Fuel Pump woes

[bondibox]

A few years back my 1999 M750 konked out on me.  Turns out the fuel pump needed to be rebuilt - the diaphragms had ruptured, etc.  But I'm still having problems with it: Fuel is getting behind the diaphragm on the vacuum side, and that makes the pump stop working.  I'm confounded as to how the fuel is getting back there since it's a new rebuild and the diaphragm isn't perforated (and the screws are manly-tight).  One possibility I'm thinking of is that the vacuum line goes to the intake runners ... is it possible that fuel vapor is getting in the vacuum line, condensing, and then dripping into the pump chamber?

I want to fix this once and for all...  last night I dropped the bike on the right side and that was enough to foul the pump.  I'd replace the unit outright if it weren't for the possibility that fuel is coming through the vacuum hose.  Then again, if fuel is traveling down that hose, it would be a very common, systemic problem.

Has anyone else battled the Mikuni DF62 fuel pump and won?

[Howie]

Most likely the diaphragm is porous or a part is warped.  Unless there is something seriously wrong with your engine there is no positive pressure in that vacuum line.

[DJ]

Did you buy the Winderosa or Mikuni rebuild kit? I ran into the same issue when using the Winderosa, as it's utter crap and the membranes fall apart within a few months.

The Mikuni kit on the other hand is of much higher quality. I've not had a single problem with it since rebuilding: http://www.fokust.com/gallery/fuel_pump

Good Luck!

-dj

[bondibox]

I decided to get a new Mikuni dual outlet pump, and plug the extra outlet.

Does anyone have a crafty idea for plugging the outlet?  I went to the hardware store and bought a screw top hose barb and a pipecap, but the cap leaks.  I'd just as soon glue the cap on, but I'm not sure what to use -- i.e. will gas eat through locktite?

It's an ugly solution even if it works, so I'd like to find something better looking.

[Hedgehog]

Have you thought of using a "Y" connector to join the two lines?  That might make it look better.

[DJ]

It's an ugly solution even if it works, so I'd like to find something better looking.

Honestly I've never really liked how the fuel filter and pump look hanging out there on the frame. One of these days when I finally get some time to do a full tear-down I swear I'm going to find a better way to hide those things....