SuzukiSavage.com - Why has petcocke corrected itself?

DocNeedles

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Why has petcocke corrected itself?
08/04/09 at 15:20:41

Awhile ago I modified my fuel delivery because of unburnt gas through the exhaust and my plug carboning up. The suggestion from a mechanic friend and this website said to disconnect the vacuum line and run it on Prime, remembering to turn Pri off when stopping the bike since if I didn't fuel would continue to flow and would fill up the crankcase. I did this and it helped tremendously with only a bit of unburnt gas happening at times and the plug getting carboned less frequently. Today I ran the bike to the store and I forgot to put petcock on Pri and it didn't cut out!!! I rode back with it on the regular setting and again it didn't cut out.
The vacuum line is still plugged and I am tempted to connect it back up. Any suggestions to what is happening?
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youzguyz

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Re: Why has petcocke corrected itself?
Reply #1 - 08/04/09 at 15:31:58

It's obvious that the air that is trapped in the vacuum line was hot when the line was plugged. Now that it has cooled down, the volume of the air is trying to shrink, and is creating a vacuum in the line which is keeping the gas flowing.

AND I have land in Florida for sale .. and a 2 for 1 special if you buy my bridge in New York as well.

Actually, it sounds like your petcock is really broke bad, and the diaphram is distorted (keeping the gas flowing) or leaking. I would not hook that vacuum line backup or you could pull gas into the cylinder. You can test that by pulling off the plug and pulling a vacuum on the line manually. (syringe or your mouth.. carefully). If you pull gas from the petcock, very bad.

And why would leaving the gas running to the carb put gas in the cylinder and then the crankcase? It gets stopped by the float valve. And if that fails, it goes out the vent lines.. right?

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verslagen1

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Re: Why has petcocke corrected itself?
Reply #2 - 08/04/09 at 15:46:22

The question is... where is the extra gas coming from?

Ok, you've plug the vac line and that seems to have fixed the issue.
So more than likely, the petcock diaphram was leaking gas into the vac line and fed straight into the intake.

Other issue, why didn't the bike flood out the crankcase when you left the petcock on prime? because your float valve works correctly right now. The petcock auto on/off is supposed to be a backup for this.

And... you forgot to put petcock on Pri and it didn't quit on you. Number of possibilities, sunspots, total eclispe, diaphram sealed during low atmospheric pressure and high pressure ridge is pushing the petcock open allowing gas to flow. yada yada.

All in all, if you suspect the diaphram leaking gas into the vac line, DON'T HOOK IT BACK UP! If you have a small bottle that you can rig into the vac line so that any gas leaking thru will catch and confirm the leak would be my next action. if no leak then I'd concider another step, total disassembly of the petcock. I got a spare that I took apart, those nodules that form in carbs when gas is left to stand too long, formed in there. And there was corrosion. Could be what's holding the petcock diaphram operated valve open.

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Boule’tard Serious Thumper ModSquad Offline Master of the Obvious Posts: 1620 Austin TX Gender:	Re: Why has petcocke corrected itself? Reply #3 - 08/04/09 at 19:51:17 Man, I'm glad I ditched that POS for a manual petcock. One stock petcock available, only 2000 miles worth of gas run through it, available for the price of shipping to British Columbia.
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Digger

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Re: Why has petcocke corrected itself?
Reply #4 - 08/04/09 at 20:28:34

DocNeedles wrote on 08/04/09 at 15:20:41:

Awhile ago I modified my fuel delivery because of unburnt gas through the exhaust and my plug carboning up. The suggestion from a mechanic friend and this website said to disconnect the vacuum line and run it on Prime, remembering to turn Pri off when stopping the bike since if I didn't fuel would continue to flow and would fill up the crankcase. I did this and it helped tremendously with only a bit of unburnt gas happening at times and the plug getting carboned less frequently. Today I ran the bike to the store and I forgot to put petcock on Pri and it didn't cut out!!! I rode back with it on the regular setting and again it didn't cut out.
The vacuum line is still plugged and I am tempted to connect it back up. Any suggestions to what is happening?
DocNeedles

Doc,

What your story tells me is that you no longer can shut off fuel flow with your petcock.

I'd get a new OEM petcock, or get a Raptor petcock. I went the Raptor route last week and it is working great.

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Digger
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DocNeedles

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Re: Why has petcocke corrected itself?
Reply #5 - 08/04/09 at 21:27:19

verslagen1 wrote on 08/04/09 at 15:46:22:

The question is... where is the extra gas coming from?

Ok, you've plug the vac line and that seems to have fixed the issue.
So more than likely, the petcock diaphram was leaking gas into the vac line and fed straight into the intake.

Other issue, why didn't the bike flood out the crankcase when you left the petcock on prime? because your float valve works correctly right now. The petcock auto on/off is supposed to be a backup for this.

And... you forgot to put petcock on Pri and it didn't quit on you. Number of possibilities, sunspots, total eclispe, diaphram sealed during low atmospheric pressure and high pressure ridge is pushing the petcock open allowing gas to flow. yada yada.

All in all, if you suspect the diaphram leaking gas into the vac line, DON'T HOOK IT BACK UP! If you have a small bottle that you can rig into the vac line so that any gas leaking thru will catch and confirm the leak would be my next action. if no leak then I'd concider another step, total disassembly of the petcock. I got a spare that I took apart, those nodules that form in carbs when gas is left to stand too long, formed in there. And there was corrosion. Could be what's holding the petcock diaphragm operated valve open.

I unplugged the vacuum line and no gas came out. I then replaced the petcock with a new OEM one I bought a few years ago and when it started up I again experienced unburnt gas from the exhaust, with vacuum connected or unconnected. When I ran it later after it had cooled there was less unburnt gas. It seems to happen more so when the engine is hot. The only thing I can think off is to adjust the carb. Oh, I also checked the spark plug and it was fouled with black flakes, not oily residue.
DocNeedles

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serenity3743

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Re: Why has petcocke corrected itself?
Reply #6 - 08/05/09 at 08:49:46

Boule’tard wrote on 08/04/09 at 19:51:17:

Man, I'm glad I ditched that POS for a manual petcock. One stock petcock available, only 2000 miles worth of gas run through it, available for the price of shipping to British Columbia.

So you replaced the petcock even though nothing was wrong with it? I'll take you up on your offer, if you're serious. I assume it includes the vacuum line? PM me, okay?

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Charon Serious Thumper Offline Posts: 1811 Harvard, NE Gender:	Re: Why has petcocke corrected itself? Reply #7 - 08/05/09 at 18:38:40 There seem to be a lot of comments about the petcock and petcock failures on this forum. Is the S40/Savage unique in this problem? Vacuum petcocks have been around since at least as far back as my 1983 Suzuki Tempter, and I don't see many comments about failures in the motorcycle press. Am I missing something?
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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Why has petcocke corrected itself? Reply #8 - 08/05/09 at 19:11:28 I've never heard of failures before either ,I think Its because a lot of them don't have many miles on them for their age.
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Digger

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Re: Why has petcocke corrected itself?
Reply #9 - 08/05/09 at 19:44:48

Charon wrote on 08/05/09 at 18:38:40:

There seem to be a lot of comments about the petcock and petcock failures on this forum. Is the S40/Savage unique in this problem? Vacuum petcocks have been around since at least as far back as my 1983 Suzuki Tempter, and I don't see many comments about failures in the motorcycle press. Am I missing something?

The guys over on my KLR forum complain a lot about their petcocks.

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Digger
2001, Metallic Glacial Blue, Raptor Petcock, Verslavy (first hole) (otherwise, mechanically, the bike is stock), 13,xxx miles
I don't own a cage.
www.astronautbiker.com

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