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Thanks for all the help getting my 750 back on its tires , almost as good as before it got vandalized when they tried to steal it .

ran into a problem recently though . a kawasucky tech said this little thing ( image included) was a fuel pressure regulator and if it wasn't hooked up to engine that gas would leak into case and mix with oil . cant find any info on it in Hanes or the service tech manual . anyone know for sure and if he is right where does the hose go ?

will submit pic's as soon as its reassembled again
 

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Yes it is a fuel pressure regulator , it needs to be on the return side of the fuel injectors so the fuel pressure at the injectors is held stable. If you put it before the injectors the pressure will drop after the regulators and you will not have a steady flow of fuel. The small fitting is just a vent.
 

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the small fitting isn't actually a vent, it's a port to the non pressure side of the diaphragm and is used in some applications to supply manifold vacuum to the non pressure side, which thereby reduces the fuel pressure by the amount of manifold vacuum. the theory is that this keeps the pressure drop across the injectors consistant and therefore the relationship between pulse width and fuel delivery. this was possibly important with analogue injection, but i really haven't found any reason to use it with the digital systems. ducati used it on the 851 and 907, but with the 888 they stopped using it. i often see people put hoses on the nipple, or like you get stressed when they see it or get told that something is not right or missing.

i did try hooking a manifold vacuum hose up to an m800 reg once to see if we could lean the part throttle out after using the trimmer to richen it up a bit, back in the days before we could flash the ecu. it seemed to make very little difference. if you drop it half a bar you should get about 8% leaner, but it didn't seem to really work that way.
 

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Thanks for the historic info, Brad. I've never seen the "vent" port of the regulator connected to a hose, so the next time I see an 851 at a show, I'll have to check it out.
 
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