Rebuilt petcock leaking

General forum on engines, transmissions, gearing and modifications to each

Moderator: rztom

Post Reply
Message
Author
User avatar
Consciousness
Posts: 409
Joined: Sun Jul 21, 2013 12:28 pm
Location: The Big Apple

Rebuilt petcock leaking

#1 Post by Consciousness » Sun Nov 16, 2014 10:23 am

Hi all, I have noticed a puddle of fuel and a drained tank since the cold weather hit, I have recently rebuilt the petcock with a kit from economy and it was working fine in the warm weather, any ideas as to what's going on?

Thanks
85 RZ350 KR. Racetech/Fox Motul 10W. Telefix, Prog. Zeel, VForce4's, VM30 Mik's Uni-Filters & UFOs, Grooved Head & Mild Port w/Boyesen's by Rich's Taylor'd Porting, Orig. Toomeys, Redline, Conti Attack2.

mkane
Posts: 921
Joined: Wed Feb 20, 2013 11:43 pm
Location: Cloverdale, CA

Re: Rebuilt petcock leaking

#2 Post by mkane » Sun Nov 16, 2014 10:32 am

Do the petcock mod and get rid of the vacuum port.

User avatar
Consciousness
Posts: 409
Joined: Sun Jul 21, 2013 12:28 pm
Location: The Big Apple

Re: Rebuilt petcock leaking

#3 Post by Consciousness » Sun Nov 16, 2014 2:28 pm

Thanks mkane, nice that I can keep the stock fuel dial, that was the reason I went the rebuild route over the pingle. Here's the post just in case others need it http://www.usa2strokers.com/forum/forum ... dification
85 RZ350 KR. Racetech/Fox Motul 10W. Telefix, Prog. Zeel, VForce4's, VM30 Mik's Uni-Filters & UFOs, Grooved Head & Mild Port w/Boyesen's by Rich's Taylor'd Porting, Orig. Toomeys, Redline, Conti Attack2.

hondaror
Posts: 2828
Joined: Mon Mar 03, 2014 8:44 pm
Location: Alberta, Canada

Re: Rebuilt petcock leaking

#4 Post by hondaror » Sun Dec 28, 2014 10:07 pm

Great mod. Suggestion, don't relabel the petcock so potential thief's/joy riders have no clue what they are doing.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

joolstacho
Posts: 28
Joined: Thu Sep 06, 2012 5:12 am
Location: Melbourne

Re: Rebuilt petcock leaking

#5 Post by joolstacho » Fri Jun 26, 2015 5:37 am

I have a leaking petcock. I've tried rebuilding it, cleaning it etc, I've added a little more tension to the wave washer, there's no damage or wear evident, and whilst at first it looked hopeful, after a run, I've found it still leaks. A new petcock is too expensive. I've read bad reviews of the repair kits that are available (?). I see the inline fuel tap (Briggs and Stratton -ouch!) option. Nice, cheap and cheerful, -It may come to that.
Regarding this mod:
http://www.usa2strokers.com/forum/forum ... dification" onclick="window.open(this.href);return false;

Removing the vacuum system obviously this works for some people, but can someone explain why/how it works? Surely if the petcock leaks it must be caused by the rubber seal gasket and or a weak wave washer that 'makes' the seal, irrespective of the vacuum line? How does bypassing the vacuum line fix the leak?

joolstacho
Posts: 28
Joined: Thu Sep 06, 2012 5:12 am
Location: Melbourne

Re: Rebuilt petcock leaking

#6 Post by joolstacho » Mon Jun 29, 2015 12:58 am

Well I've tried something else which has worked (SO FAR !) - but I'm getting an in-line on-off tap anyway, - Festo brand 6mm inline ball-valve which are used in industrial applications and model jet turbine aircraft applications, so should be good quality. So anyway, I pulled the tap backplate off, which gives access to the fine spring that holds the vacuum plunger which has the small o-ring into the aperture which stops fuel flow. I thought maybe if the spring has lost some tension it might fail to hold it with enough pressure to seal the hole. So I gently pulled the spring to lengthen it a bit. Reassembled, and it works well so far, -it's stopped the drip from the fuel tap outlet.
BTW a mate of mine has converted plenty of fuel taps, and instead of Lumiwelding, he drives in a suitably sized bearing ball into the hole to blank off the vacuum.

Speed Freak
Posts: 26
Joined: Fri Apr 18, 2014 8:17 am
Location: Spielberg (Austria)

Re: Rebuilt petcock leaking

#7 Post by Speed Freak » Thu Jul 23, 2015 5:55 am

Seems that it is a common problem...

I have also rebuilt my petcock but it`s still leaking - Checked everything, vacuum valve seat is in good condition.
Combined with slightly leaking needle valves it leads to fuel on the garage floor.

I think the problem is the O-ring of the vacuum valve.
There are differend hardeness grades available, maybe the rebuild kits use too hard standard O-rings for the vaccum valve.
Problem: It needs more force to seal, but a stronger spring would be a risk because it may not open with the available vacuum.


Maybe i will try a softer o-ring in future, but at the moment the additional in line fuel tap from a Honda lawn mower works good :)
By the way - at the moment there are temperatures from 25-36°C (night/day) in Austria - some days ago i forgot to close the lawn mower fuel tap, but there was no fuel on the floor in the morning.
Seems that it also works fine on my bike as long as the temperatures are high enough.
My Bikes:
Yamaha RD500 1985
Yamaha RD350 1985
Yamaha R1 2001
Honda CBR 1000 2006

ief
Posts: 82
Joined: Wed Jan 06, 2010 8:08 am

Re: Rebuilt petcock leaking

#8 Post by ief » Wed Aug 26, 2015 2:13 pm

Guess I took a shortcut, just removed the plastic 'spacer' bit, made one screw shorter, put back together, seems good, only have pri, fine with me.
O no, red pilled.

User avatar
Evans Ward
-----
-----
Posts: 1546
Joined: Sun Jun 07, 2009 6:39 pm
Location: Macon, GA

Re: Rebuilt petcock leaking

#9 Post by Evans Ward » Wed Aug 26, 2015 6:35 pm

Silverstrom/ John gave me a tip some time back- save yourself the time and trouble of rebuilding which may still leak and buy a new petcock still available from Yamaha. Peace of mind and no leaks!
84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

OzRz
Posts: 1
Joined: Sat Jun 24, 2017 11:13 am

Re: Rebuilt petcock leaking

#10 Post by OzRz » Wed Jul 12, 2017 11:14 am

Can someone tell me the dimensions of the diaphram spring including wire sectional thickness? thanks

joolstacho
Posts: 28
Joined: Thu Sep 06, 2012 5:12 am
Location: Melbourne

Re: Rebuilt petcock leaking

#11 Post by joolstacho » Wed Jul 12, 2017 8:31 pm

The links to the 'petcock shutoff modification' are u/s, and nothing relevant by that name comes up in a search,
Can anyone give us a link to the instructions please?
I just blanked off my vacuum line and use PRI for on and any other position as Off.
But there's no reserve with this setup, maybe there is there a better way?

75RD350rider
Posts: 601
Joined: Thu Jun 19, 2014 9:52 pm

Re: Rebuilt petcock leaking

#12 Post by 75RD350rider » Thu Jul 13, 2017 4:55 pm

viewtopic.php?f=21&t=13677" onclick="window.open(this.href);return false;

Here is how I fixed mine and it works like a champ....RD 400.petcocks are cheap and available....sorry the pics are.gone with the demise of photo bucket...
I love the smell of Blue Marble in the morning!
Tim Steele in Front Royal, VA

Post Reply