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G8MNY  > TECH     16.06.18 10:00l 193 Lines 9789 Bytes #8 (0) @ WW
BID : 25445_GB7CIP
Subj: MEDUSA SIP2300 Generator Repairs
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 180616/0748Z @:GB7CIP.#32.GBR.EURO #:25445 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                    (Updated Jul 16)
(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.

                                        Gauge   Filler
                   _.==.._   Tube
/~~~~~~Tank~~~~~~~\               /"     Large 12L Tank    "\ Cage
-------------------      Fuel Tap ===========================
\_____________/~~~~      & filter\|"""""~~~~~~~~~~~~~~~"""""|
    Tap(0)   elec            STOP [] OK  on  " AC "      AC
Choke //   Sol\____         SWITCH |_  Oil   = =  = = _|  2x13A
Ŀ  /~~~~~\\.  Pull           ۳~~""---..........---""~~
۳In- ,' /~~~\//\\ Start          ۳F ENGINE      |     |  
۳Take  ( )                   ۳A        (=)oil ALT |  
 \ \___/  /                 ۳N   ________|_____|  
     ' Ŀ `                           
"""""""""""""""""""                

THE FAULT
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
        _                    Ŀ               Ŀ
       / \Stud,                0     0     Stud Holes    0     0  
       (0)Adjuster             _     _                   _     _  
       \_/& locknut           ( )   ( )  ball end hole  ( )   ( ) 
                              o   o  Guide Flanges <o    o 
       \( )/ 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
emery cloth.

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
              //    /
          ////             .ROCKER
          ////ij              \
          //    //                 \
                                        
                       STUD           ,-        ڿ
            _____ڿ_____________    /      /~~~  ĿLock
           _____ _____________                Nut
            M6      Fine thread   \      \___. 
                  HEX                '-        
CAM     Push Rod                      /    Adjuster
 & ()==================()            )/
Follower                            
            Rod Guide
              plate

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.

                                      HEAD
              End              Fan        
            Casting          Casting      Ŀ
           Ŀ____________            Pull
                            Ĵ ENGINE       \Start
       End   [============           FAN   \
      Cover                  D CRANK         
                ALTERNATOR   U          &     < Engine
Alternator>       STATOR     C  CASE          < Cooling
  Cooling >                  T         FLY    < Air
    Air   >  [============                 /
               ____________ Ĵ        WHEEL /
                       Ĵ     
                          /|\         
             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
the engine.

                 flange                            
            Ŀ  \  screws                       
Long    ڿ /         \  '      __                    ' Large
Bolt===   ROTOR        =:__                     repair
         \         /  .      Coned                 . washer
     Bearing           Engine                 
                              Shaft                
                  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 &
kept straighter.

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.

PREVIOUS PROBLEMS
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.

  Threaded ڿbڿ
    Tank   l                             To remove the tap, you
    Pipe   o   Rubber                    must have less than
 ~~~~~~~~ĴcĿ~seals                     half a tank of fuel!
         Ĵk  /    screws
      NUT  eĿ===)                    Then remove the 2
           d    Ŀ   CIRCULAR CLAMP    tank bolts, turn
            .                   the tap to off & remove
           Ŀ    \ rotating         the rubber carb pipe.
Fuel               \fuel path
to    Ŀ ĿĿ  \ TAP            Now remove & tilt the
carb  ¿       \               tank so the tap is clear
           ĴĴ===) \__/               of the starter case.
mesh filter~~~  ~~
            dirt                           Losen the locking nut &
            & H20                          unscrew the tap, keeping
            bowl                           the tank tilted & fuel at
                                      the far end of the tank.
              NUT

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
SSB"


Y Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP


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