YS four-strokes general information
Basic aticles by Rick Mattie
1. Recommended fuel |
a)
|
15 to 20% nitro and 20% oil
by volume. |
b)
|
use 100% synthetic, but 18%
synthetic and 2% castor is also a good mix. |
c) |
YS 20/20 Power master or
THE's 700R, FH-20,FH-25 |
2. Initial settings |
a) |
Low end needle 2.5 turns
out from full in (91 and SC only) |
b) |
Regulator flush |
c) |
High end needle 1.5 turns
out.
|
3. Fuel tank |
a) |
Watch for leaks, especially
ones that only appear under full pressure. This can cause surging. |
b) |
replacement every 150 flights.
|
4. |
Surging Could be worn out
piston. Piston life is about 200 flights.
|
5. |
Regulator tab goes forward.
|
6. |
Always replace all gaskets
upon re-assembly. Possible exception to this rule: valve cover.
|
7. |
Regulator edge may cut diaphragm.
Knock the edge off this or return Futaba in U.S.A
or Yamada in Japan.
|
8. |
Replace head gasket if burn
ring visible. Okay to keep if clean.
|
9. |
Cleaning. Use soap and water
or methanol. DO NOT USE GASOLINE! Ultrasonic cleaning recommended.
|
10. |
C-clips wear excessively
if not adjusted correctly. Replace every 150 flights. When adjusting
valves
it is best to adjust on the tight side.
|
11. |
Never use petroleum-based
after-run oil. Klotz okay. |
12. |
Plugs. Use OS F only. |
YS 91
|
1. Initial settings |
a) |
Low end needle 2.5 turns out from
full in |
b) |
Regulator flush |
c) |
High end needle 1.5 turns out.
Note that this engine richen slightly after it warms up. Do not
re- peak
when this happens as it will
begin to lean as it heats further.
|
2.Recommended RPM : 9200 max.
|
3.Loss of power when heats up : may be loose liner-
send back to Yamada in Japan or Futaba in U.S.A..
|
4.Can't shut off or can't set top end needle |
a) |
Look for vacuum leak in valve cover. Could be gasket or
ground off head.
|
5.Loss of power |
a) |
Ring |
b) |
Rear bearing : Should be replaced every 150 flights.
|
6.Recommended prop : 14x10 (13x11,13.5x10~13
propeller are not bad, too) |
---------------------------------------
New FZ 140L(Limited) engine ------------------------------------
* The YS140 has no timing marks.
*
Note that the fuel injection system
only injects fuel at speeds exceeding 2000 RPM.
Below this, fuel is inducted
in the normal manner. This is valuable information for troubleshooting!
*
Small bubbles in the regulator line
are normal at idle and typically go away at higher throttle settings.
Bigger
bubbles are symptomatic of diaphragm or regulator gasket problems.
YS 140
|
1. |
Availability : due out at the end
of the year for about the same price as the SC. It is 10gm. lighter
than
the SC and shares many parts.
|
2. |
Prop. : try 16.5x13.5. Don't over-nitro!
|
Setting up a YS 140 |
1. |
Always set up the top end first
and see that it runs consistently there.
|
2. |
Go to a 2000 RPM idle. If the RPM
slowly goes down, then the low end needle is set rich.
|
3. |
Set the low end needle so that
there is about a two second delay in transition to full throttle
due to richness. Engine should not immediately bang
to top end.
|
4. |
Set the Regulator at 3000-4000
RPM. If speed slowly drops in this range
then the regulator is
rich and needs to be leaned.
|
Breaking in the YS 140 |
1. |
about 10 ounces of fuel through
the engine and then puts it into the plane. Use a prop that maybe
runs in
the 8200 to 8300 range.
|
2. |
Note that the low end needle is
an air bleed type and its action has limited after about 4 &
1/2 turns out.
|
3. |
Note that the rotor screw is a
backward thread. Upon reassembly, use a dab of green Locktite on
it.
It's okay to bottom this screw out.
|
4. |
YS claims that the rear nipple
in the 140 back plate is a bleed that helps keep the regulator open
longer
than the connection used in previous engines.
|
5. |
Conrods are not symmetrical. |
6. |
The hole for the crank pin has
a wider taper on the crankshaft side. |
|