It has been a while since my last post, nearly 1 year.
I promised to come back with an update, so here goes, and sorry for the wait.
Kicked the engine over 50+ times before I managed to start it.
Rode the bike for a rather short trip, but it was impossible to get it in 3rd gear, and there was a lot of white smoke coming from the exhaust. See how it looks when I rev the engine a bit:
Might be easier to to see here, a bit of footage from after having shut down the engine:
Thick white smoke, and the engine had a hard time idling with low RPM’s. Besides this, I was also struggling a bit with the wiring and the lights.
The turn signal lights stopped blinking after a short while, and gave me a constant light instead. Furthermore, the neutral gear indicator stopped working after a few km. Removed the left engine crankcase cover, and realized that that the indicator only worked when I moved the wire a bit back and forth, indicating a partly broken wire.
Finally, the headlight gave close to zero light, and the headlight switch didn’t seem to change a thing, no matter what position it was in.
A local electrician, who owns no less than two ST50’s, offered his help with the wiring. My job was to keep the engine running, while he did some measurements with his multimeter. He soon concluded that a few wires in the headlight bucket should be swapped, and that the wires wasn’t grounded properly. We removed the seat latch, scraped off a bit of paint around the bolt holes, and ran a wire directly from the battery and to one of the bolts. This ensured a proper ground, and all lightning issues were resolved, all but one at least, the unstable neutral gear indicator.
I also still needed to deal with the white smoke and the bad shifting.
The seller of the engine had stopped responding to my numerous requests for help, and wouldn’t even pick up the phone when I called him, so I decided to at least warn others about doing business with him, so they shouldn’t have to go through the same trouble as I did.
I made a Facebook post in the group where the seller originally contacted me, simply just telling my story, and asking others for help.
It only took a few days before I was offered to borrow a brand new reproduction carburetor, so we at least could dismiss this as being the root of all evil.
Besides changing the carburetor, I also tried changing the size of the fuel jet nozzle (#62 -> #68), but without any luck. Engine wouldn’t idle steadily, and a lot of white smoke still.
Checked for air leaks by spraying brake cleaner around the manifold, to see if RPM’s would rise, but everything seemed to be good in this regard.
Then I noticed this:
What appeared to be oil was leaking from the bolt in the cylinder, or the area surrounding it, not easy to see the place of origin.
I then checked for more signs of oil leaking, and found some more here:
I then realized that everything most probably had to be taken apart, and removed the exhaust.
Dark colored oil was dripping from the bottom of the engine head.
I then removed the cover on the cylinder head…
The next few days I was wondering about what to do next, knowing next to nothing about engines, but then the phone rang one fine sunny day – unknown caller ID.
It was the very same man that I 15+ years ago bought the frame and my first parts from. He had seen my post on Facebook, and wanted to offer his help. I immediately removed the engine from the frame, and we agreed to meet at his place a few days later. He used to run his own moped shop in the 70s and 80s, and had been repairing these small engines for longer than I had lived, so if anyone could help me, it would most definitely be him.
We removed the cylinder head and the cylinder as well, and it all appeared to be in decent condition. He then scraped off the remains of the old gasket, and then something caught our attention.
We removed some of the paint from the cylinder, and this is what we saw:
The cylinder had a very large crack, that the seller had tried to repair with some sort of heat resistant sealant, and then tried to hide with an extra thick layer of paint.
We continued the search for the next two hours for other unpleasant surprises, and sadly we found a few, even though this by far was the worst.
The timing chain tensioner arm was old and worn, and did not apply enough pressure on the chain. The gear shifter spring didn’t apply enough pressure either, making it nearly impossible to go into 3rd gear.
Tappet caps was of poor quality and made in China, not original ones as otherwise agreed. Bad functioning clutch mainly due to clutch plates with quite a bit of wear. Worn clutch guide, wrong clutch nut used, and damaged lock plate as well. Several washers were missing.
The list was long.
All in all; a very miserable job apparently made by a complete amateur. This guy wasn’t an amateur however, quite the contrary, so everything was taken care of. All unoriginal parts were replaced with new original ones, and the wire to the neutral gear was changed as well, making the indicator light work as intended. Finally the engine was restored to it’s former glory.
Next up will be video or pictures of the little machine in running condition, and a few closeups of the engine.