Success! This took awhile, but the problem of disappearing gas is finally solved in my 1982 C70!
The problem was that the carburetor was "rebuilt" at some point, and whoever rebuilt it used parts intended for a 1980-1981 carb. Specifically they used the 1980-81 float valve with the black rubber tip. That is wrong. I replaced it with the correct float valve intended for the 1982 carb (shorter, no rubber tip), and that did the trick!
She runs like a charm now.
Thanks for all your help!
--- In Honda-C70@yahoogroups.com, richard jay <richardj4@...> wrote:
>
> A friend's C90 exhibited very similar symptoms a couple of weeks ago ---
> disappearing gas, no sign of leaks. Discovered a very high "oil" level. Changed
> the oil and turned off the petcock when the bike wasn't running. Problem
> solved. Later, he replaced the needle valve in the carb, which was the real
> problem, in that the old one had worn enough to permit gas to flow past it,
> eventually into the engine. Doesn't hurt to turn the gas off at the petcock when
> you're not riding.
> Rick
>
>
>
> ________________________________
> From: william belleau <wjbelleau@...>
> To: Honda-C70@yahoogroups.com
> Sent: Sun, October 31, 2010 3:45:52 AM
> Subject: Re: [Honda-C70] Re: Disappearing gas?
>
> Yes, it runs thru the intake pipe into the head, fills the head up and leaks out
> where it can. Past the rings, the exhaust valve seat into the muffler.
> I would change the oil as soon as you can.
> Bill
>
> --- On Sat, 10/30/10, demodevsells@... <demodevsells@...>
> wrote:
>
>
> From: demodevsells@... <demodevsells@...>
> Subject: [Honda-C70] Re: Disappearing gas?
> To: Honda-C70@yahoogroups.com
> Date: Saturday, October 30, 2010, 4:51 PM
>
>
>
>
>
>
> Thanks Bill. Sounds like I'll need to pull the carb and check it out. One more
> piece of info I discovered yesterday -- I have a small hole on the underside of
> the exhaust pipe, and while revving the engine, I noticed liquid sputtering out
> of the hole, making a mist pattern on the ground. It smelled like gas. Is this
> possible -- that gas can get all the way through to and come out the exhaust
> pipe?
>
> --- In Honda-C70@yahoogroups.com, william belleau <wjbelleau@> wrote:
> >
> > Check the oil level with the bike held upright and with the dip stick unscrewed
> >and just put into the hole.
> >
> > Is the oil level High?? I have seen carbs leak in such a way it runs into the
> >cylinder and past the rings into the crankcase.
> >
> > The normal leakage we see is the float with a hole in it or a stuck float or a
> >needle valve that is dirty or damaged and it runs out the carb overflow tube and
> >onto the engine or shop floor.
> > Bill
> > Portland OR
> >
> >
> > --- On Fri, 10/29/10, demodevsells@ <demodevsells@> wrote:
> >
> >
> > From: demodevsells@ <demodevsells@>
> > Subject: [Honda-C70] Disappearing gas?
> > To: Honda-C70@yahoogroups.com
> > Date: Friday, October 29, 2010, 1:04 PM
> >
> >
> > I bought a 1982 Honda Passport a few weeks ago. When I took ownership, it had a
> >full tank of gas. I've ridden the bike about 4 miles, but today I noticed there
> >is only about half a tank of gas.
> >
> > The bike had a previous gas leak, either from the carb or the petcock valve.
> >But now I don't see any obvious leaks from those places. Instead, the carb
> >overflow drain is wet with a small amount of gas and the exhaust valve cover (at
> >the bottom of the engine) has a drip of gas on it after riding. However, no
> >puddles or major out flowage of gas are showing. The bike does smell of gas
> >before, during, and after riding.
> >
> >
> > Any ideas as to where all the gas is going? Would a hole in the float AND a bad
> >petcock valve that won't shut off cause this?
>
1970-73 C70 Honda Service Manual: http://tinyurl.com/6ebwtw
1970-73 C70 Troubleshooting Guide:
http://tinyurl.com/6ebwtw (scroll to sec.7.1 page 101.jpg)
1980-83 C70 Honda Service Manual: http://tinyurl.com/hu42c
1980-81 C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec.18-1 page 170.jpg)
1982-83 C70 Troubleshooting Guide:
http://tinyurl.com/hu42c (scroll to sec. 20-28 page 205.jpg)
1980-81 C70 Maintenance Schedule: http://tinyurl.com/z4zn6
1982-83 C70 Maintenance Schedule: http://tinyurl.com/hw35c
More resources for C70 Passports and Cubs:
http://www.shlaes.com/Vehicles/Scooter.htm
http://www.velodrome.com/HondaC70/HondaC70.html
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