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Vacuum petcock - abuse?

Started by GeoRocket, September 05, 2021, 04:41:57 PM

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GeoRocket

Hello All -
I have a 1995 FLHT, and I recall reading somewhere that the bike should not be started with the manual petcock valve in the "Off" position or the diaphragm could be damaged.
I have checked the FSM and owners manual and I can't find any warnings about this.
I am asking because I would like to shut the manual valve and run the fuel out of the float bowl at the end of the season.
Also - my bike has had the recall for the petcock diaphragm that was due to MTBE compatibility I believe.  Service Bul. M-1063A IIRC.
Is it true that I can damage the diaphragm by starting or running the engine with the manual petcock valve in the "Off" position?
Thanks for your advice.  This forum is the greatest!  Happy Memorial Day everyone.
George

thumper 823

Do yourself a favor and install a petcock without the
babysitting device, as it will surely let you down one day.
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Rising from the Ashes  UHIH

FSG

Quote from: thumper 823 on September 05, 2021, 04:44:38 PM
Do yourself a favor and install a petcock without the
babysitting device, as it will surely let you down one day.

:agree:   OR   convert what you have to Full Manual by disabling it's Vacuum Operation

yes it was M-1063/A/B Vacuum Operated Fuel Valves under Safety Recall Code 088

moving the coil spring to the other side of the diaphragm disables the Vacuum Operation,
and you MUST then rotate the Petcock to the OFF Position.

this has been mentioned many times on HTT over the years and only works on EVO, 1st and 2nd year TC's,
for sure won't work on a 2003 Softail as the Petcock itself changed






Flhfxd

Mine has been flawless since the bike was purchased in 1994. Bike has somewhere north of 100,000 miles on it. I run the carb dry every fall before I store the bike.
"And the road goes on forever...... But I got one more silver dollar.....'

Hossamania

Seems a poor design that would ruin the petcock by running it with it off. I doubt anything will happen by doing that, I did it many times when I had one. If that is the original petcock from '95, you have gotten your money's worth, and it may well fail just due to age. But a unit in good condition should not fail by running it in the off position. My brother's just failed this year on his '96, he put another vacuum operated unit on his as he doesn't remember to turn it off and on.
I prefer manual petcocks, but it is a safety issue that they get turned off every time the motor is shut down. If it is not something you will be vigilant about, stay with vacuum shut off.
If the government gives you everything you want,
it can take away everything you have.

GeoRocket

Hi Guys -

Thanks much for the responses.

Hoss - I also prefer manual petcock, and I always turn mine off.  Old and good habit from experience.  Good to know you haven't had any problems.

Thumper - No "babysitting" device required.  As long as it works I will keep it. 

FSG - Thanks for this good detail that you always provide!  I was aware of the "hack" you mentioned to disable the vac function.  I was more concerned with a diaphragm failure, which would cause fuel to leak past the failed diaphragm and out the atmospheric vent.  This was the basis of my question - how to not break it!

Flhfxd - Good to know your experience.  Thanks.

Hossamania

Eventually it will fail, that is the nature of diaphragms! Just a matter of when. And where.
If the government gives you everything you want,
it can take away everything you have.

HogMike

Quote from: Hossamania on September 06, 2021, 07:26:55 AM
Eventually it will fail, that is the nature of diaphragms! Just a matter of when. And where.


I'm waiting for mine to fail on my 95 FLH. After all these years, crap gas here, 15K miles it's still working!

I've got a new manual one on the shelf I bought years ago for a replacement. It'll probably go bad before I get to use it!

:potstir:
HOGMIKE
SoCal

Burnout

Quote from: GeoRocket on September 05, 2021, 04:41:57 PM
Hello All -
I have a 1995 FLHT, and I recall reading somewhere that the bike should not be started with the manual petcock valve in the "Off" position or the diaphragm could be damaged.
I have checked the FSM and owners manual and I can't find any warnings about this.
I am asking because I would like to shut the manual valve and run the fuel out of the float bowl at the end of the season.
Also - my bike has had the recall for the petcock diaphragm that was due to MTBE compatibility I believe.  Service Bul. M-1063A IIRC.
Is it true that I can damage the diaphragm by starting or running the engine with the manual petcock valve in the "Off" position?
Thanks for your advice.  This forum is the greatest!  Happy Memorial Day everyone.
George

Fear Uncertainty and Doubt

You cannot damage the petcock in any way operationally.

Where does crap like this come from?

Be careful tampering with the petcock can void your warranty!    :bike:
They don't call me Ironhead Rick just because I'm "hard headed"

motorhogman

"You cannot damage the petcock in any way operationally."

:agree:

Mine will turn 21 years old Sept 11th, 117,000 mi and I'll admit I have no idea how many times I have started this bike and had it run a bit and die.. OHH sheeet ! forgot the petcock again.
where's the points and condenser ?<br />Tom / aka motor

GeoRocket

Burnout asked: "Where does crap like this come from?"
Ref: 101 Harley-Davidson Performance Projects for Evolution Big Twins and Sportsters by Kip Woodring and Kenna Love ISBN 0-7603-0370-3.
Regarding the vac petcock, page 70 states: "The tremendous initial suction from the engine firing with the lever in the off position just rips up the diaphragm."
I bought this book recently (used) and it is full on inaccuracies and nearly worthless IMO.
I was sure I had read about this somewhere else but I don't recall where.
Thanks everyone - good to know this wont be any problem.
Happy Labor Day.
George

Burnout

Silly rumors like that should get stomped down right away.

They don't call me Ironhead Rick just because I'm "hard headed"

thumper 823

Quote from: motorhogman on September 06, 2021, 11:15:44 AM
"You cannot damage the petcock in any way operationally."

:agree:

Mine will turn 21 years old Sept 11th, 117,000 mi and I'll admit I have no idea how many times I have started this bike and had it run a bit and die.. OHH sheeet ! forgot the petcock again.

Hate to disagree with ya, But i know of several that have quit because of bad thingamajiggies. (petcocks)  Mine for one.
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Rising from the Ashes  UHIH

motorhogman

Quote from: thumper 823 on September 19, 2021, 04:32:13 AM
Quote from: motorhogman on September 06, 2021, 11:15:44 AM
"You cannot damage the petcock in any way operationally."

:agree:

Mine will turn 21 years old Sept 11th, 117,000 mi and I'll admit I have no idea how many times I have started this bike and had it run a bit and die.. OHH sheeet ! forgot the petcock again.

Hate to disagree with ya, But i know of several that have quit because of bad thingamajiggies. (petcocks)  Mine for one.

I remember hearing about the earlier ones failing when they first came out. . Doubt if it had anything to do with leaving them in the "off" position when starting the bike..
where's the points and condenser ?<br />Tom / aka motor

nmainehunter

I bought my 95 a couple of years ago and I tried to drain the gas through the petcock. Had no clue about the vac petcock and was concerned that there was no flow. Took me a bit to figure it out. I put a manual valve on.

thumper 823

I am more than sure they are one more safety item from a gobernent that wants to protect us from ourselves....
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Rising from the Ashes  UHIH