My Harley Davidson Aermacchi Page

One of my few forays into 4 strokes

Warning: the pictures are links to the full size images...they are large files and will take a while ot load on dial-up.

For the first time in 12 years, I have a 4 stroke bike.  I ran into a deal that was too good to pass up on a pair of 1973 Harley Davidson Sprint SS350 motorcycles.  From what I have found out from my local HD dealers, these are among the bikes that Harley Davidson would like to forget that they made.  First off, they are from the AMF era and second, they are Italian made by Aermacchi.

These 2 bikes came to me as non runners.  One was complete, but had no compression and the other was a mostly complete parts bike.  The parts bike is missing the gas tank and the motor is siezed fast.  The complete bike was bought new at my local HD dealership in 1973 and the parts bike is of unknown origin, but it came from a local junkyard that is famous (at least locally) for being under water every time it rains.

So I drag the 2 bikes home on 7/26/06 and unload the bikes.  I basically ignore the parts bike, being that it is just that.  I have no service manual for this bike and all of my 4 stroke experience is from working as a mechanic through college, so whatever I do will be based on old experience.  I pull the head off of the complete bike and find that the exhaust valve is stuck open.  That explains the lack of compression.  So, I do what any reasonable mechanic would do.  I pull the valve retainers and try to remove the valve.  I get it part of the way out and I hear a thunk.  I found this. 

Exhaust Valve

That explains why the valve was stuck open.  At least it didn't hit the piston and pop a hole in it.  Well, I can't do much with the bike until I get back from Mid-Ohio Vintage Days, so I park the bike and take off for the weekend.  I come home and pull the head off of the parts bike and find what I expected.  A motor full of water and rust.  But the valves are salvageable, so I pull the exhaust valve out of it, clean up the valve and put it in the head I took off the original motor.  One thing that I want to mention.  The Aermacchi engineers need to be beaten severely.  There is almost no room to get to the head bolts on this bike.  I had to take a 17 mm box wrench and grind it to less than 1/2 it's thickness to get the head bolts off. and back on.  I change the oil (looks like a milkshake) and clean the filter and then I reassemble the motor and try to fire it off.  No dice.  It's not even trying to start.  Let me mention again that I have no service manual on this bike, so I have no idea what I'm looking for. 

I don't know if the bike is CDI, points, magneto, or what.  I was told that the bike was CDI, so I go to replace what I was told was the CDI box with the one from the parts bike.  The markings on the "CDI" box told me that it was the voltage regulator/rectifier.  So now I go looking for a set of points.  It's got to be under one of the covers, so I start opening stuff up, trying to be logical about it.  I find the points on the second attempt.  They are badly corroded, so I removed them, disassembled them and cleaned them up.  I put it all back together, guessing at the point gap, setting the points to about .018".  Now I'm getting good spark.  Fortunately the bike is electric start.  I hit the starter and the bike occasionally spits, but it won't start.  I pull the plug, spin the motor over to get it to TDC and I got spark at TDC.  No reason that the bike won't start unless it's not getting fuel.  The previous owner told me that he had cleaned the carb, so I didn't do that before I tried to start the bike.  I should know better.  I pull the carb and clean it.  IF he had cleaned the carb, he did it 3 or 4 years ago.  What a mess.  I put the carb back on...same results.  It won't start.  Now this motor is constructed in a wierd fashion.  It's sort of like a single cylinder air-cooled VW.  BUT the pushrods cross...they are horizontal in the block, but vertical in the head.  I thought mayby I got them backwards, so I pull the rocker covers to watch how the valves open in relation to spinning the motor over.  I got the pushrods in correctly.  Brain flash...pull the plug again and check to see WHEN the plug fires in relation to the valve action.  The spark plug fires just before the intake valve opened.  Bingo!!!  Motor is 180 degrees out of time.  Since the motor doesn't look like it's been disturbed, I take a chance that someone was messing with it in the past and I pull the points cam.  I rotate the cam 180 degrees and I'm pleasantly suprised that it locks back in place.  I hit the starter and the bike fires immediately and spews oil out of the rocker covers.  I'm a happy camper...the bike runs.

I have to hold the choke open with a pair of pliers, but it's running.  The choke lever is missing.  I've been patching things until I get everything functional or decide that the bike will cost more to fix than it's worth.  So the choke gets fixed with a piece of scrap aluminum that I had lying around.

Homemade choke lever

Next, I check the electrical system.  The bike's battery is dying after a couple of days.  The bike uses a standard garden tractor battery and I bought a 375 amp battery at Wal-mart for $20, so something is drawing a LOT of current when it's off.  I found a wiring diagram on the Internet, but it's next to useless.  I can barely read it.  Fortunately, I found a group on Yahoo that specializes in these bikes and one of the members there sent me a wiring diagram that I could read.  I check out my wiring and it's a mess.  Someone had played around and got a LOT of things hooked up incorrectly, mainly the nightmare of an ignition switch..  I rewired the bike correctly and all of a sudden, it's charging and the lights are working.  The turn signals are still not working, but it seems that the switch is bad.  I'm either going to have to repair the switch or find a good replacement.  Here is a pic of the back of the ignition switch.  You can see that it's pretty confusing.

Ignition switch...rear view

Since the bike came into my possesion minus the title, I had 2 options...use a title service to get a title OR call a friend of mine in a non-title state to get it registered and have him send me a bill of sale with a current registration.  I chose the second option.  The paperwork showed up 3 days ago, so now I just have to go to my local DMV and get it registered in my name.

Here is the bike as it is today, 8/19/06.  It's a runner and I've put a few miles on it.

Right Side

Left Side

Rear view

Front View

Anyway, the bike is rapidly approaching being road legal.  I need to get some tires for it.  You can almost see the air through the cracks in the sidewalls.  I'm going to have to figure out something for the turn signals so that the bike will pass PA state safety inspection...either that or register it as an antique.  Once I get things squared away with the bike, I'll do a full restore on it.  This is one of those bikes that will be easy to do as it's pretty basic and doesn't have a lot of "features" to deal with in the restoration.  Mostly, it will just need some cleanup and a repaint.  I already found the tank decals and I have the black paint from another project..  I will have to see what happens when I try to clean up the chrome.  There isn't a lot, but it will be expensive to get done.  I want this to be a budget restore.  Like that will happen :)

Updates will happen as appropriate.