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fuel leak from fuel switch.

Joined
Aug 5, 2009
Messages
6
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0
Location
Lewisville
First Name
Liz
Last Name
Patton
Ok. I've got a '91 Honda CB750 nighthawk. I've always noticed a gassy smell around the bike (I normally left the switch on) that stopped when I turned the fuel switch to off. I'd assumed it was part of a bike that I'd smell some gas. This morning I pulled off the cover to REALLY smell gas. I started looking around and noticed gas dripping (slowly, a drop every few seconds) from the fuel switch. I rode it to work ( :eek2: yes, I'm stupid - no need to restate the obvious) and it had all dried up. I turned off the fuel and it stayed dry. Rode it home with no obvious dripping, but left the fuel on while it cooled down and saw the barest drip from the area of the diaphragm cover on the back side of the switch.

What do I need to do to troubleshoot this, and/or try to fix this? I'm willing to try out my clymer, but I'd really rather not start doing major disassembly unless it's really needed - that bike is virtually my only way to work.


The only problems I've been having with this bike is getting it to turn over in the cold. I've been pre-heating the engine block by running hot water over the spark plug groove in the engine (learned my lesson about getting water on the carbs after I iced them open :eek2: ) I ride it 40 miles a day, 4 days a week to work. This is only the second day riding it after that nasty cold snap - and the bike was outside in it, but at least covered. Didn't notice any problems with the bike riding it to San Antonio for New Years.
 
I had this happen to my wifes Ninja 250. It was an easy fix. Just bought a new petcock assembly, drained the tank and put it in. It took about 30 minutes total and worked great. The part wasn't very expensive either. Less than $75 I believe.
 
I had this happen to my wifes Ninja 250. It was an easy fix. Just bought a new petcock assembly, drained the tank and put it in. It took about 30 minutes total and worked great. The part wasn't very expensive either. Less than $75 I believe.
Agreed, just did the same thing on my XR400. On the XR400 the petcock is very simple (no vacuum lines, just the one gas line) but it was a very easy install and around $50 if I remember. Checkout RonAyers.com
 
I had this happen to my wifes Ninja 250. It was an easy fix. Just bought a new petcock assembly, drained the tank and put it in. It took about 30 minutes total and worked great. The part wasn't very expensive either. Less than $75 I believe.

Depends on availability of the petcock. For my 82 Nighthawk 650, they run north of $125 on ebay or Bike Bandit. I'm living with the "no reserve" petcock for now.

The petcock assembly for a 1991 Nighthawk 750 is $182 on Bike Bandit. :eek2:

http://www.bikebandit.com/houseofmotorcycles/1991-honda-motorcycle-cb750sc-nighthawk-750/o/m1985

Or, you can put a Pingle petcock on (with adaptor) for less. Some people rebuild their bike's petcock, but I've heard that it often doesn't work that well.

Pretty easy install once you get the part. However, you should note that white teflon tape apparently does not work for sealing the threads (if that is needed).


Good luck,

Lee
 
I rebuild all of my petcocks on my vintage bikes.
 
We may need to talk! :trust:

The problem with Bikey's petcock is that it is riveted. I have another petcock that someone else rebuilt by drilling out the rivets, but I haven't tried it on the bike (it came with a spare tank I bought).

My petcock's problem is that (1) it doesn't have a working reserve, and (2) it doesn't really turn off all the way. With a working odometer and vaccum petcock thing, neither is a real problem (at least not $130 worth). :eek2:


I rebuild all of my petcocks on my vintage bikes.
 
The ones I am talking about you can purchase the parts, are you able to get parts for yours?
 
The ones I am talking about you can purchase the parts, are you able to get parts for yours?

Not directly. You can get parts that fit, but there is no kit made for my petcock because of the riveted construction.

I'm thinking of switching out for the rebuilt one to see how much it leaks adn if reserve works.

Or buying another bike with my tax return. :trust:
 
After talking with the older guy at Grifs (I love all those guys!) he suspects that due to the location of the leak and the construction of my petcock that it's the diaphragm that's leaking. So far it seems like just working the valve as though it was manual (aka, it's off any time I'm not riding it) is holding the leak at bay. I'll go talk to the honda dealer down the street and see if they can get me the petcock diaphragm assembly. Then on to removing the tank!:doh: I've never done that before so that may be fun...
 
Some of the guys on SOHC4-net remove the automatic valve (or route around it) and just use the petcock.


Lee

After talking with the older guy at Grifs (I love all those guys!) he suspects that due to the location of the leak and the construction of my petcock that it's the diaphragm that's leaking. So far it seems like just working the valve as though it was manual (aka, it's off any time I'm not riding it) is holding the leak at bay. I'll go talk to the honda dealer down the street and see if they can get me the petcock diaphragm assembly. Then on to removing the tank!:doh: I've never done that before so that may be fun...
 
You may be able to glue your diaphragm if it's just a hole unless it's deteriorated too far better to replace with new rubber.
 
I kind of want to have the parts before i start disassembling stuff, because it's pretty well my only transportation. In a worst case scenario I could only have that bike out of commission for a week - fridays are the only day I can't carpool with my hubby.

Right now it seems to be working well in 'manual' mode - on when i'm riding and off when i'm not.
 
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