yamaha 1973 GT 80

please can anyone help ? i have a 73 GT 80 has carb prob.! keeps
fouling plug ! need help with setting air/fuel/mix also oil injector
system bypassed ! fuel/oil premixed THANKS

 

Well, you might be pre-mixing too much oil with your gasoline.

I didn't know how much ordinary motor oil would be enough in my first
two stroke, so I mixed about a 3 to 1 ratio, and that was an awful
mess.

One quart of oil in five gallons of gasoline is a 20:1 mixture and
that's plenty of mineral oil for larger 2-strokes, like 250cc engines

You can mix automotive mineral oil about 32:1 in an engine that small
and have no problems except for excess smoke, or you can mix a
synthetic 2-stroke oil about 50:1...

The idle mixture screw is an air screw, so turning it counterclockwise
lets more air into the idle mixture.

About 2-1/2 turns out is about as far as you'd want to go, and you have
to be careful that the screw doesn't get so loose (it has a spring
under it to keep it sort of tight) that it falls out, and you'd have a
hard time finding another screw.

Your problem might not really be an adjustment problem, it may be
caused by an accumulation of premix in the crankcase.

The fouling problem may be caused by a sticky float valve in the
carburetor or a leaky petcock with a sticky float valve.

Even if you shut the petcock off every night, it might still leak, and
enough premix could leak past the sticky float valve and run down into
the crankcase, and then everytime you try to start the engine, it
throws a bunch of excess oil onto the spark plug and it immediately
fouls.

Excess premix oil tends to build up in the crankcase anyway. The hot
engine evaporates whatever gasoline is left in the crankcase when you
shut it off, but the oil doesn't evaporate, it accumulates.

European 2-stroke engine designers knew about the problem of oil
accumulation, and they designed engines that had drain plugs underneath
the crankshaft so owners could drain the accumulation out of the
crankcase. I'm NOT talking about the transmission oil drain plug.

Suzuki is the only Japanese manufacturer that ever had those plugs
underneath the engine. That was on the T-500 Titan. There was a large
slot-headed screw under each cylinder.

Then they came up with the idea of having each adjacent cylinder suck
the excess
oil out of its neighbor cylinder through a small diameter rubber tube,
but that never worked worth a damn because the accumulated oil was too
thick from being distilled by engine heat and nobody else ever tried
it.

If you have a lot of oil accumulating in the crankcase, about all you
can do is remove the spark plug and kick the engine over until it blows
out the spark plug hole.

Or remove the cylinder head and kick the engine over and keep wiping up
the excess pre-mix as it blow out the transfer ports in the cylinder.

I forgot to shut the petcock off when I parked my Yamaha motocrosser,
and the crankcase was absolutely flooded with pre-mix. I would kick
start the engine and it would immediately foul the plug, and I would
clean the plug and start the engine and it would foul again.

I knew I had an accumulation of gasoline in the cylinder, but how to
get it out?

I removed the cylinder head and kicked and kicked and the pre-mix just
kept spraying out of the transfer ports and I wiped it up with a rag...

 

re: the oil injector system ? do i need to plug the feed line or dose
it matter ?

 

also dose it matter if the oil injector line is pluged or ?

 

It's a positive displacement pump, so whatever it pumps has to go out
the tube to the
engine. If you plug the output tube, you might ruin the pump because
the pressure has nowhere to go.

If you decide that you just won't feed it any oil to pump, it might
wear out inside because it probably needs the oil it's supposed to pump
to lubricate some of the internal parts.

Therefore, if you're not going to inject oil, the best bet is to remove
the injector pump and
cover the hole it came out of.

 

well Gene: in re: to you question i found in older bikes the injuctor
system can fail ! and then i would have only more problums ! 77 kawaski
w/injector system bypassed just fine! any other useful info greatly
appreciated !