Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
Think I found the answer to my owne question on our sister US site - seems like its normal but I still can’t get my head around ithttp/forums.sohc4.net/index.php?topic=111546.0
Quote from: paulbaker1954 on September 20, 2019, 07:36:23 AMThink I found the answer to my owne question on our sister US site - seems like its normal but I still can’t get my head around ithttp/forums.sohc4.net/index.php?topic=111546.0Interesting conundrum as I've rebuilt my CB750 K1's petrol tap and about to test it, but cant open your link - could you repost please?
Funny posts in that link When the tank is not connected and tap is opened then fuel running out of one pipe will cause a vacuum in the other outlet if the intake side of the tap is not significantly greater than one outlet. Exactly the same principal of how the carb sucks fuel into the air stream only demonstrated in opposite fluids.In reality the whole system us sized to make sure the volume can always fill the float chambers under maximum demand so not supply shortage happensThe whole concept of a float chamber is to isolate it from tank and delivery pipes, all it has to do is have an excess supply that the float valves can regulate.My favourite is the missing lead theory stands to reason that fuel will go slower downhill without heavy lead added to it
So I am wondering if all my rough running issues are down to the 90 degreee nylon elbows I put between the petcock and carb fuel lines (see other post http://www.sohc.co.uk/index.php/topic,20087.30.html)What I am getting at is that by putting smaller bore connectors in the fuel lines I am getting fuel starvation in carbs 1 and 2 due to a flow imbalance
Certainly possible that altering flow will change this and dependant on size restrictions. Can't remember if you rigged some float height checks to your carbs? If you have them then you could run it with them fitted and observe fuel level. Generally petrol will get through most gaps as anything a bit iffy will give you a leak. But if you restrict it below engine usage then at some point it will impair float bowl level. It's usually seen when using higher rpm but letting it tickover would have the potential to let it recover.That "vacuum" affect I've noted above, could come into play if you've restricted ALL lines, as if 3/4 are asking for fuel (depleted carb level) they could in effect be switching off the 1/2 line by causing a more constant draw on the tap. You're going to have to suck-it-and-see to prove or dispell it.
I bought some of this Paul.It's almost the same as the OE piping but made from Nitrile.Not been able to test it yet as the bikes nowhere near ready to run yet, however I'm sure others on here have bought the same pipe and found it works just fine.https://www.ebay.co.uk/itm/Nitrile-Rubber-Smooth-Fuel-Tube-Petrol-Diesel-Oil-Line-Hose-Pipe-Tubing-NBR-1MTR/140693835989?ssPageName=STRK%3AMEBIDX%3AIT&var=440044001336&_trksid=p2057872.m2749.l2649