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General Category >> Rubber Side Down! >> petcock-diaphram-vacum line-mod-etc ?
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Message started by Routy on 08/24/09 at 07:50:56

Title: petcock-diaphram-vacum line-mod-etc ?
Post by Routy on 08/24/09 at 07:50:56

I read comments about all this stuff, and as usual, search didn't help.

Could someone explain,....or point me to info on this stuff ?

I know all about the past petcocks that had off-on- and reserve.
But the other day I ran outta gas and was confused about the pri and res position on the petcock. And is there a mod for this to make it more trouble free ? What was wrong w/ the old off-on-res system,...it was always foolproof I thought.
I have a very mechanical past, and I like to understand how stuff operates
so I can better trouble shoot it when the time comes.

Thanks for any help.
Rich

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by prechermike on 08/24/09 at 07:59:33

The stock petcock had on, prime and reserve. The thing was vacuum operated and the engine provided the vacuum. On was the standard position, reserve gave you a little more from the bottom of the tank. Prime was for when you ran out, took the tank off or something and needed gravity to prime the carb. It did nto require the vacuum. My diaprahm in the petcock went bad, so I replaced it with a raptor pecock, which is on-off-reserve.

I think that is the basic answer, if there is more, someone will chime in.

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by Duane on 08/24/09 at 08:39:25

There a a few diffrent fixes on the forum. The most common would be the raptor, but I read a post yestrday on here where some one converted the stock one to on/off/res.

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by verslagen1 on 08/24/09 at 09:19:46

2C2339223E382B29212F384A0 wrote:

I know all about the past petcocks that had off-on- and reserve.
But the other day I ran outta gas and was confused about the pri and res position on the petcock. And is there a mod for this to make it more trouble free ? What was wrong w/ the old off-on-res system,...it was always foolproof I thought.

"PRI" prime, for when you've run completely out of gas and need to refill the carb bowl prior to starting.
"RES" reserve, used when the main tank is empty, allows access to the bottom of the tank.
"ON" normal operation, res and on are vacuum controlled, when the engine is running, gas will flow.
Manual mod, basically, you plug 1 of the ports in the valve for off and remove the vacuum activated valve.

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by Serowbot on 08/24/09 at 10:38:18

2004 Yamaha 660 raptor petcock... Block off the vacuum line at the carb...
http://www.ronayers.com/browseparts.cfm?SearchString=5LP-24500-01-00&adv=5&kw=fiche.ronayers.com

or covert the stocker to manual...
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1113631600

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by Digger on 08/24/09 at 20:27:45

232C362D313724262E2037450 wrote:

....What was wrong w/ the old off-on-res system,...it was always foolproof I thought....

Yep, me too.

However, you needed to remember to shut off the petcock before walking away from the bike to prevent against a needle valve failure.

That, and I'm sure forgetting to turn the petcock on once getting underway has caused it's share of problems.

Still, I prefer to old, simple petcocks to the vacuum operated ones.

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by Routy on 08/24/09 at 21:52:43

Thanks for the info. I now understand its operation, and really,.... not a bad way of automatically shutting off a valve. But, as always, one more thing to give trouble when the components get aged.

Rich

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by voldigicam on 08/26/09 at 04:21:32

The original vacuum line hardens with heat and tends to quietly leak vacuum. I replaced with thicker fuel line, clamped at the ends. I have more confidence in that.

When I hit 100 miles on the tripmeter I change to PRI and run to a fuel stop. [bicycle speedometer trip meter]

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by Routy on 08/26/09 at 05:36:45

Quote:
When I hit 100 miles on the tripmeter I change to PRI and run to a fuel stop. [bicycle speedometer trip meter]
----------------------------------------------
A bicycle trip-o-meter,... what a great idea !

Rich

Title: Re: petcock-diaphram-vacum line-mod-etc ?
Post by PTRider on 08/26/09 at 09:50:30

Many models of bikes have a $25 kit available to rebuild the automatic petcock. Not so for our Savage/S40.

The ON and RESERVE are vacuum operated. PRIME is just gravity flow. Both RES and PRI come from the bottom of the tank...when you're out, you're out! ON takes fuel a short ways up from the bottom, so when it's out, you have some reserve fuel remaining to get you to a gas station.