First Generation Ascots > Tech Section
Petcock fuel flow
johnnymot1:
I'm feeling a bit snake bit on this new acquisition. My engine noise remains a mystery, but I'm heading toward the piston pin.
The tank on this bike was horrific. A true home made coating job that peeled. My solution a nice clean, spare tank to get this machine to fun for more than 30 seconds to hopefully finallly diagnose my noise. My issue now..... Fuel doesn't flow from my petcock...Not with vacum applied, and not on reserve.
I took the petcock apart and it's as clean as can be, and the diaphragm is fine. I even put the mitghty vac on the fuel outlet and pumped and I hear "bubbling" in the tank, but no fuel. What am I missing here? :(
J6G1Z:
You can swap the petcock diaphragm spring to the other side of the diaphragm making your petcock full manual control. I have done this on my bikes, as I don't really care for the vacuum operation feature.
http://ascot500.com/index.php?topic=256.msg1070#msg1070
Don't know if this will resolve your issue, but it's something that you could try. Just don't forget to secure your petcock after shutting off the engine.
Good luck
J.
johnnymot1:
I'm going to be a little more methodical today, re-clean the in tank screen, the bowl screen and used some compressed air. Pretty simple operation, but apparently its suddenly "rocket science" for me! Both bikes I'm interchanging parts on have been sitting for a year (since I've owned them at least) and maybe more, so there may be some extra varnish cleaning in order for those parts.
Interestingly enough, when I pulled the petcock from the tank that had been improperly coated, someone had already made the spring switch to bypass the vacum diaphram. Given the overall condition of this bike, and it's knock that is looking/sounding more and more like a wristpin, I'm wondering if at some point they may have left the petcock on and fuel washed down the cylinder. The fuel bowl and screen at the bottom of the petcock was full of large flakes of the tank coating. :o
WTF304:
--- Quote from: J6G1Z on October 26, 2014, 08:48:59 am ---You can swap the petcock diaphragm spring to the other side of the diaphragm making your petcock full manual control. I have done this on my bikes, as I don't really care for the vacuum operation feature.
http://ascot500.com/index.php?topic=256.msg1070#msg1070
Don't know if this will resolve your issue, but it's something that you could try. Just don't forget to secure your petcock after shutting off the engine.
Good luck
J.
--- End quote ---
So switching the spring to the other side will get rid of the vac operating system, that's good to know should help alot cold starting and later on so it's not starving for fuel. One question .... fuel won't come dumping out of the vac port on the tank ?
J6G1Z:
There should not be a vacuum port on the tank. The vacuum source at the carb needs to either be plugged, or replace the vacuum line that runs from the petcock to the carb. I chose to eliminate that line & installed a new rubber vacuum port cover, or plug, on the carb.
J.
PS. YOU MUST ALWAYS REMEMBER TO MANUALLY CLOSE THE PETCOCK WHENEVER YOU KILL THE ENGINE.
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