TOPIC:

yep!
Ideally, you want .0V      That would be best.
.5V is a good tipping point for a voltage drop.
You can use this to test switches as well. Put a probe on each terminal when the switch is on(closed).
Just have to remember...the circuit must be on and all connections in the circuit connected.

I'm so frustrated. It's been a few days since last reply, shot and sweet to not confuse anyone. My started gave up one me and it was the weak starting issue once work (one of the issue because how worn out it was inside) second I parked the bike and put a blower on front to keep the bike from overheating, when started missing I remove the vacuum from petcock just in case and seconds later she idle fine, rev  like a beast not bogging out or nothing with such a harmony and no hesitation. I will switch to prime when started to lower Rpms doe to lack of gas and switch back to on(with the vacuum disconnect and capped) and stay running pretty good! Once I connect the vacuum after 10-15 sec she will idle rough and want to shut off again... I added a clear tube so I can see if gas was being sucked thru the vacuum line but it doesn't pull any gas so if she doesn't flood when on prime why with vacuum installed and "on" she has issues? Third thing she wasn't charging 12.5-9v was her range so basically nothing, tested rotor and seems fine bet rectifier didn't have me any reading so maybe at fault? I need to test it with more time at hands.  I'm so lost here I want to give up on her but in the other hands out of any vintage bikes out there I feel lucky to have her and want to fix her up.

It seems the vacuum to your petcock is turning off the fuel instead of allowing it to flow fuel.
The petcock may be dirty.

Do you have a clear fuel hose to check if fuel is flowing with vacuum connected?

Also, the vacuum hose may be obstructed or leaking, or the diaphragm may be torn, or somebody may have stretched the spring or replaced it with one that is too strong.

disconnect the vacuum line and cap it. Put petcock on prime. Start the engine. Should run good like you described

unplug vacuum line. If it runs crappy then it Sounds like Ike it might be the diaphragm in the Petcock. It’s not allowing fuel flow and causing a vacuum leak.

you can run the bike on prime without and problem. But you need to turn to on when parked, this will stop fuel flow. At that point your using it like a manual petcock

wrote:

It seems the vacuum to your petcock is turning off the fuel instead of allowing it to flow fuel.
The petcock may be dirty.
Do you have a clear fuel hose to check if fuel is flowing with vacuum connected?
    Yes I used a clear tube because I have read of petcocks leaking fuel thru the vacuum, That's not my case, tube stays dry at all times 

 

Mikaw post=846119disconnect the vacuum line and cap it. Put petcock on prime. Start the engine. Should run good like you described

unplug vacuum line. If it runs crappy then it Sounds like Ike it might be the diaphragm in the Petcock. It’s not allowing fuel flow and causing a vacuum leak.

you can run the bike on prime without and problem. But you need to turn to on when parked, this will stop fuel flow. At that point your using it like a manual petcock.
   Question, so I could try to remove my tank and use a vacuum pump (like to bleed brake lines)  hooked to the petcock. And see if when I apply vacuum to it gas do or don't flow? As well to confirm?

You can use a vacuum pump but the carburetor pulses it's vacuum--it's not a steady vacuum.
 

wrote:

wrote:

It seems the vacuum to your petcock is turning off the fuel instead of allowing it to flow fuel.
The petcock may be dirty.
Do you have a clear fuel hose to check if fuel is flowing with vacuum connected?
    Yes I used a clear tube because I have read of petcocks leaking fuel thru the vacuum, That's not my case, tube stays dry at all times 


 

I think he was asking you if you have tried a clear fuel, not vacuum, hose to see of the petcock will allow fuel to flow into the carbs when the engine is running and the vacuum hose is connected.

wrote:

no...the clear line is for the fuel line not the vacuum line on the petcock.

I totally missed that one. It makes total sense, yes I do have some from when I benched the carbs. That's a good idea I appreciate it. Hopefully I can get on it tomorrow to test it. 
 

wrote:

Mikaw post=846119disconnect the vacuum line and cap it. Put petcock on prime. Start the engine. Should run good like you described

unplug vacuum line. If it runs crappy then it Sounds like Ike it might be the diaphragm in the Petcock. It’s not allowing fuel flow and causing a vacuum leak.

you can run the bike on prime without and problem. But you need to turn to on when parked, this will stop fuel flow. At that point your using it like a manual petcock.
   Question, so I could try to remove my tank and use a vacuum pump (like to bleed brake lines)  hooked to the petcock. And see if when I apply vacuum to it gas do or don't flow? As well to confirm?

i see no reason why that would not work, but you will need to be sure that you apply the same amount of vacuum that the engine would normally supply, and I see no reason to remove the tank, just disconnect the fuel line, and drain it into a jar or other clean container.

TexasKZ post=846132

wrote:

Mikaw post=846119disconnect the vacuum line and cap it. Put petcock on prime. Start the engine. Should run good like you described

unplug vacuum line. If it runs crappy then it Sounds like Ike it might be the diaphragm in the Petcock. It’s not allowing fuel flow and causing a vacuum leak.

you can run the bike on prime without and problem. But you need to turn to on when parked, this will stop fuel flow. At that point your using it like a manual petcock.
   Question, so I could try to remove my tank and use a vacuum pump (like to bleed brake lines)  hooked to the petcock. And see if when I apply vacuum to it gas do or don't flow? As well to confirm?

i see no reason why that would not work, but you will need to be sure that you apply the same amount of vacuum that the engine would normally supply, and I see no reason to remove the tank, just disconnect the fuel line, and drain it into a jar or other clean container.
  Perfect, true. I don't know the exact amount maybe I can search it, to get it doe