Robert Dell Aquila

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Hi yall, haven't posted on here in a minute. Hope all is well. Been trying to get the bike running smooth, however I seem to still have an air leak. With the bike running I sprayed around manifolds, head gaskets choke housing and throttle shaft seals and nothing happened. I can hear the air leak clear as day when I rev the engine. I put my ear next to the spot where the leak was the loudest and it was by my air filter/ inline fuel filter area. I sprayed carb cleaner at the inline filter and the bike bogged down. So my question is can I have a vacuum leak around the fuel line coming from my petcock to the carbs??? I added a 2nd petcock to the right side of my tank but keep it in the off position because it was too much fuel. I believe my right side is getting to much fuel, when I pull my right plug it seems wet. Perhaps it is my fuel filter and fuel line configuration that is causing these problems. Any help is much appreciated!

P.S - I am running 90* rock filters with brand new fuel line.

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... I can hear the air leak clear as day when I rev the engine. I put my ear next to the spot where the leak was the loudest and it was by my air filter/ inline fuel filter area...

That's an odd area.
Try jamming a hose in your ear, probe around with the other end, and see if you can pinpoint it...
 
That's an odd area.
Try jamming a hose in your ear, probe around with the other end, and see if you can pinpoint it...

thats something I've not heard in a long time 2M .....I used to sync the SU carbs on my MGBs with a length of hose stuck in my ear :)
I guess if the tank vent was blocked, that might cause excessive vacuum on the fuel line connections
 
I added a 2nd petcock to the right side of my tank but keep it in the off position because it was too much fuel.
This seems to be pointing at your real problem.
Have you done the float dip test? Your float valves need to be working (reliably stop fuel flow) for the engine to run properly.
PS mikalar fuel line clamps
 
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That's an odd area.
Try jamming a hose in your ear, probe around with the other end, and see if you can pinpoint it...

Yea I never heard or read about a leak in that area either. But when I listen to where the air is getting sucked in it's definitely not around the manifold/head gasket area where it typically is. Its seems to be the loudest around the air filter area and only place that boggs down when I spray the fuel line.
 
This seems to be pointing at your real problem.
Have you done the float dip test? Your float valves need to be working (reliably stop fuel flow) for the engine to run properly.
PS mikalar fuel line clamps

Yes, floats are solid and the height is set. Float valve is not sticking. I took 5twins advice and added the 2nd petcock because I have a split tank and wouldn't be using all the fuel in the tank.
 
am i missing something here ? :umm:
if you have vacuum type petcocks then the they are operated by the vacuum of the engine when it is running. If you have loose fuel line connections , (or your fuel tank vent is blocked, ) then the engine vacuum will draw air from wherever it can,.... like your fuel line connections .
 
am i missing something here ? :umm:
if you have vacuum type petcocks then the they are operated by the vacuum of the engine when it is running. If you have loose fuel line connections , (or your fuel tank vent is blocked, ) then the engine vacuum will draw air from wherever it can,.... like your fuel line connections .
I believe I have manual petcocks. Not the vacuum type ones. Which is why its strange that the idle dips when I spray the fuel line and filters.
 
I think if a fuel line was leaking air it would leak fuel as well. Personally, I don't add any extra filters in the lines. It's really cramped in that area and I've read about too many issues with them (leaks, blocking flow). I've never had any dirty or plugged carb issues since I've owned this bike. In fact, I never had any issues with any bike I ever owned. None ever had extra fuel filters installed.
 
You are suspecting the fuel lines.
Simply remove that fuel line set up including the inline filters. Your 1/4” automotive fuel lines with hose clamps screwed tight isn’t ideal anyway.
You need 6mm higher quality and more flexible fuel line in the end.
I’d suggest temporarily replacing the lines with transparent , one piece lines so you can watch the fuel flow while diagnosing for now.
-R
 
It vents excess crankcase pressure so yes, you probably would hear some air hissing with no hose on there. The original hose ran back down behind the engine or into the left side cover above the chain on early models. Later models connected it to the airbox to recycle any oil vapor back through the engine. With pods, most of us attach either a little filter or a power brake check valve to the end of the hose. I position mine over my pod. The pods are oiled anyway, so if any comes out the breather, it will just go through my pod back through the engine. I've never noticed any oil coming out though.

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It vents excess crankcase pressure so yes, you probably would hear some air hissing with no hose on there. The original hose ran back down behind the engine or into the left side cover above the chain on early models. Later models connected it to the airbox to recycle any oil vapor back through the engine. With pods, most of us attach either a little filter or a power brake check valve to the end of the hose. I position mine over my pod. The pods are oiled anyway, so if any comes out the breather, it will just go through my pod back through the engine. I've never noticed any oil coming out though.

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Wow, you guys are epic. Alright I will install the breather tube today. Would I just put regular fuel line on it and route it over the air filter?
 
If yours is the same diameter as the earlier dual outlet style ? Any garden supply store or hardware store sells under ground sprinkler black plastic tubing sections for very cheap. It is a nice fit. A hair dryer can help you fit and shape it. I just ran it right straight into the battery box hole area
:D
 
It takes larger diameter hose, near 1/2" I think. You might be able to find some at an auto parts store. I bought the stuff from Mike's because it was an exact replica of the original (thin wall).
 
Hell yeah thanks guys. I never ran this on my bike before, originally I thought the "wet" gas on my plugs were oil and assumed it was a bad valve seal. Do you think not having this PBC vent could have caused the seals to wear down? Was going to do a top end rebuild but thought I'd post here first about my problem.
 
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