Motorcycle Repair: Honda spree - 1984

Question
I bought a 1984 Honda Moped Iowa Spree recently with it running by starting it with a drill motor and a 14 mm socket on the flywheel.  It runs fine and the motor can be started with a 14 volt dewalt drill on high speed RPM.  The engine seems to have and adequate amount of power and it will reach 25 MPH.  The previous owner supplied a start motor and bendix and said it needs replacing and all would be fine.  The starter supplied seemed to slow in RPM after about 10 second of free spinning so we disassembled the starter in the machine, cleaned it and reassembled – which it sounds strong and consistent.  The machine had no bendix in it, only the one supplied was present; so we assembled it into the case.  It looks to fit well into the case and engine and mesh with the starter.  Both ends /  bushing fit nicely into the engine and case.  The bendix shows no signs of looseness and the radial play is very small.  The gear moves in / out smoothly and will engage with the ring gear ok by hand when the case is off and only one end of the bendix is in the engine bushing.  The ring gear seams flat and all the teeth are ok.  There was no sighs of metal saving in the case housing the belt and clutch.  

With everything assembled – when cranking – a high pitch whining noise is coming from the starter area.  The RPM seems to be very slow and will almost stop about every ½ revolution.  Even with the spark plug removed, the same slow/fast Engine RPM is present.  The battery is brand new and fully charged.  All the wiring was checked and looks fine.  The same slow/fast RPM exist even when a battery pack is put directly on the starter – even without the spark plug.  There seems to be a binding with the ring and bendix, however everything looks ok.  I loosened the case bolts and moved it forward and back during cranking to attempt to give more ring gear clearance; however it didn’t help much and the whining noise did not change
What could be the cause of the slow and extremely variable RPM – and the whining noise, and what do we need to do to fix it?

Answer
Michael,  I can't say that I have been exposed to one of these little scooters, so working knowledge is just about zero. I did notice a gasket kit for one in my inventory, though, if you need one for the engine.

Quick research shows a part number change for the part:

31209-GK8-003 PINION ASSY., STARTER (65t)  vs. 31209-GK8-013 PINION ASSY., STARTER

I suspect that the starter pinion (Bendix) is failing internally and/or the original part has a design flaw requiring some in-house rework. You might want to try disassembling the drive unit and seeing if there are signs of distress inside, then plan on buying an updated part.

You might also check the starter motor armature for an open winding.

Bill Silver