'59 QD 20 gastank filling with exhuast

I have a QD 20 I acquired to do a rehab on.

After a carb clean out and high pressure air blast through the jets, replacing the coils, replace recoil and water pump I tried a start-up.

It starts with some effort but runs reluctantly before gasping out. My guess is it is likely needing parts replaced in the carb or at least, more attention in that department.

What I am wondering is why, after only a few minutes of running, the water in the pail was black with oil (or carbon), the smoke was one puff away from signaling the fire dept. and most alarming, the gas tank was full of exhaust when I opened it.

I understand the engine produces the pressure that works as a fuel pump by pressurizing the gas tank but I can't understand why exhaust would be in there.

Is this not potentially One Backfire Away From Being A Bomb!

Any thought appreciated.

Cheers,
Kelly

Re: '59 QD 20 gastank filling with exhuast

QD-20 1959 10hp Johnson.

The source of pressurized air for a pressure tank is due to the force of the piston traveling downwards, forcing pressure into the crankcase which is released via a small rubber valve to a air hose leading to the fuel tank. There shouldn't be any exhaust fumes within that scenario.

If exhaust fumes are actually in that pressure tank, I can only think of two possible reasons..... one being that a piston has bad rings that are allowing the combustion to travel past the piston and into the crankcase area......

OR the points are set so far off that the initial combustion point is such that the fuel ignites before the intake port is fully closed. Actually I don't see how the engine could run if this was the case but as Forest Gump once said "it happens".

The oil in the barrel problem is common when using a 24/1 mixture or any heavier oil mixture.

Re: '59 QD 20 gastank filling with exhuast

I believe if you crack the cap just after running there will be visable haze in the tank.
In fact as I recall the sudden release of the pressure may result in a vapor in the air space of the tank.As mentioned running in a barrel is very smokey and the water will be gunky very quickly.Have you adjusted the high and low speed needle valves?

Re: '59 QD 20 gastank filling with exhuast

For sure there is a buildup of exhaust fumes in the gas tank. So first thing to do is disconnect the pressure line from the crankcase and raise the fuel tank above the motor for the time being.

The points were set Top center at .020 tight so hopefully I am close. Good consistent spark.

I adjusted the low speed while it ran for a while and it wasn't hugely influential but for sure this area needs more attention.

When I started the project I was getting about 75 psi compression in each cylinder - cold and with a pull start.

Hope there are some possible clues here.

BTW, my HD25 that runs 16:1 doesn't make this kind of smoke and oil slick

Re: '59 QD 20 gastank filling with exhuast

The top quality advanced 50/1 oil of today allows you to safely use a 24/1 mixture in that engine..... 1 quart of 50/1 oil to 6 gallons of gasoline.

(Point Setting Of Magneto Models)
(J. Reeves)

Set the points as follows. Have the flywheel key aligned with the fiber rubber portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

NOTE: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.

Re: '59 QD 20 gastank filling with exhuast

I run 24:1 in the QD20 as prescribed. I was thinking I may be able to get away with less oil myself, as you stated. Maybe a 32:1 mixture? Don't know.
Are you suggesting 24:1 on the HD25? ... anyway, I'm straying off topic.

I gaped the points as you indicate but did not wipe them with any solvent. Just sanded away any arc marks and blew off with pressurized air.

... but still, there's the exhaust in the crankcase. Hope this doesn't indicate I have a parts motor.

Re: '59 QD 20 gastank filling with exhuast

There is a check valve ,that is in the area of the reed valve assembly,that's supposed to prevent pressure in the tank from returning to the crankcase.
If that has failed perhaps it makes it appear like exhaust is in the crankcase.
Perhaps this is contributing to the extra smokeyness.
It seems unlikely that there is much if any blow by with 85psi compression.
I think if one piston was weak it would get worse as you continue to run it.
Have you tried a decarb treatment with something like seafoam I've seen
very good compression results here after a treatment.I think if you had a weak piston the treatment might make it show up as carbon was removed by the treatment.
I think there is also a crankcase drain that keeps excess fuel from accumulating in the crankcase.Could cause a smokey condition if plugged.?
I wouldn't run the HD25 at less than 16:1 unless someone at www.aomci.org suggested it.

Re: '59 QD 20 gastank filling with exhuast

Thanks @Steelespike

Seems like a very good lead. I will investigate all your suggestions.

Any idea if the cost of a fix for such a problem would be warranted in a motor that I have about $150 in already? Just parts as I would obviously be doing my own labour.

Haven't asked the boys on aomci. Still in the process of setting up a membership.

Cheers

Re: '59 QD 20 gastank filling with exhuast

I don't have a clue on the check valve cost.A well established Evinrude/Johnson dealer may be able to help.You may have to get a parts manual to get the part number.Its possible it may just need service.As far as the crankcase drain I think
its just a small 1/8 id metal tube leading toward the water could be plugged or maybe bent etc.