Unstoppable Fuel Leaks!!! (LONG)

[SlowOldGuy]

While doing a little winter cleaning on the '85, I ran across a few problems that took a while to sort out and I'd like to share the lessons learned.
 
After pulling the lower fairing off, I noticed a strong smell of gasoline and saw a slight wet area under the center stand.  A closer look revealed dripping out of one or more of the small carb hoses.  Off comes the tank to expose the second problem; the only-a-few-years-old petcock is no longer shutting off the flow of fuel completely.  

I pull the carb bank and set it up on my bench with an aux fuel source.  After about an hour, fuel starts to drip from 2 of the small choke circuit hoses (cylinders 1 and 2).  I drain and pull the bowels on all 4 carbs.  Nothing looks out of place, passes the upside down blow into the inlet hose test so the needles and seat o-rings appear to be okay.  Thinking the 25 year old floats may be getting a little saturated, I adjust the float tang down slightly to compensate.  Back together and hooked back up to the fuel supply, the drip comes back after about an hour.  

I change the float in the #2 carb and it stops leaking.  The #1 carb, however, still drips.  I try 2 other floats with no success.  I think: "I can't have that many bad floats."  So I swap the float with the #4 carb (which doesn't leak) to see if the drip will follow the float.  It doesn't, still leaking on #1 after sitting about an hour.  

Must be the needles or seat o-rings.  Install new o-rings in all carbs and #1 still drips.  Interruption here to address the petcock leak.  I install a new 5mm ID x 2mm X-section o-ring on the plunger and the petcock continues to leak.  Change to a stiffer spring and still leaks.  Try a 5mm x 1.5mm o-ring and still no change.  Strong spring, stock spring, 5mm x ?o-ring, nothing seems to stop the relentless leaking.

This is beginning to get frustrating.  I can't stop the flow of fuel from anything!
Back to the carbs.  I have a brand new set so I start stealing parts from that assembly.  First try a float.  Still leaking.  Perform massive float adjustment, no change, still leaking.  Next I swap the needle seat, still leaks.  Add a new needle, still leaks.  Okay, this is past the point of ridiculous.  It is not the needle, seat, o-ring, float or float height, what the FLOCK could it be??

Back to the petcock.  Having tried every size of 5mm o-ring in existence and all kinds of different springs I'm rapidly running out of ideas on this leak also.  I dig up the Kawasaki part numbers for their o-ring and spring and head over to the local K dealer.  Unfortunately, it's New Year's Eve and they're closed for the next 3 days.  Swing back by on Monday and show the number to the heavily tattooed girl working the parts counter (yikes!).  "That part number is not in stock, what year is it from?"  Of course, I have no idea so I ask her what the part description says.  She gives me a puzzled look and says: "4mm o-ring."  A 4mm o-ring?  DING! DING! DING!  Back to the hardware store where I procure one of every 4mm o-ring they stock.  Which is only 2 sizes, a 4mm x 1.5mm and x 2mm.  The 1.5mm o-ring fails miserably with any combination of springs.  The 2mm, however, has been holding for 2 days now!  

By now, my garage smells like a refinery.  I have to air it out every night to get the fumes out.  I hesitate before turning on the lights for fear that I'll blow the roof off.  

Having finally stemmed one gusher, it's back to the carbs again.  I pull the needle seat out of the #1 carb hoping to see a crack in the carb body.  By now, this is the only thing that can possibly explain why this carb is still leaking fuel.  As far as my 53 year old eyes looking though 2 magnifying glasses stacked on top of each other can tell, there's no crack in the area around the seat.  However, I do notice that the internal bore of the seat hole is really rough looking.  It appears that there wasn't much "extra" material there during the original machining operation.  The finish may have degraded slightly over the last 25 years to where the seat o-ring no longer seals.  This would also explain why it takes about an hour before the leak appears.  The seepage past the o-ring is very slight and it takes time for the fuel level to reach the hose outlet.  I've swapped to a different carb body and so far no more leakage.  I'm going to attempt to re-finish the seat bore in the original carb body to verify that is the problem.

I spent my entire year end vacation jacking with this bike.  At least I hope that I learned a few things, which I'll now share.

First, it appears that a 4mm ID x 2mm cross section o-ring is needed on the old style petcocks.  Previously I recommended a 5mm o-ring, but I could not get the leak to stop using a 5mm.

On a carb leak, if fuel is slowly dripping from one or more of the small hoses, it's probably gas seeping past the needle or the seat o-ring, or a crack in the carb body, or a bad finish on the body casting causing the o-ring to not seal effectively.

If you've got a gusher leak that's blowing fuel out of the larger overflow hoses, then it's probably a stuck float or trash between the needle and seat.

DavidR.

[Pat Conlon]

"...... I'm going to attempt to re-finish the seat bore in the original carb body to verify that is the problem....."

Wow, David. You've been thru the ringer on that one....Kudos for identifying and attempting to fix the problem(s). I would have just thrown away the offending carb body. That's why *you* are our official FJ carb guru and we are very fortunate to have you with us.

Please report back on what you did to refinish the carb body float needle seat bore. I wonder if you can get a small diameter honing brush in there and, if so, then will you a bigger cross section O ring to compensate for the slightly larger bore? If so, then would this thicker O ring fit the groove on the barrel of the needle seat? So many questions....I'm glad that you're doing this and not me.....

Also...Thanks for the advice on the 4mm ID x 2mm O rings for our 84/85 vacuum petcocks. Good to know.

This is good stuff, if you don't mind David I would like to copy and paste your post over to our Carb Files section...Ok with you amigo?  Thanks  Pat

[racerman_27410]

David,

Sounds like an ordeal (to say the least)

Good onya fer not blowing up the garage and or losing your mind!   

Time for a ride now!


KOokaloo!

Frank

[RichBaker]

Lots o' work, good results...  a quick tip on floats: Weigh them... if one's leaky, it'll be heavier than the others.

[SlowOldGuy]

Hey Pat,
No problem on the copy/paste
.
I should also mention that I'm re-doing the factory fuel plumbing.  I've managed to get one of those quick disconnects installed such that it doesn't kink the lines with a stock airbox. I'll take pictures when I'm finished.

I've also been eyeing an electrical fuel shutoff solenoid.  So far there's not enough room, but it may be possible for those of you who have gone with the UNI Pods.  I may have to get me a set of the pods to play with.  I thought I would need the solenoid if I couldn't fix the petcock.  With the success of the 4mm o-ring, the priority on a solenoid has gone down considerably.   But I've got one with 1/4 NPT ports identified that I may go ahead and purchase just to have on hand.

Just out of curiousity, anyone know if the 86/87 shutoff solenoid petcock could be used for this function?  Was it a normally open valve that would close upon power application?  If so, then nevermind, it would not work for what I want.

I'll update on the bore re-finish.  I'm going to try to smooth it up with 600/1000 grit first or polish it with a small Dremel buffer bit and metal polish and see if the regular o-ring will still work.  I use a slightly over-sized 7x1.6mm o-ring but somewhere I've got a bag of 7x2mm o-rings in case I need to try one of those.

Rich,
Thanks for the float weighing tip.  I need to dig up my reloading powder scale.  It should be sensitive enough to detect any difference.

DavidR.

[Pat Conlon]

"....Just out of curiousity, anyone know if the 86/87 shutoff solenoid petcock could be used for this function?  Was it a normally open valve that would close upon power application?  If so, then nevermind, it would not work for what I want.

I would be surprised if it was normally open. If I understand it correctly, that would mean that to close the valve (shut off the gas) you would have to energize the solenoid drawing power from the battery. Lose power to the solenoid and the valve opens and gas flows? Like a dead battery?
Naaaa,  That doesn't sound right. (or safe)

[Dan Filetti]

I would be surprised if it was normally open. If I understand it correctly, that would mean that to close the valve (shut off the gas) you would have to energize the solenoid drawing power from the battery. Lose power to the solenoid and the valve opens and gas flows? Like a dead battery?
Naaaa,  That doesn't sound right. (or safe)

I thought the same thing Pat.  FWIW.

Dan

[racerman_27410]

 86/87 was actually an electronic reserve petcock.   the "reserve" valve is spring loaded in the open position.

upon getting low enough on fuel (how low no one actually know)  the electromagnet is energized to pull the piston in which blocks the flow of fuel.. simulating (my ass) running out of fuel.  flipping the reserve switch just breaks the circuit so the spring can push the piston back open allowing fuel to flow again. (and you go on about your merry way)


dont think it would work as a fuel shutoff as it would drain the battery while the bike was parked.

Kookaloo!

[SlowOldGuy]

dont think it would work as a fuel shutoff as it would drain the battery while the bike was parked.

Thanks, Frank.  That's how I thought it worked.  Too bad, if it worked backwards, it would be a perfect solution to the bad petcock problem.

DavidR.

[Pat Conlon]

Huh? If the petcock is in the normally open mode what's to keep gas from filling your carbs and engine when the bike is shut off?
Oh, wait a minute....these bikes have fuel pumps. The pump is off. Duh.....nevermind, carry on..

[SlowOldGuy]

Nope, in addition to the (simulated reserve) solenoid, they also have the vacuum shutoff.

DavidR.

[Pat Conlon]

Oh. So then the petcock is normally closed (no vacuum) It's the solenoid that's normally open. Ok. Thanks David.

[Travis398]

I spent my entire year end vacation jacking with this bike.  At least I hope that I learned a few things, which I'll now share.

First, it appears that a 4mm ID x 2mm cross section o-ring is needed on the old style petcocks.  Previously I recommended a 5mm o-ring, but I could not get the leak to stop using a 5mm.

On a carb leak, if fuel is slowly dripping from one or more of the small hoses, it's probably gas seeping past the needle or the seat o-ring, or a crack in the carb body, or a bad finish on the body casting causing the o-ring to not seal effectively.

If you've got a gusher leak that's blowing fuel out of the larger overflow hoses, then it's probably a stuck float or trash between the needle and seat.

DavidR.

sounds like it was pretty frustrating, glad you was finally able to solve the problem, and thanks for passing on the info.