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.

[WTF304]

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.

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.

[WTF304]

On the petcock, there are 3 ports. Fuel feed, a vacc source back to the carb, and i could be wrong but there is one used factory as just a breather or vent hose. Kinda figured the one on the carb would have to be blocked off, just curious if the fuel would leak out of the vent line or the vac feed from the carb to the diaphragm.

Only one way to know, I'd prefer to be able to manually control the fuel feed and many of my machines did.

[J6G1Z]

The petcock will not leak out of the two other ports unless the diaphragm is bad. If I recall correctly, one port is the vacuum side & the other is a vent to atmosphere to allow the diaphragm to move back & forth.

J.

[WTF304]

Cool thanks for the info, did it shorten up starting times for you? The electric start mechanism is not something i like to be cranking the piss out of. Parts to the system aren't as easy to find as they are to replace

[J6G1Z]

I follow a starting routine. Usually when I'm riding home, I close the petcock a few blocks from home & run the carb dry before parking my bike. I store my bike on the center-stand.

So... When it comes time to start, I check the crankcase oil level first, then open the petcock & push the bike outside. Usually this is enough time for the carb bowl to fill. I then crank the throttle WFO about 4-5 times to operate the accelerator pump to prime the carb. This squirts a bunch of raw fuel into the carb. Now pull the choke to full & then hit the starter. The bike should fire right up as long as your battery is strong. The FT Ascot really needs a strong & well charged battery to prevent excessive cranking of the starter.

Good luck
J.

[WTF304]

Routine is important, the way the linkage that work's the pump hardly even moves it though. I take the bowl off and manually work the accelerator pump gently to see how far it actually moves. I get a measurement by eye and then i bend the end of the linkage a bit so i get one good push from it. When the pump finally ends it's stroke the throttle valve is almost half open so i have about 1/2 to WOT that isn't working off the pump. Worked very well on my ice raced FT

[WTF304]

Well ... I'm a happy camper, i did take the fuel petcock apart and i swap the spring to the other side. Along with fresh gas, new fuel lines, carb cleaned and re-jetted with a 55 pilot and a 160 main .... plus a little twist of the accelerator pump linkage. She revs up quick and i don't even have to pump the throttle before starting, she fires up alot faster almost instantly. Air box is off though, got a new filter coming plus I'm going to clean it before it goes back in it's home. After that it's just a few tweaks away on fine tuning the air/fuel screw once more.

J6 ... just a simple thank you for posting up switching the spring.

[J6G1Z]

No problem. I can't take credit for the petcock modification though. I read about it on the Yahoo FT Ascot Owners Group. It also works on VT Ascots.

J.