fuel evaporating in carb?

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RangerRick

RangerRick

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Payson Arizona
This has been going on for some time, I have a Mighty Demon 750 Mechanical secondary, the fuel level visable through the sight glass drops over time, in a couple days it drops from the top notch to the middle, 2 more days and its at the bottom. Ive pulled the carb, replaced all gaskets, power valve and more. after much frustration I pulled it and put another carb on that i had laying around, that one does the same thing. Next thing I did was set up the 750 on stands on the workbench and fill the bowls with fuel, and monitored for leakage etc. It did the same thing, but no visable leaks,So Im wondering do todays gas evaporate that much, locally we have the winter blend with methanol? I think in it.
this may have been going on for quite a while and just never noticed it before. Any thoughts?
 
Yes you are experiencing the same as the rest of us "carb" users...today's fuel evaporates very quickly. Along with OEM type mechanical pump, I have added electric fuel pumps to help prime the carb so after the car sits awhile, excessive cranking is not required to fill the float bowls. Because of todays fuel, have had to change/tweek jetting to have a smoother running engine.
For electric priming pump the best for me so far has been Mallory, has internal bypass so no regulator is needed as stated on the tech sheet with the pump. Also the design allows easy pull thru so highways speeds are good with just the mechanical pump, or can use both pumps. I keep the electric as a back up on long highway cruises.
 
You've pretty much answered your own question. With the vast majority of cars on the road today being closed fuel injection systems, the evaporation problem of carbs is not a problem,,,, 'cept for us carb users.
 
femtnmax said:
Yes you are experiencing the same as the rest of us "carb" users...today's fuel evaporates very quickly. Along with OEM type mechanical pump, I have added electric fuel pumps to help prime the carb so after the car sits awhile, excessive cranking is not required to fill the float bowls. Because of todays fuel, have had to change/tweek jetting to have a smoother running engine.
For electric priming pump the best for me so far has been Mallory, has internal bypass so no regulator is needed as stated on the tech sheet with the pump. Also the design allows easy pull thru so highways speeds are good with just the mechanical pump, or can use both pumps. I keep the electric as a back up on long highway cruises.
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Good idea. My Dart is pretty hard to start after setting for a month at a time in the winter. At least it helps prime the oiling system before the engine fires. tmm
 
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