Moto Guzzi Robin

Pictures and tecs by John Wengren

ROBIN Moped details:

        Engine                    1-cylinder, 2 stroke
        Bore                       40 mm
        Stroke                    39mm
        Displacement          49 cc
        Horse Power           1.5 HP at 4400rpm
        Compression ratio  8.5 to 1

        Fuel                        4 per cent oil/patrol mixture
        Ignition                   Magneto-flywheel, alternator
        Cooling                  Air Cooled
        Clutch                    Centrifugal, automatic
        Gearbox                 Single Speed
        Starting                   Pedal Kick
        Primay drive            By Gears
        Secondary drive      By pedals

Questions from the owner:

I would like to ask if you could help me with the following problem, or point me in the direction of who to ask...

At the moment, the moped is not running correctly, and I'm writing to ask if you would please suggest any fixes for the following, or if you know of any experts with mopeds. In America, in my state of
Pennsylvania, there are few, if any people who are knowledgeable on this.
I've been having consistent problems with the motor cutting out, and stopping, once it kicks itself out of Choke mode.  There have been less occasions, (less than 10 percent of rides)  where the motor has kept going after kicking out of choke mode.  It ran fine before this occurred, and it seemed to come on during some of the hotter summer heat we've been experiencing.

I've done the following to try to diagnose the problem...
I've cleaned the sparkplug, and the fuel filter. I cleaned the air filter too. The fuel mix does come thru the hose to the carb, and there is no filter in, or at the tank that I can tell. I've taken the muffler off, and looked only to see a clean exhaust, with no back end blockages, nor any dirt at all.  After the problem started, I also removed the old oil and replaced it with  5.5 oz. of new oil. I watched the sliding door to the carb rise up as I turned the accelerator handle to make sure that this was allowing for more gas as the handle was turned. The door reacted with the turn.
Still it is consistent with running while choked, then coughing and sputtering until stopping after the chokes kicks off.  I've taken the RPM screw from one end of the spectrum to the other while idling with the choke on, and stopped at the point where it barely grabs and leaves idling.  It seems like it could keep going and going  if the choke was left on. All bolts were tightened and retightened, to try to leave no extra air into the system.
Can you suggest anything  for me to try on this old, but still very worthwhile moped? (or anybody to eMail to?)
Do you think that it may need some adjustment to the carburetor? What is the adjustment for this, if there is any? The name and numbers on the carb. are Dell'Orto
SHA 14 9

These appear directly below the RPM screw adjustment.

I appreciate any help you can offer.

Sincerely,

John Wengren
303 North St
Catawissa, PA  17820  USA