The real trick to getting ANY YS
engine to run properly is to use high-grade fuel, and tune it accordingly. Most people
have a nasty habit of turning screws they shouldn't be messing with, thus chasing the
tune. Also, most self-proclaimed engine jockies do not thoroughly understand the
YS induction principal. More often than not, they get the engine so out-of-whack they give
up on YS all together. YS tuning requires MORE brains, and LESS wrenching. Sometimes
I'm glad to see YS engines get an ignorant workover. This makes for a cheap source of
engines for me! I've purchased many de-tuned YS engines and had no problem getting them to
run like a bat out of hell, after un-doing someone elses mess.
PowerMaster YS 20/20 fuel is good, personally I prefer Cool Power 25%
nitro. It provides an excellent idle, and awesome top-end. You should never use old fuel,
and always use a filter during fueling. The real secret to keeping your YS in tip-top
shape is to completly purge the fuel system and close the carb (in kill-mode) when you're
done flying for the day. This eliminates getting humidity (moisture) in the crankcase,
thus your bearings and steel parts won't rust or corrode. This also purges the regulator
minimizing the chance of it sticking. I have occasionally used (YS safe) after-run oil
when I know I won't be flying for an extend time. Simply put the after-run oil directly in
the carb inlet, and flip the engine over to circulate the oil. But purging and closing the
carb completly does a great job too.
Tuning any YS engine can be potentially tricky if you don't know what
you're doing, especially if someone else has already messed with it. Sometimes you are
better off to reset the entire engine back to factory settings and start from ground zero.
If there's a fuel leak, crankcase pressure leak, or a check valve leak... it will
never tune properly. If the intake/exhaust valves are too loose or too tight, it will not
stay in tune properly. If you use old or dirty fuel, it will not tune properly. If the
regulator hold down screws (the 2 screws holding the regulator on the engine) are too
tight or loose, it wil not tune properly. I occasionally check all the screws in the
engine, and have found a loose one now and then.
- - - The initial TUNE UP - - -
You need to let the engine warm up and build up tank pressure before any
tuning takes place. Always attempt to tune the top-end first, making it slightly
rich, around 2 or 3 hundred RPM below peak. (If your top-end needle won't
adjust to a slightly rich setting, you may need to open the regulator a 32nd of a turn or
one screwdriver blade width). Gradually pull down to idle. If your
engine gets too rich while slowing down the engine, turn the regulator in about a quarter
turn. The idle must be at 2000 RPM. And no more than 2000 RPM, period. The YS low-end
needle is an air-bleed and works the OPPOSITE to what you
are accustomed to. Counter-clockwise LEANS and Clockwise
RICHENS. Also, the throttle barrel must be almost completly closed.
This draws fuel just like a "conventional" carb and cuts off the fuel injection,
which allows the lowend needle to work properly. If the throttle barrel is too open, the
lowend needle has no effect what so ever. While idling, you should be able to (transition)
throttle up to full throttle with no hesitation. If you encounter blubbering, or excessive
smoke (during transition only), you will need to lean the regulator
slightly (CLOCKWISE). If the engine stalls, stops smoking, or throws a prop,(during
transition only) richen the regulator (COUNTER
CLOCKWISE) slightly. The regulator doesn't need much adjustment to make a
big difference. You need to understand that the regulator transitions the engine and
provides the fuel supply regardless of speed. Do not adjust the regulator as you would a
top-end or low-end needle! It's adjusted for transition, period. Sinse the regulator does
supply fuel, it does affect the needle settings. But don't use the regulator to tune the
idle or top-end.
All fuel delivery above 2000 RPM is pressurized. IE:
FUEL INJECTION. If you try to set an idle with pressurized fuel, it will load up
and drip fuel making an erratic sluggish idle. To correct this, simply rotate the idle
needle flush with the sleeve and close the throttle barrel until a good idle(2000
RPM or slightly less) is achieved. Then you can fine-tune the idle again with the needle.
One word of caution about lean runs. YS engines are super charged, making them
particularly sensitive to detonation if they go too lean. They can, and will throw a prop
even if it's double nutted. You can also ruin your engine if it persists.
The mechanical condition of YS engines is critical for good reliable
performance. Any number of things can cause erratic running, including but not limited to;
valve adjustment, leaks, worn piston ring, worn valve guides, stretched diaphram, etc...
Also, the fuel delivery system must be very clean. Fuel filters are a must. The one-way
valve (check valve) must work properly and be turned the proper direction! The fuel tank
must be capable of withstanding up to 9 pounds of pressure continously.
Also, get in the habit of relieving the tank pressure after each flight! Pressure
regulators will occasionally leak when the engine isn't running (depending on the
crankshaft position and regulator setting) and will drip fuel.
All four stroke engines need an occasional valve adjustment, but in YS
engines it's very important. Check the clearance every 15 to 25 flights to be sure
it's within specifiaction. Do not over tighten the jam nuts on the rockers! They can, and
will break. Make sure the valve cover gasket seals properly. Do not put the valve cover on
backwards, and not attempt to run your engine without the valve cover on, period.
If you happen to notice air bubbles in your fuel line going from the
regulator to the carb, don't get your panties in a wad. This is perfectly normal! YS got
smart and started using dark blue fuel line here to minimize the fuel visibility. Don't
even think about trying to eliminate the bubbles. Your engine will be so out-of-whack it
won't even be funny.
I've never had to replace a glow plug in any YS engine, EVER. But if you
need to, use an OS Type F or and OEM YS plug. Don't try to save a buck or two buying cheap
glow plugs, you will regret it...
If your YS
engine is new it will likely be a little erratic at mid-throttle
until the ring seats. I do not recommend attempting to fine tune it until it is completly
broken in. Just keep it running on the rich side. Once broken in, it will settle down to a
good tune and stay tuned indefinitely. I prefer not to bench-run YS
engines! They don't get adequate cooling and they never un-load properly. I've found that
they break-in faster and run much better in actual flight. Last but not least, don't
change fuels if at all possible.
NOTE the opposite directions in RICH/LEAN settings in the
highspeed and lowspeed needles.
If you notice your idle screw doesn't have much, or any effect, you need
to close the throttle barrel more to make the air-bleed function and cut off the FUEL
INJECTION!
_ _ _ _ _ _
_
LISTEN, LOOK, THINK
These are my rules for working on any YS engine. Listen
to it, Look at it, and
Think about it. Do not arbitrarily
adjust anything! Listen to the engine, it's telling you something! Do you
hear unusual noises? IE: valves, rockers, bearings, clatter, etc... There could be a
mechanical problem... Look it over carefully.... Inspect valve clearances, Look for lost
or loose screws, Look for leaks, Look for anything un-usual.
(1) Think about what it's doing,
(2) think about what it should do,
(3) and think about what it takes to make it
happen.
All too often some well meaning, self-proclaimed
screwdriver jockey wants to mess with your engine. Bad
idea... If they don't have specific YS experience and a full understanding
of YS technology, I'd suggest they practice on someone
elses engine.
_ _ _ _ _ _ _ _
THE PERFECT running YS ENGINE
Start the engine in idle position. Let it warm up, and build up tank
pressure. Throttle it (slowly) up once to clear the crankcase, and finilize tank pressure.
Bring it back down to idle at 2000 RPM, it should be idling steady with slight
smoking. As you throttle up again (a little faster) you should see more smoke as the RPM
increases. It shouldn't bog, but smoking nicely If it bogs and there's a LACK of smoke,
the regulator is LEAN. If it bogs with lots of smoke, the regulator is RICH.. --CAUTION: make very small adjustments.-- As you speed up more, you
will see a more smoke all the way up to full throttle. At full throttle you should observe
a little less smoke than the transition. If there is the same amount of smoke, or more
smoke at full throttle it's a little too rich on the top-end needle. If
the smoke substantially disappears, and/or it bogs slightly, it's too lean on the top-end
needle. There is an interaction between the regulator and
the top-end needle since the regulator supplies the fuel. Do not
adjust the top-end with the regulator.
Understanding exactly how YS engine
components function, and how they interact is your BEST TOOL.
- - - - - - - - -
-
YS Technology
All YS four strokes are
founded on ( YS developed) crankcase super charging and fuel
injection technology. I'll attempt to explain how all of this works in
plain english...
All four stroke engines rotate two full revolutions
to make up the four strokes. IE: INTAKE stroke= 180 degrees, then the COMPRESSION
stroke=180 degrees, the POWER stroke=180 degrees, and finally the EXHAUST stroke=180
degrees, hence TWO revolutions of the crankshaft. This means that the piston travels up
twice, and down twice to complete the four cycles of which only 25% (power stroke) of the
cycles produce power. The remaining 75% consumes power. Also in a
conventional four stroke, all the work is performed on the TOP SIDE of the piston. In YS
engines, both the top and bottom of the piston have a job to do. YS technology utilizes
2/3rds of the 75% of the power robbing cycles to boost the intake cycle (IE:super
charge). This is done by taking advantage of the bottom side of the piston's up & down
motion. On the up strokes, the piston draws in air into the crankcase, however not the
fuel! On the down strokes of the piston, it "pushes" the charge
through the second half of the carb where it is injected with fuel then pressurized
into the airchamber. The YS engine gets TWO charges of pressure into the airchamber before
the intake valve opens up. The timing of the inlet to the crankcase and the outlet
to the airchamber is controlled by a rotary valve on the back of the crankshaft. While all
of this crankcase charging is being pushed into the airchamber, there's a small hole in
the front section of the crankshaft that is timed to send a pressure signal to the fuel
regulator. This signal opens the plunger and injects fuel in the second half of the carb
(the half that goes to the airchamber). This pressure signal also provides the needed fuel
tank pressure through the one-way valve. Fuel injection is a necessity, as there is
lots of air pressure on the airchamber side of the carb! Here is what all this
means; Instead of having the piston on intake stroke "suck" the mixture into the
cylinder like a conventional four stroke, it's now "pushed"or super charged into
the cylinder by the airchamber. This takes a lot less energy which translates to more of
the horsepower going to the propeller (in simple terms). Also, the cylinder is
"packed" with more air/fuel mixture increasing the "effective"
compression. Once again, consuming less power and actually generating more
horsepower.
Now let's take this a step further... In a
conventional four stroke, as the piston moves up & down it creates both a vacuum
(going up) and pressure (going down) in the crankcase. This consumes horsepower by
passing air back & forth through the crankcase vent. On a YS engine, the
"wouldbe" vacuum portion of the piston stroke is "equalized" via: the
first half of the carb (inlet) . IE" less power consumed. The
"wouldbe"pressure portion of the piston stroke is "equalized" via: the
second half of the carb going to the airchamber. Both of these functions are synchronized
and managed by the rotary valve. Hence, once again more power available to the prop. This
is why it's so critical that all YS four strokes be completly sealed. Meaning absolutely
no leaks, period! The entire function depends on the balance of perssures generated in the
crankcase. Not only does this balance provide the super charge to the cylinder, but
it also times the fuel injection and pressurize the fuel tank as well. For all of
this action to function as designed it's important the the YS engine be in perfect
mechanical condition!
This is an over-simplistic explaination, however it
gives you an idea of the extreme engineering and mechanical functions that YS designed
into their four strokes. There's no doubt that you get the most "bang for the
buck" with YS engines when you consider the engineering, machining, and technology
invested in every engine.
- - - -
- - - - - -
- - -
In my humble opinion... YS Engines are absolutely Fantastic, however
I do not recommend them for
novices, occasional sport fliers, and especially anyone mechanically inept . They're
the one's I end up buying engines from.... |
