1982 Honda CB750 shuts off

Got one at home that'll start, idle for a few seconds, and simply shut
off afterwards. Then when I try starting it again, it may or may not
start. I can try and try until the battery dies... the next day, I'll
try again, and after the first attempt, the engine runs, but shuts off
a few seconds later. Same routine... any ideas on what to check? Could
it be a starter relay problem?

 

go thru the fuel supply system, the strainer, etc.
remember, there's a little strainer in the gas tank inlet to the fuel
valve.
sounds like it may be seeping a carbset full of fuel and then running out
of fuel at idle.

of course, you have checked for spark after the engine has stopped,
haven't you?
if i recall, the ignition consists of two separate coil and point sets so it
should still run somewhat on one coilset, although not well.
fuel is my guess.
good luck, sammmmm

 

fuel starvation

 

Most likely problem? Fuel supply.
2nd most likely issue? Fuel supply.
3rd most likely? Fuel supply
..
..
..
10th most likely issue? Fuel supply.

Drain the fuel bowls. Put some Berrymans in the tank let it sit for a few
hours. Start it and run it until it quits. Let it sit over night. Start
it again and run it until it quits. Let it sit overnight.

Don't keep trying to start it running down the battery. You might cook the
starter motor. Then you will be buying a starter on top of everything
else.

 

One potential contributor to the "fuel supply" problem would be clogged
venting for the tank. Like any bottle of liquid, if air can't get in, liquid
won't long pour out...

 

True, but I would expect it to run at an idle for longer than a few
seconds.

 

One potential contributor to the "fuel supply" problem would be clogged

Try starting it with the fuel cap off and see what happens... at least
that way , if it does the same thing, you can rule that out....to me though,
it sounds like a clogged fuel filter, or petcock filter (if you have one).
If you can see little metal chips in the fuel filter, the inside of your
tank is starting to rust, which means its time to Kreme it. You may also
have those little rust particles in the carb already, so those would have to
be cleaned if you haven't already done so.
One question is how old is the gas? It may be contaminated (with water)
and need to be drained.

Let us know how you make out..

Fwed

 

I think that Kreme is not the best product. I belive that POR-15 is
better. If any coating is to be used in the tank, follow the instructions
to the letter.

I didn't coat mine but I did use Marine Clean on it. Amazing the junk that
came out.

 

These bikes have a very large, fine mesh screen in the intake from the tank,
the tank would really have to be in amazingly sad shape for particles to
clog that screen. It is only a moments work to pull the fuel line off the
petcock
and put on a temporary rubber line, and look at fuel flow from the tank

Ted

 

When I took the petcock off my 81 Honda due to lack of fuel flow, it was
nearly completely clogged with varnish. That is what happens when a bike
sits for several years with fuel in the tank. The tank? Once I cleaned it
it was fine. No kreem or POR15 needed. I did however add a fuel filter to
the mix.

 

In my particluar case, I was getting small chips, so the tank needed to
be coated.....at the time there was a new tank on ebay, but was wayyyyyyyyyy
too much money.... my bike sat for 6 yrs. and so the story goes.. or went in
my situation... now the bike runs great.... probably the best its ever
ridden because ive rejetted it and it doesn't even have any hesitation in
the 5-6000 rpm range anymore!!

Fwed

 

All the help is greatly appreciated. Thanks everyone.

The gas in the tank is from last year, and I want to drain it
completely. I bought a fuel additive by Lucas that I want to put in the
tank once all the fuel has been drained. I managed to drain residual
gas by loosening a screw on each side of the bike near the carburetors.
Question: how do I remove ALL the gas from the tank?

Paul

 

You could remove the petcocks, but that's probably overkill.

Put the petcock on "start" or reserve, drain what you can,
put a little bit of new gas in the tank and drain again.

Easiest way to dispose of the old gas is to mix with a
tank of new gas in your car.

 

Fweddybear did not write the above... not sure why people cut and paste....

Fwed

 

Pull off the tank, remove the petcock, and if your lucky the plastic
screen will come out too. Otherwise carefully thread a wood screw that is
a bit bigger than the screen down into the screen just enough to grab it,
then gently wiggle and work it out. With the screen in the tank it will take
forever to
drain it.

Ted