Honda 350/450 petcock leak - Motorcycle Forum
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post #1 of 8 (permalink) Old 05-16-2011, 10:30 PM Thread Starter
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Honda 350/450 petcock leak

This looks to be a simple fix but is starting to become an annoyance. The fuel petcock leaks pretty much on any setting. I ordered a new interior four hole rubber fuel gasket and replaced the two valve screws (stripped heads).

Inside, I found it already had a brand new rubber gasket. Evidently installed by the previous owner, he stripped the screw heads putting it back together.

I'm beginning to see why.

The system itself seems a masterpiece of simplistic engineering. The rubber fuel gasket seats into the receseed valve body. The valve itself doesn't press up uo against the rubber gasket but up against the valve body the gasket is recessed into. This keeps the valve handle from wearing against the rubber gasket when it's rotated.

Pressure is applied to the valve handle by a "warped" spring washer placed between it and the outer faceplate. Screw down the faceplate and the warped washer applies pressure to the valve handle, bringing its surface flat to the four hole fuel gasket.

The previous owner tried to fix the leak with a new gasket but it still leaked on "Reserve". In his attempt to increase pressure on the valve, he stripped the screws.

Well! I've now had it apart about forty times now and nothing seems to change. It leaks at the valve and not at the drain bowl or tank compression fitting. It leaks at its worst when turned.

I have felt with my finger to see if the four hole gasket is seated all the way in. It seems to be but this remains my biggest suspicion. I've tested a rubber "O" ring in place of the warped washer for more pressure and this does stop the leak but that "O" is too thick and I know it won't last long with that valve turning against it.

So what's the trick here? What obvious thing am I missing?
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post #2 of 8 (permalink) Old 05-18-2011, 05:47 PM Thread Starter
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Well! I put the "O" ring back under the faceplate and it puts enough pressure on the valve to stop the leak. Of course, every time I turn that petcock lever I'm wearing that rubber so it will start leaking again eventually. I tried to increase the bend in the spring washer but it looked the same after as before.

Am not looking forward to paying $ 45 plus shipping for a new one.
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post #3 of 8 (permalink) Old 05-19-2011, 09:07 AM
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All you really need that petcock for is to adapt the fuel line to the tank threaded fitting. I got frustrated fixing mine,so I fixed it one final time and then added a cheap plastic lawn mower petcock right below the OEM and also a tiny clear fuel filter. I can see at a glance that the fuel is flowing through that filter and I like it that way
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post #4 of 8 (permalink) Old 05-19-2011, 10:37 PM
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Pingle makes a aftermarket petcock for high performance bikes, its high quailty and simple but they dont fit all tanks and you will have to add a filter.
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post #5 of 8 (permalink) Old 05-19-2011, 11:11 PM Thread Starter
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Well! The "O" ring was dripping gas in the "Off" position so I took it apart again for the 50th time. Based on a few things I'd scoured over the net, I took the face plate and put it in a vice to flatten it, then pounded both sides with a hammer to get it as flat as possible. I then added a second "wave" washer to the first, rotated it to where it was offset enough to create six pressure points instead of three, and put it all back together.

At first no leaks. But then it later leaked on "Reserve". So I frigging torqued those screws while it was still dripping until it stopped (at absolute "max" tightness). Right now it's not leaking. Can't say for how long but it's my last try to fix that valve. If it leaks again, another one is going on.

Now I probably have to clean the carbs too. Who knows what I flushed through the lines on all those assemblies and reassemblies.
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post #6 of 8 (permalink) Old 07-03-2011, 04:42 PM Thread Starter
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I gave up!

Well! It started to not completely shut off in the off position, dripped gas in my garage and ruined the AMSOIL in the crankcase. I gave up and, for $ 49 bought a new one (Looked at some $ 25 cheapies but they were out of stock.).


Removing the old one revealed it had no reserve pipe (hence, no filter screen). I was lucky and not one bit of rust came out of the tank on flush. I'm glad I replaced the valve after seeing that.

The new valve turns much harder than the old (They are identical.) which suggests to me the faceplate on the old one wasn't putting enough pressure on the new rubber gas gasket underneath. Although an incredibly simple design, there's no way to add enough pressure without adding a second wave washer or an "O" ring.

At the price of motorcycle oil I wasn't going to keep trying to fix it. I replaced it.
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post #7 of 8 (permalink) Old 07-13-2011, 08:43 PM
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Quote:
Originally Posted by Dumcoach View Post
Well! It started to not completely shut off in the off position, dripped gas in my garage and ruined the AMSOIL in the crankcase. I gave up and, for $ 49 bought a new one (Looked at some $ 25 cheapies but they were out of stock.).


Removing the old one revealed it had no reserve pipe (hence, no filter screen). I was lucky and not one bit of rust came out of the tank on flush. I'm glad I replaced the valve after seeing that.

The new valve turns much harder than the old (They are identical.) which suggests to me the faceplate on the old one wasn't putting enough pressure on the new rubber gas gasket underneath. Although an incredibly simple design, there's no way to add enough pressure without adding a second wave washer or an "O" ring.

At the price of motorcycle oil I wasn't going to keep trying to fix it. I replaced it.
What bike do you have? I am in the process of Red Koting the inside of my rusty tank on my 1978 Honda 400a. I also had a leaky petcock. I replaced ONLY the O-ring at the tank seat so far. Now that I read your thread I may end up needing to do what you did (new one) if the leak isn't remedied.

Do you know if all those older Honda's have screens inside of the tank at the petcock?? I cannot tell if mine has one? Shining a light up there seems to show that there is nothing in there. (screen)
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post #8 of 8 (permalink) Old 07-15-2011, 05:54 PM
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My CB350, 1968, does.


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