1981 Honda GL500 SilverWing

Today I set out to figure out why the temperature gauge wasn’t working.  I didn’t dare run the bike very far on the chance it might overheat.

In the end I think every electrical connection in the temperature gauge system was poor.  At first it looked like the sensor was bad (bad ground), then it looked like the 7V regulator wasn’t working.

Since I needed to debug the system anyway — literally –I pulled the tach off the bike so I could split the case.  Here’s the before with all of the dead spiders and the missing screw…

… and here’s the after.  The missing screw was rattling around inside.

I tested the temperature gauge on the bench using an adjustable power supply.  It worked just fine.  Then, it seemed like the 7V regulator wasn’t working,  I couldn’t measure 7V anywhere. I pulled it out and bench tested it as well.  It worked, but only when there was a load.   I used a small 12V box fan as a load and measure 6.95V.   Finally, after cleaning connections and putting everything back together, the entire temperature gauge system worked.

I’m still a bit suspicious of the sender unit.  It has a cold resistance of  7 kohm.  That’s higher than what you can find documented on the web.  Still, after starting the bike and letting it warm up, the temp gauge rose to the top of the narrow bar and stayed there.  So it seems to be working correctly, and it’s likely the thermostat opened up as well.

Time to get this bike running.

I started by checking for spark.  There was spark, but it didn’t look too energetic.   I cleaned the corroded coil grounds and hoped that would improve things a bit.  It might have, but the bike still wouldn’t start.

I was going to perform a compression test, but this bike has 12mm plugs and the smallest my tester goes is 14mm.  Oh, well.

I then checked for fuel flow out of the tank.  With all of the rust perhaps the filter was clogged.  No dice.  There was fuel flow, so that’s not the problem.

I then moved on to the carbs.  I didn’t have the parts to do carb rebuilds, so I pulled them off the bike, removed the bowls cleaned them up as best I could, and then reassembled.   I didn’t take pictures, but carbs were cleaner than expected inside.  Still, there were some clogged jets. After reinstalling the carbs the bike sprung to life with just a touch of the starter button.  Yes!

The brake lights wouldn’t work with either front, or rear brakes applied.  The front brake was a loose connection at the switch.  The problem with the rear brake was that the pedal adjustment was so tight that the pedal wouldn’t move far enough to pull on the switch.  I’ll know as soon as I pull the rear wheel, but the adjustment is now at the end of the rod suggesting new brake shoes in back.

The coolant overflow tank was empty, but the radiator was full, so I added a bit of distilled water for now.  I’m going to flush the cooling system in the near future.

Before working on the bike any more I wanted to give it a good washing.  It cleaned up better than I had hoped!  I took the second seat off and installed the small trunk.  Looks pretty good!!

Before wash

After wash.  A lot of what looked like surface corrosion was just dirt.

Taking a chance, I took the bike for a run around the block.  Everything seemed to be working OK except for the temperature gauge.  The really good news is that the odometer works, so perhaps this bike does only have 28k miles on it.  As the previous owner had donated the bike, I never spoke with him directly.  I hope to.  The seller was going to contact the PO to see if we could set something up.

 

 

I didn’t really have much time to look at the bike ‘proper’ before I bought it and brought it home.   What did I buy!?  Here’s a first look.

The seller made no claims about the mileage, which you can see here is around 28k.  Since the bike won’t start, there’s no simple way to check if the gauges and odometers function.

The bike came with an owners manual with previous-owner scribbles inside.  Assuming that the manual has always been with this bike, then the bike had 16,650 miles on it in 1987 and 22,222 miles in 2001.  Is it possible that the bike has been ridden less than 6000 miles in the last 15 years?  I think so.  One clue is the tires.  They look new, but are in fact 11 years old.  The seat has been recovered, but other things like the foot pegs and kickstand rubber aren’t very worn, nor are the handgrips.   We’ll just have to see if the odometer works.

If you look at the tach you’ll see webs and a bunch of dead baby spiders.  One of the faceplate screws has also come loose.

The bike still has the factory toolkit.  Cool!

The K&N label doesn’t lie.  There’s a serviceable K&N filter inside the airbox.

This is the worst thing on the bike, at least cosmetically.  See the rust on top of the tank?  There’s rust, varnish, or perhaps old sealant inside the tank as well.

The bike is very dirty.  I’ll let the rest of the pictures speak for themselves.