Fuel leak at petcock

[Papa Fred]

Looking for ideas here on a possible cause of fuel leaking (seeping) past the clamps on the fuel line at the petcock on my 2000 RSV.

I replaced the old line a couple of years back and till a few weeks ago didn't really notice any issues.  What got my attention was the fuel stain on the front left cylinder fins and the dog-bone.  When parked for a short time I have been leaving the fuel on...when stopped for the day the fuel is off.   Recently, when parked with the fuel on or off, gas is weeping out past the clamp.   Thinking the hose I replaced was a cheap grade or something, I replaced it with a more rigid hose from the petcock back to the filter (in-line under the seat..installed a couple of years ago) then from the filter down to the OEM pump.  The pump appears and sounds to be working fine.

I've tried regular screw clamps, the spring-type clamps, a type of fuel injection line clamp...all with no success at stopping the leak.  I tried tightening down a clamp on a spare piece of the new hose as well as the one I pulled off.  Both seem to distort slightly when under clamp pressure, and I got to thinking that I may have created the problem by using a heavier hose than I need.  The new hose is a good snug fit over the flare on the gas pipe coming out of the petcock, so I figured a clamp would be insurance.

I'll mention here that I pulled the hose off the petcock to see if the petcock was leaking.  Bone dry when turned off.    Also, the vent line at the top of the tank is clear...blew compressed air thru with no restriction.

I noticed a couple of times when I removed the fuel line there was enough pressure in the line to blow gas out of the hose. I thought that some type of back pressure in the carbs was forcing the gas back up the lines,  but with the pump being effectively closed when the power is off, that seems odd if even possible.

Anybody have any ideas , or experience, with this.    I've noticed on other bikes the fuel line at the petcock is held in place by that simple spring clamp.  Could it be as simple as installing a thin rubber tube instead of the heavy-duty stuff??

Thanks in advance, gang.  It'll be interesting to see where this goes.

 

Cheers...

 

[Squidley]

I have seen on several occasions where the actual brass tube, that the hose slips over, will come loose. I've actually pulled mine out a couple of times trying to remove the hose from the peacock. I would check and make sure that the brass tube is completely seated in the body 0.02

[Marcarl]

If you have fuel coming out with the petcock off, I would be checking above the petcock real close. Could be that the petcock doesn't shut things off completely, but I would think the petcock seal to the tank??

[Papa Fred]

Thanks for the reply Carl...

 

When I pull the gas line off, there isn't any fuel coming from the petcock itself... either around the seal to the tank, or the outlet...with the fuel valve shut. It only weeps out around the hose when in use.  If I shut the fuel off and let the bike run for a couple of minutes to use the gas  in the line, or it sits overnight and cools down, there is no leak. 

I'll be doing a bit more research today into the fuel line I'm using.  Maybe it's a simple solution. 🤞

[Patch]

A couple of points to offer up:

The tubing must match the size of the nipple shaft

the tubing should be curved in a way that allows for vibration and expansion/retraction

the reason for spring clamps is because the are round, gear clamps are not, fuel clamps are

I change the O-rings on the 91 petcock and I was not one to use it. I set mine to RES and leave it use gas rated O-rings

The only pressure on the petcock in the weight of the fuel above it

The 4-6 lbs the pump produces id between the pump and the float valve/needle

 

[Papa Fred]

Thanks for those points, Patch. 

I figured the pump pressure didn't really factor into the fuel seeping out at the petcock, unless it was somehow allowing some sort of back-pressure to make its way up the line. I double (triple?) checked the petcock itself to eliminate it as the problem..zero leakage from around the tank seal or the fuel nipple into the petcock ( I've seen a few posts about those coming loose).  As for the tubing itself, I've got a pre-formed piece of plastic tubing with a 90 degree bend that slips over the fuel line and curves it from the nipple inboard under the tank.  From there the line takes a gentle turn toward the back. 

Your mention of the tubing size got me thinking, however.  When I originally replaced the line a cpl years back, I probably used the old line as a guess for the new tubing.  Being old and worn out, it was likely a bit larger ID than required.  I'll measure the fuel nipple and get something that needs to stretch a bit to slip on.  That way the spring clamp is just insurance, not defence.

Thanks for the memory jog...

Cheers

[Patch]

thats the idea Fred the spring clamp bites and tracks with the tubing but only as far as the flare, at which point the temper of the clip stops progression

Little things can be such a nuance EH 

[Papa Fred]

Our typically polite Canehdian way to describe a royal PITA!  😏 😎

I'll be looking for less rigid gas friendly hose tomoro...hopefully have a positive result to share.

[Patch]

Well yaknow Carl has been working on my english side for a while now; its at the point he has me rolling or counting beads, or, kneeling on potato peels 

[Marcarl]

32 minutes ago, Patch said:

Well yaknow Carl has been working on my english side for a while now; its at the point he has me rolling or counting beads, or, kneeling on potato peels 

Montreal didn't win!!

[Patch]

Yabut they plaid!

[luvmy40]

But what is their Tartan?

[Patch]

"It's said that red tartan was worn in battle so blood would not show"

[Marcarl]

On 7/13/2021 at 2:25 PM, Patch said:

"It's said that red tartan was worn in battle so blood would not show"

So did Montreal bleed a lot?

[rollingjones69]

On 7/12/2021 at 8:00 AM, Squidley said:

I have seen on several occasions where the actual brass tube, that the hose slips over, will come loose. I've actually pulled mine out a couple of times trying to remove the hose from the peacock. I would check and make sure that the brass tube is completely seated in the body 0.02

Is there some kind of sealant that needs to be used when putting tube back? I pulled mine out last night while trying to separate hose for tube and was thinking I would have to replace petcock assembly. Thanks in advance

[Squidley]

17 hours ago, rollingjones69 said:

Is there some kind of sealant that needs to be used when putting tube back? I pulled mine out last night while trying to separate hose for tube and was thinking I would have to replace petcock assembly. Thanks in advance

I never put any sealant on it, but obviously it would have to be something impervious to gas. I just took a small rawhide hammer and "lovingly" tapped it back in. The brass is soft enough that it will usually swedge itself sealed.

[Papa Fred]

I just saw this addition to my original post.....apologies if my "fix" got forgotten.  The small brass tube coming out of the petcock was loose.  I cleaned it thouroughly, then applied a VERY thin smear of JB Weld to the pipe (tube) and gently tapped it into place.  The JB squeezed out around the tube to form a perfect little "donut" seal around the tube.  Several thousand miles later and no issues with fuel leaking.