuel starvation.<br /><br />Check the compression, as most pumps operate off engine compression.<br /><br />Clean the carbs up real good.<br />With an internally clean carb, try 'riching-out'<br />each one 1/8 turn out, and seeing if top end improves or gets worse. Too rich a mixture could foul plugs---Too lean can destroy the engine..Best to error on the side of rich.<br /><br />Examine plugs for color or lack thereof. Plugs can tell us a lot.
