Petcock broken? and tylenol for my headache

[dolly_parton]

More banditry from this bike. 

After re-doing electrical connections and replacing plugs (one was completely black, the others looked rusted), I still cannot get this bike to start. It would put-put, but no life. I need to clean the carbs yet, but i want to at least drive it to my new place before the week is out.

So, methinks maybe a problem with the fuel. Water? I take the tank off to attempt a drain - I only have two settings on the petcock, ON and RES. I disconnect all lines, place on RES, and no fuel comes out. Not even a drip. Set to on...of course, nothing. So I go out, purchase a meter of vac line, and place on the vac nipple, set to ON, and start to suck. Nothing. I set it to RES, repeat, and a trickle of fuel comes out. It takes me five minutes of sucking and a headache to fill up a 1.75L bottle of everclear.

I thought RES was supposed to flow freely? Why is the ON position not allowing fuel to come through under neg pressure?? I can only hear a 'click', or light 'pop', and then it's like sucking cement up a straw. And why would this happen all a sudden...

[canyonbreeze]

RES is also vacuum controlled on the stock petcock.  What you need to set it to for free flow is prime.  The prime setting on the stock petcock is there but not marked.  If you turn from ON to past RES you hit a little screw, remove that screw and turn the rest of the way up for prime.

[dolly_parton]

That explains everything. But why was it impossible to draw fuel on the ON position? Does the clicking mean anything?

BTW, there were 2L of fuel left. Perfectly clear. Am I right to assume that the fuel filter is the little copper cone inside the clear plastic housing in the fuel line? It looks perfectly clean as well.

[canyonbreeze]

That's a fuel filter, not standard on the B400's.  Some people report fuel flow problems having a fuel filter inline and have to take it out.

Both ON and RES need the vacuum to flow.

[dolly_parton]

I *now* know I need neg pressure for both. But does that mean that the ON position is broken, if I am sucking the life out of myself and no drip? Why would this be? Broken after all?

[canyonbreeze]

Apparently broken.

[Red01]

Does sound like a petcock problem, but since you can at least get SOME fuel with vacuum applied in RES, the problem may not be the vacuum diaphragm (common failure point as these bikes age), but clogging around the pickup inside the tank may be your issue.  Not sure about the B4 & 250, but on the B6 & 12, there is a filter on the pickup, inside the tank.

[JmuRiz]

I may have a similar problem.  However I am having issues trying to take the fuel lines off the petcock...any tips/tricks to removing the fuel line from the petcock so I can take the tank off and check out all the parts?

Thanks,

[canyonbreeze]

If they're too stuck on maybe just cut them off and replace the hose.  That's what I had to do initially and the new hoses just slide on and off easily.

[dolly_parton]

cut any plastic fastener tie that may be on the line, and then twist the fuel hose back/forth...took me five minutes of awkward twisting to get the fuel line off.

[dolly_parton]

regarding the pickup clogging, would a can of compressed air do the trick? Should I soak any parts in some solution/chemical (i have heard pine-sol is good for this, can anyone confirm?)

[tomacGTi]

You do know there is the hidden Prime feature right?

Remove the screw on the face of the petcock and will allow you turn the knob further and fuel will flow without vacuum.

Search for it. It is well documented.

[pmackie]

Best way to clean the petcock is to remove it from the tank, take it all apart, and make sure everthing is clean an undamaged. This will allow you to completely drain the tank as well. As Red01 said, you can then inspect the top of the petcock to see if the screen (if there is one) is partially clogged.

As this point you want to make sure you've got fresh, water free, gasoline before you get carried away doing too much other work.

If is certainly possible that the reason that you don't have fuel flowing when the petcock is in the "on" position, is that there is not enough gasoline in the tank.

[dolly_parton]

Thanks, guys - the bike is now running...better than before.