Hi. I’m using a BAP fuel tap on my 1960 Dommie 99 project because I can’t find any other reliable main+reserve tap. The tap body is connected to a threaded collar screwed into the tank so that the operating lever can be reached and doesn’t foul the top frame rail. That threaded collar places the tap body below the level of the top frame rail, which makes the outlet of the tap sit very close to the Monobloc carb’s inlet banjo. In fact the distance is under 4 inches. I had hoped to fit an external fuel filter so that I could keep an eye on any rubbish that comes out of the tank. The only way I could fit a filter is to have a longer fuel pipe but to do that the pipe would have to go down below the level of the float chamber and then curve back up to the fuel inlet banjo. My questions are:
1. Does it matter if the fuel goes downwards from the tap but then has to go uphill for about 5 inches before it gets into the carb? 2. Is there a risk that when the fuel level gets a bit low in the tank, there won’t be enough pressure to push the fuel uphill to the carb?
3. Is there a risk of getting an air lock in the fuel pipe if I do this?
Thanks very much
Regards
Tony
Yes and yes
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beware fuel filter
Just to let you know a friend has just put a bike back on the road and fitted a common small plastic fuel filter in the line for the same reason as yourself, he did 30 miles before suffering coughing and banging and misfire, in fact the bike would not limp home, the new fuel had disintegrated the fine white mesh and blocked his carb. perhaps put your filter in a jar of the new petrol for a week to confirm its stability.
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A loop down won't trap air…
A loop down won't trap air. An upwards loop will.
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Far better you keep the filter horizontal and the fuel lines up as high as you can so there is a gravitational path to your float chamber. The only down side is when your out of fuel, you are out.
cheers
Jon