Squirrel Power: Saving a Suzuki FA50

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Pulling the oil tank is easy, but make sure you drain all the oil out first or it will make a hellacious mess (just yank the feed line to the oil pump and let gravity do the rest).  You can see the level of old oil that was in the tank from where it has stained the plastic.  You can also see all the farmyard crud from sitting in a barn for over a decade.  All of this was cleaned off.

With all the old fluids drained, we carefully pulled the carb and yanked the bowl.  The bowl had some varnish and evidence of old oil, so we cleaned out as much of the staining as we could.  The float moved freely, which was great news. Oil sludge can sometimes clog the float pivot and make the float stick, potentially flooding the carb and causing a fire!  We also pulled each jet and cleaned them with carb spray and a couple strands from a scrap of wire.  The jets are tiny and the oil muck doesn’t always come out with spray alone.  We also cleaned the carb body before bolting it all back together.

 

The floats were gross, but moved freely.  Above them, lots of varnish and corrosion from old fuel remained.  
The bowl was varnished and a bit oily, but nothing too severe.  At first we tried some carb cleaner and scrubbing, but the goo was pretty well stuck in there.  This would take more drastic measures to fix…

If you’ve never played with a carb before, these are the jets.  They are tiny, so don’t drop them!  The longer one is the idle jet (which fuels the engine at low RPMs), and the shorter, fatter one is the main jet (adding fuel at higher RPMs).  Lots of FA50s that have sat for a long time suffer from poor idling, most often attributed to a clogged idle jet.  Given its size, you can see why this is so often the case.  Between old oil and aluminum oxide corrosion caused by ethanol fuels, cleaning carburetors should be part of the annual maintenance ritual for any old moped owner.
The Mikuni carb uses a slide throttle instead of the more common butterfly.  An important tip when reinstalling the carb is to smear a bit of oil on the barrel and its cylinder.  The engine oil doesn’t really get up here and if these parts are not properly lubricated, the throttle will stick.  

With the fuel and oil systems taken care of, we moved to the electrics.  We pulled the spark plug and grounded it to check for spark and found none.  The first thing we tried was replacing the spark plug as the original one was very old and caked with crud.  This did nothing, so we pulled out the multimeter and began hunting lost electrons.  The nice thing about a bike this simple and old is that all the electrics can be checked with a standard multimeter (also there’s about 8 wires in the entire wiring harness).  We started at the ignition switch and found it worked perfectly.  Next, we moved to the ignition coil.  It too passed its checks.  We pulled the magneto cover and checked the wiring for continuity: the harness was perfect, as was the rectifier.  The only other culprit was the PEI unit, and those never fail, right?

 

The original NGK plug was pretty gross, so we swapped it for a new Autolite plug.  The NGK can be tough to find, but nearly every plug manufacturer makes an equivalent, so sourcing one at a parts store is easy.  Even with this new plug, we still weren't getting spark.
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