SuzukiSavage.com - Fuel petcock

Gyrobob

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Re: Fuel petcock
Reply #60 - 09/25/11 at 17:13:03

Routy wrote on 09/25/11 at 15:59:32:

HJH wrote on 09/25/11 at 12:47:57:

Are you kids ever going to quit fighting?

HUH ?? Whats that about ??

HJH just forgot to insert the smiley to show us all he was teasing us. Right, HJH?

I hope the issue is settled now. (not that it matters very much)

To sum up, there is no energy used to keep the vacuum petcock open. There is only a force used, not energy (or work done).

IOW, the level of vacuum downstream of the carb is the same for a stock petcock and a Raptor petcock.

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gerald.hughes Serious Thumper ModSquad Offline FSO Posts: 1100 Tucson, Az Gender:	Re: Fuel petcock Reply #61 - 09/25/11 at 17:20:01 I am a little confused. Have the "Petcock" wars replaced the "Oil" wars? What is the petcock equivalent of Klotz?
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Gyrobob Serious Thumper Offline Posers ain't motorcyclists Posts: 2571 Newnan, GA Gender:	Re: Fuel petcock Reply #62 - 09/25/11 at 17:22:02 gerald.hughes wrote on 09/25/11 at 17:20:01: I am a little confused. Have the "Petcock" wars replaced the "Oil" wars? What is the petcock equivalent of Klotz? Raptor
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drums1 Serious Thumper Offline '87 Savage Bashed--Down for the count Posts: 664 Racine, Wisconsin Gender:	Re: Fuel petcock Reply #63 - 09/25/11 at 18:13:40 So, if Raptor is to petcock, as Klotz is to oil, then I assume, since you have Raptors on the twin RYCA bikes, you also use Klotz in them both also ??
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Gyrobob

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Re: Fuel petcock
Reply #64 - 09/25/11 at 19:13:32

drums1 wrote on 09/25/11 at 18:13:40:

So, if Raptor is to petcock, as Klotz is to oil, then I assume, since you have Raptors on the twin RYCA bikes, you also use Klotz in them both also ??

Roll Eyes

cute!

Your "logic" is entertaining, but I would submit that a Raptor is a change from original configuration while using Klotz is just another acceptable alternative -- no change in configuration.

Anyway, I was only being a smart aleck when I said "Raptor" in response to Gerald's question.

FWIW, and at the risk of reigniting another "war",... our bikes will be using Rotella Synth.

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Routy

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Re: Fuel petcock
Reply #65 - 09/25/11 at 19:36:13

Quote:
It is a tiny force applied for an instant to move the diaphragm. Once the diaphragm is moved, no more work is being done.
-----------------------------------------------------------------------
I was under the impression that the valve is "normally closed", which means it is held open against spring pressure. If this is true, then the quoted statement is incorrect.
That doesn't change anything, but thats beside the point,......ain't it ?

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Rich
'07 S40 Blvd stocker, except drilled OEM exhaust and white spacer mod...1/2 (.055)

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arteacher Serious Thumper Offline Ride as if your naked and invisable! Posts: 2581 London ontario Gender:	Re: Fuel petcock Reply #66 - 09/25/11 at 19:45:08 +1
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Gyrobob

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Re: Fuel petcock
Reply #67 - 09/26/11 at 05:46:10

Routy wrote on 09/25/11 at 19:36:13:

Quote:
It is a tiny force applied for an instant to move the diaphragm. Once the diaphragm is moved, no more work is being done.
-----------------------------------------------------------------------
I was under the impression that the valve is "normally closed", which means it is held open against spring pressure. If this is true, then the quoted statement is incorrect.
That doesn't change anything, but thats beside the point,......ain't it ?

Yes, the valve is normally closed when the engine is not running. The spring holds the valve in the closed position.

Start the engine and vacuum is applied to the diaphragm in the petcock. The vacuum lowers the pressure on one side of the diaphragm, sucking it to move against the spring pressure, opening the valve, letting fuel get to the carb.

In any event, there is no work being done by the vacuum once the diaphragm is moved and the fuel starts to flow. The tiny bit of work being done happens in the blink of an eye, and is completely finished once the valve has been opened. The vacuum situation downstream of the carb, then, is exactly the same for both types of petcocks, Raptor or stock. There is no energy being used to hold the fuel valve in the petcock open.

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arteacher Serious Thumper Offline Ride as if your naked and invisable! Posts: 2581 London ontario Gender:	Re: Fuel petcock Reply #68 - 09/26/11 at 11:08:38 OK what does hold it open and what is it called? force? work? energy? magic? If it is a force, what kind is it? Where does it go when you don't need it anymore?
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HJH

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Re: Fuel petcock
Reply #69 - 09/26/11 at 11:22:03

And after all of this, have any opinions about the correctness of the petcock fix(or not) changed? Reminds me of discussions of trucks, cars, women, guns, politics, religions, and brands of beer. Lots of verbiage from the competing(discussing) parties, and the rest of us just do it or not, based on the information supplied, without engaging in the discussion.

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Silver '02, Dyna, Raptor Petcock, VM carb at 6000 ft, Q2 needle, 12.5 pilot, 170 main, UFO, Verslavy, Pirelli 150/90, Plexistar 2 Windshield, K&N filter, Tourmaster II bag, Progressive Shocks

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arteacher

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Re: Fuel petcock
Reply #70 - 09/26/11 at 11:30:29

This all started when I asked why my idle went up after I changed petcocks.
I still haven't gotten an answer. :'( :'(

You were busy at the time and just didn't notice it ....

Seriously, you capped off a potential vac suction leak draw point ....

.... and you made sure your bowl was always full right up to the top fill point at all times.

Either (or both acting together) may have richened your idle mixture slightly enough to make your idle speed go up a little bit.

Plus the fact you are running the snot out of your bike now since it is running better for you, so you are getting your engine loosened up a bit more than you used to (and your idle speed goes up a bit for that reason too).

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« Last Edit: 09/26/11 at 14:02:55 by Oldfeller--FSO »

white '07, Raask exh, Corbin seat, slipstreamer shie, Raptor, Routy's fwd controls, Baron tach, Frisco bars, Isogrips, Headlight and taillight modulators, Dial-a- jet, AME 9 deg chop kit, K&N air flt

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Gyrobob

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Re: Fuel petcock
Reply #71 - 09/26/11 at 13:28:50

arteacher wrote on 09/26/11 at 11:08:38:

OK what does hold it open and what is it called? force? work? energy? magic? If it is a force, what kind is it? Where does it go when you don't need it anymore? Huh

This all started when I asked why my idle went up after I changed petcocks.
I still haven't gotten an answer. :'( :'(

A force holds it open.
--- The force is supplied by the intake vacuum working on one side of the diaphragm. This force is enough to overcome the spring force trying to hold the petcock valve closed.
--- When the engine is shut off, the vacuum goes away, which removes the hold-the-valve-open force from the diaphragm. The force from the spring then pushes the diaphragm back, closing the valve, shutting off the fuel.

There's probably more than one reason why your idle rpm increased when you changed petcocks. My main suspicion would be that you had a leak somewhere in the vacuum line going from the carb to the petcock, or in the petcock diaphragm itself. When you replaced the petcock, you coincidentally fixed the leak, causing the increase in rpm. This should also have resulted in a smoother idle.

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Gyrobob

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Re: Fuel petcock
Reply #72 - 09/26/11 at 13:47:47

HJH wrote on 09/26/11 at 11:22:03:

And after all of this, have any opinions about the correctness of the petcock fix(or not) changed? Reminds me of discussions of trucks, cars, women, guns, politics, religions, and brands of beer. Lots of verbiage from the competing(discussing) parties, and the rest of us just do it or not, based on the information supplied, without engaging in the discussion.

You are correct, methinks.

This discussion is one those just like those categories you mentioned. Guys who like revolvers will never like semi-autos. Liberals and conservatives will never see eye to eye. Loud pipe guys think loud pipes are great, quiet pipe guys think quiet pipes are great. Raptor petcock guys vs stock petcock guys,,.... so on and so forth.

Some folks feel the stock Suzuki parts work just fine when in good repair, and have the advantages of convenience (not messing with the petcock after every ride) and safety (the fuel shuts off when the engine shuts off).

Some folks feel the Raptor petcock is more reliable, more positive, easier to work with because it is smaller, and is more safe because it is less likely to fail in traffic. It's cheaper too.

Take your pick.

One other thing to keep in mind,.. we are not talking megabucks or major modifications here. If you change from one petcock to the other, and after a while you don't like it, change it BACK! Change it every month, FCS. It's not like you are converting to a RYCA CS-1 or something,...

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