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#Post#: 70429--------------------------------------------------
Gas Engine Setup And Running Recomedations
By: 660magnum Date: March 20, 2016, 10:17 am
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Av8tor1977 recently sent me a .pdf file as an aide for a
conversion engine he made up for a customer. I think it would be
a handy guide for the first time engine converter so I have
presented it here.
This was written for a 48cc Poulan engine for a Airboat, but the
technique is applicable to all two stroke engines. There are
several pictures and diagrams.
[CENTER]GAS ENGINE SET UP AND RUNNING RECOMMENDATIONS[/CENTER]
[B][CENTER](48cc Poulan engine for Airboat, but most are
applicable to all two stroke engines.)[/CENTER]
1. A 48cc engine will run approximately 10 minutes at full
throttle on a 16 oz. fuel tank. So when used at varying throttle
settings, a 16 oz to 24 oz tank will last quite a while in a
model and is sufficient. Get one at a hobby shop, and be sure to
get a [B][U]gasoline proof stopper[/U][/B] for the tank, and
some Tygon fuel line. Regular silicone fuel line such as used
for glow engines cannot be used with gasoline; it will dissolve
it. Discard the fuel line that comes with the new fuel tank, and
the stopper.
2. Get a felt type fuel filter pickup such as is used on
weedeaters, leaf blowers, chainsaws, etc. and use it inside the
fuel tank. Walmart, Home Depot, Lowes, Ace Hardware, etc.
usually have these, or any small engine repair shop.
3. I recommend a 3 line fuel system. (See attached drawing.)
Secure all fuel line fittings with either very small nylon
Tywraps, or safety wire wrapped double and twisted tight. You
should also use “fuel barbs” on each connection. (Available at
the hobby shop.) Another trick is to use 1/8” brass ferrules for
copper tube compression unions, soldered onto the brass tubes
coming from the fuel tank to help the fuel line seal and stay in
place. They are cheap and can be found at the hardware store.
Use ferrules or hose barbs on the connections inside the fuel
tank as well. [B][U]ANY[/U][/B] air/fuel leak at any of your
fuel line connections will cause the fuel pump to not pump fuel,
and make you crazy trying to figure out why the engine either
won’t run, or won’t run properly. Use a filter on your fueling
setup to filter the fuel as it goes into the tank. A dedicated
fuel can with another of the felt filters is a good setup.
[img]
(HTM) http://www.rcuniverse.com/forum/attachment.php?attachmentid=2153076&d=1458362755[/img]
4. Fuel tank location is not important as the carb has a built
in fuel pump.
5. Use premium fuel, and if possible, use fuel without ethanol
added. (Hard to find.)Store your unused fuel in a dark, cool,
and dry place. Leave about a half a tank of fuel in the tank of
the airboat when you are done playing, and cap off the vent line
from the tank. If you ran it out of gas on the last run, I would
start it again, rev it to full throttle, and choke the engine to
kill it. This provides extra lubrication in the engine for
storage, and also makes sure the carb is full of fuel for
storage which helps the diaphragms inside last longer. This
would be extra important in an airboat, as it is exposed to
water and the extra lubrication in the engine for storage is
important.
6. Use a high quality non-synthetic oil such as [B][U]“Pennzoil
for Air Cooled Engines”[/U][/B] at a mixing ratio of 32:1 for
the first two gallons of gasoline used in the engine. (A 32:1
ratio is 4 ounces of oil to a gallon of gas.) Do not use mixed
fuel that is more than 2 weeks old. Do not use a “multi-purpose”
oil and do not use a “marine” two stroke oil. The correct
Pennzoil can be located from numerous sources on the internet.
After the first two gallons, you can switch to a 40:1 ratio if
you like, and you can also switch to a good synthetic two stroke
oil like [B][U]“Stihl Ultra HP”[/U][/B] or [B][U]“Redline Racing
Oil”[/U][/B]. Use these at 40:1 ratio as well. Do not mix fuel
with different oils together as it can cause problems. You will
find many, many opinions on all this; but these have served me
and others well for many years, and no “blown” engines. You
can’t go wrong with what I have outlined.
7. Yours is a magneto ignition engine, and your kill switch
setup is very important. There is a spade terminal on the
magneto coil. You run a wire from this terminal to a good
quality switch, located well away from the propeller but in a
very easy to access spot.. From the other side of the switch,
run a wire to the engine and connect it firmly to any metal part
of the engine. Now this is important to remember; when the
switch is [B][U]“ON”[/U][/B], that [B][U]KILLS[/U][/B] the
engine. When that terminal on the coil is
[B][U]connected[/U][/B] to the engine, or grounded, it kills the
engine. So if your switch is labeled, you must remember to
reverse the label so that when the switch is turned in the
direction that allows electricity to flow, that is
[B][U]“OFF”[/U][/B] for the engine. You don’t want to confuse
this issue and either have an engine that won’t start because
you’ve labeled things wrong, or have an engine that is
[B][U]“HOT”[/U][/B], or ready to start when you think it is off.
[img]
(HTM) http://www.rcuniverse.com/forum/attachment.php?attachmentid=2153072&d=1458359026[/img]
8. Magneto engines can be difficult to hand start, so I
recommend coming up with an electric starter. A standard starter
and 12 volt battery for normal glow engine model airplane use
will not start a 48cc gas engine. Not enough power. The cheapest
and easiest way is to use a battery powered [B][U]18 volt
drill[/U][/B]. These can be bought at Harbor Freight Tools for
around 25 bucks. Then buy a starter cone, “Tower Hobbies”
[B][U]#LXL403[/U][/B], and the rubber insert for it,
[B][U]#LXL404.[/U][/B] Pick up a 3” long grade five 3/8” bolt,
two “star” washers, and a 3/8” nut. Drill out the center hole in
the starter cone to fit the 3/8” bolt. Insert the bolt into the
cone with a star lock washer on each side, and then tighten the
nut firmly. Install the rubber insert into the cone with the
cone side inward. (The cone side is used for propeller spinners
on airplanes.) You can then chuck the bolt/starter cone assembly
into the drill, and you have a great starter. This will cost far
less than any hobby starter and battery that you could buy that
will start this size engine, and you have a drill that you can
use for other things as well! The drill starter works very well,
better than most hobby starters in fact. Just remember that when
facing the propeller, your engine turns counter-clockwise, so
you have to run the drill in reverse to start your
engine.
[img]
(HTM) http://www.rcuniverse.com/forum/attachment.php?attachmentid=2153073&d=1458361087[/img]
9. Your engine has been test run and the carburetor mixtures
set. However, you will need to fine tune it for your particular
fuel, oil, prop, atmospheric conditions, temperature, altitude,
etc. This is true of any engine a person buys; they must be fine
tuned by you, the user. To start the engine the first time or
any time it has been run out of fuel, choke the engine by hand.
It works best if you hold your finger or thumb over the carb
velocity stack, open the throttle fully, and flip the prop over
by hand until you see the fuel in the fuel line reach the carb.
[B][U]MAKE SURE THE MAGNETO SWITCH IS OFF[/U][/B] WHILE YOU DO
THIS, AND IT IS ALWAYS BEST TO [B][U]HAVE SOMEONE ASSIST
YOU[/U][/B] WHEN STARTING THE ENGINE! It might be even better to
remove the spark plug wire. (Remember, if you lose continuity in
your kill circuit on a magneto engine, the engine will start!)
Once the fuel reaches the carb, flip it with your finger still
over the velocity stack about three or four more times. This
should fill the carb with fuel. Then set the throttle at about
1/8 open, open the choke all the way, turn the mag switch
on, and use the electric starter to spin the engine over. If it
does not start within several seconds of cranking, stop and
close the choke. With the throttle still about 1/8 open and the
choke firmly closed, crank the engine again and listen for it to
briefly start and quit, or “pop”. (Listen for a sound from the
engine and/or smoke from the exhaust. Some engines will start
and run for a brief moment on the choke, others will only make a
“pop” or “burble” sound.) Then stop cranking and open the choke.
Now when you crank it over, it will start and keep running. If
it starts and runs for a bit and quits, you might need to do the
choke process once again. This will usually only occur if it is
cold out, or if your low speed needle is a touch lean. If you
are happy with how the engine has been running, I would leave
the low speed needle alone, and just accept that it sometimes
will need choked twice to keep running the first run of the day.
On subsequent starts on the same day, always try to start the
engine without the choke. If it won’t start, then go ahead and
choke it, crank it till it pops or runs a bit and stops, then
open the choke, start it again,
and you are “good to go”.
[img]
(HTM) http://www.rcuniverse.com/forum/attachment.php?attachmentid=2153074&d=1458361134[/img]
10. Let the engine warm up fully. This will take at least two
minutes, and maybe longer if it is cold out. After the first
minute or so, you can give it some short (3 second) full
throttle blasts to help it warm up. Once it is fully warmed up,
you can adjust the mixture needles. When doing so, always make
small adjustments, and give the engine some time to stabilize at
the new setting. The high speed needle is best adjusted with a
tachometer, but can be done by ear if you are careful. The high
speed needle has an “H” right next to it, and is the one I have
put a brass extension on for adjusting it by hand. It is really
tough to adjust the high speed needle with a screwdriver with
the engine screaming and vibrating away, and dangerous to do so
as well. Thus the hand adjuster I added to the high speed
needle. Set the engine at full throttle, and adjust that high
speed needle for maximum rpms, then open it,
(counter-clockwise), about 1/16 of a turn. To set the low speed
needle, which has an “L” right next to it, bring the engine down
to a low idle, and listen to it. If it idles dead smooth, it
might be a touch lean. Try quickly advancing the throttle. If
the engine immediately hesitates abruptly or dies, then the low
speed needle is
in fact lean. Adjust the needle 1/8 turn, (no more) open, and
try again. What you want to achieve is the leanest low speed
mixture you can that still provides good throttle response. If
when you listen to the engine at idle and it idles just a bit
rough or with an occasional burble, it might be at a good
setting. Let it idle like that for a bit, and see if it begins
to slow down and/or smoke more. If so, it is too rich at idle.
Another sign of a rich idle is a slow, smoky and burbling
acceleration, especially after the engine has idled for a bit.
In this case, lean the idle, (low mixture screw turned inwards),
a [B][U]little[/U][/B] at a time until you get that hesitation
on acceleration, then richen it until the hesitation goes away.
Once you’re done with the idle, you will need to re-check the
high speed mixture, as changes in the low speed mixture will
affect the high speed mixture. Be sure to re-check the high
speed setting before using the engine. Lean runs kill engines,
rich runs only kill mosquitoes. (Excess smoke.) Also note that
if you have been idling the engine rich for a bit, you will need
to do a full throttle blast to clear out the engine before you
can go back and set the idle mixture effectively. It pays to
take the time to adjust the engine properly, but the good news
is that once done, the settings won’t change unless you change
the propeller type or size, or the fuel or oil type or ratios.
It will hold the settings and you will not have to constantly
re-adjust as is common with glow engines.
[img]
(HTM) http://www.rcuniverse.com/forum/attachment.php?attachmentid=2153075&d=1458361721[/img]
That, along with the drawings I have provided, is about it. Keep
in mind that a model engine is different from an engine used in
a weedeater, leaf blower, chainsaw, etc. and this is because it
is always “loaded” (turning the prop), while other engines run
free until you actually put them to work. This is why the tuning
and starting procedures differ and are so important.
Enjoy your new engine. If you take care of it, it will outlast
[B][U]you![/U][/B]
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