G8MNY > TECHNI 04.10.21 09:00l 198 Lines 9945 Bytes #999 (0) @ WW
BID : 48608_GB7CIP
Subj: MEDUSA SIP2300 Generator Repairs
Sent: 211004/0653Z @:GB7CIP.#32.GBR.EURO #:48608 [Caterham Surrey GBR]
To : TECH@WW
By G8MNY (Updated Jul 21)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
My MEDUSA SIP2300 4 stroke petrol generator, had done many years service, but
recently packed up while /P.
It has a Honda style engine & is the same as the WOLF 2.3kW generator. But my
one has been modified to properly open the throttle without dropping revs to
give a full peak power of about 3kW.
▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▄ █ _.==───────────.._ █ Tube
█/~~~~~~Tank~~~~~~~\█ █/" Large 12L Tank "\█ Cage
█-------------------█ Fuel Tap █===========================█
█\_____________/~~~~█ & filter\█|"""""~~~~~~~~~~~~~~~"""""|█
█ Tap(0) │elec █ STOP█Ů  °OK │ on│ " AC " Ţ█ AC
█Choke // Sol\____█ SWITCH█ |_ °Oil│ ║ │ = = = = _| █ 2x13A
█┌────┐ /~~~~~\\. █Pull █│~~""---..........---""~~││█
█│In- │,' /~~~\//\\ █Start █│F │ENGINE | | ││█
█│Take││ │ ( ) │ │ █ █│A │ (=)oil ALT | ││█
█└────┘ \ \___/ / █ █│N │ _____│_│__|_____| ││█
█ ┌' ┌─────┐ `┐ █ █└──┴──▄┘ └▄┴───┴┘█
Symptoms were slightly louder noise from the intake & not much power. Manually
opening the throttle there was no real increase in revs, & lots of smoke, from
loads of oil up the engine breather!
Discussing these symptoms with other engine experts, I got all sorts of bad
diagnoses. Myself I thought it could be a broken ring or valve spring. So I
started at the cylinder head & took the rocker cover off, the fault was
obvious! The exhaust valve rocker was at an angle & only pressing on the
spring, not the valve! The cause turned out to be a badly worn through push rod
guide plate (thin soft sheet steel).
ROCKER .-. PUSH ROD GUIDE PLATE
/( )\ Valve
│ │ GOOD BAD
│ _ │ ┌───────────┐ ┌───────────┐
│/ \│Stud, │ 0 0 │ Stud Holes │ 0 0 │
│(0)│Adjuster │ _ _ │ │ _ _ │
│\_/│& locknut │ ( ) ( ) │ ball end hole │ ( ) ( ) │
│ │ │ ŮoŢ ŮoŢ │ Guide Flanges │<o Ţ ŮoŢ │
\( )/ Pushrod │ │_│ │_│ │ │ │_│ │_│ │
~-~(domed end) └────^──────┘ o=Push rods └────^──────┘
As there was no wear seen on the push rod, the repair was just to remove the
adjusters & rockers, & then 2 studs to extract the plate. Then silver solder in
a bass guide bush, drilled out to the push rod size & then filled to make a "U"
channel, that should last much longer than a new tin can plate. The push rods
are also very rough (like needle files) & needed smoothing to a shine with fine
However things are never that simple, & putting back the 6m stud, I managed to
strip the thread in the soft aluminium cylinder head casting! :-( This was not
all my fault, as the stud hole was much shallower on the exhaust port than the
intake, despite the studs being the same length!
VALVE & SPRING
──//─────//─│┘ │ \
│// │// ││ │ \
STUD │ ,-│ ┌┐
_____│┌┐_____________ │/ │ /~~~ │ ┌─┐Lock
│_____││ _____________│ │ │ │ │ │ │Nut
M6 │└┘ Fine thread │\ │ \___.│ └─┘
│ HEX │ '-│ └┘
CAMPsh Rod │ │ / Adjuster
& ()============│======() )/
Follower │ └┘
I think not cleaning the hole out with a bottoming 6M tap, meant the shallower
stud hole filled up with old stud glue (lock tight) stopping the stud from
going home, & caused me to strip the casting. After many attempts to the get
the stud to grip well enough, I gave up, & drilled & tapped it out to M8, &
made an M6-M8 adapter sleeve from some steel roding. This worked fine.
ALTERNATOR FAN INSPECTION
On taking the silencer off for repainting, through the air duct I noticed the
black plastic alternator fan was well out of true, & was just at the point of
rubbing the casing. I had seen a failed generator where plastic bits were
coming out of an air vent & the rotor had all shorted out (over heated no fan?)
As my fan is right in the middle of the generator, I needed to split most of
the alternator from the engine, something I had not done before on this one, &
I had some trouble doing it to get at the fan.
End Fan │ │
Casting Casting│ │┌─────┐
┌─┬───┐____________┌────┬┘ └┤ ├─ Pull
│ │ │ │ ┌──┤ ENGINE │ │ \Start
End │ │ [││============│││ │ │ FAN │ \
Cover│ │ │ │ │ D│ CRANK │ │ │
│ │ │ ALTERNATOR │ │ U│ │ & │ │ < Engine
Alternator>│ │ │ STATOR │ │ C│ CASE │ │ │ < Cooling
Cooling >│ │ │ │ │ T│ │ FLY │ │ < Air
Air >│ │ [││============│││ │ │ │ /
│ │ │____________│ └──┤ │WHEEL│ /
└─┴┬─┬┘ └────┴────┬─┬─┤ ├─
└─┘ /|\ └─┘ └─────┘
Rubber SPLIT Rubber
Mounting IT HERE Mounting
The end cover lets you remove the electrical connections. Then extract the 4
outer long bolts clamping the stator. Remove the end casting (soft hammer may
be needed to free up the end bearing). Then remove the stator. This reveals
the diode pulsed excited rotor & fan, which is held to the engine crankshaft by
a long bolt down the middle of the rotor shaft. Pulling force is needed to
dislodge the close conical fit to the engine shaft. The fan casting I left on
flange ▒▒Ţ ▒▒Ţ
┌───────┐ \ Ů screws Ţ
Long ┌┐ / \ ┘Ţ' __ ┘ŢŢ' Large
BoltŮ===││▓ ROTOR ▓▓▓Ţ =:__ ▓▓▓Ţ repair
└┘ \ / ┐Ţ. Coned ┐ŢŢ. washer
Bearing└───────┘ Ů Engine Ţ
▒▒Ţ Shaft ▒▒Ţ
BAD FAN DISK
The fan disk is held on to the flange with 2 screws. I found there was no tube
spacer/Colette fitted on one of them & the plastic fan had been crushed &
slightly split due to this higher pressure. To solve this I made a large washer
from 3mm thick aluminium, so the weak plastic fan disk is better supported &
Eventually after 2 years none use the fan split, repair to was put a full size
ally disk in instead of the washer & rivit the 2 halves of the fan on to it.
On reassembly light oil (WD40) was sprayed all over the rotor & stator steel
laminations to halt bare steel rusting & maintain good electrical insulation
(water repellent) of the windings.
1/ Rusted petrol tank (from water in the /P fuel), which eventually holed the
tank. I used a phosphoric anti rust paint after 1st doing a test on the
petrol cap, that proved petrol had no effect on it. Then after a good clean
out & drying, I painted as much of the inside as I could. The pin hole had
raised the plastic dipped outer coating. So I scrapped that away & put a
plug of really thick Hammerite paint in the hole, & left it a few days to
dry & harden. I then redid the anti rust coat inside, & all is now well.
2/ Blocked fuel tap, This another consequence of water in the fuel, as the rust
particles build up, NOT in the fuel filter trap under the tap, but in the
cast pipe feeding the tap! Here I found hand held drills are the best used
to clean the pipe.
Tank ││l││ To remove the tap, you
Pipe ││o││ Rubber must have less than
~~~~~~~~┌─┤│c│├─┐~seals half a tank of fuel!
└─┤│k│├─┘ / screws
NUT ││e│└───┐===Ţ) Then remove the 2
││d│ │┌─┐Ţ CIRCULAR CLAMP tank bolts, turn
││ └────┘└┐├──. the tap to off & remove
│└──────┐ ││ \ rotating the rubber carb pipe.
Fuel │ ┌───┘ ││ \fuel path
to ─────┴─┐ │┌──┐┌┘├──┐ \ TAP Now remove & tilt the
carb ─────┬┐│ ││ │└─┘Ţ │ \ tank so the tap is clear
├┘└─┤├──┤===Ţ) \__/ of the starter case.
mesh filter│~~~ ~~│
Ţdirt Ů Losen the locking nut &
Ţ& H20Ů unscrew the tap, keeping
Ţbowl Ů the tank tilted & fuel at
▀▀███▀▀ the far end of the tank.
3/ Ignition Coil protection, this is also a bare steel construction & mounted
under the engine fan cover. To give another layer of damp protection I gave
this a coat of paint.
SIMULAR 23008 Genny Fault
Mike G4FVG reports an "Open Circuit" excitation capacitor (large AC cap), after
trying to run a fridge. (This might have been a Power factor problem, or Pump
stalled in compression stroke, <on mains a 5 min current timeout trip occurs>)
Any feedback on the working with it would be appreciated.
See my tech buls "MEDUSA SIP2300 Generator Info" & "Petrol Generators for /P
Y Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
Read previous mail | Read next mail