Lambretta

1968 Li125 S

Getting it running II

Since I plan to tune this bike I just wanted to spend the least amount of money to get it going so I can put-put around the city and save my cash for the new engine parts. I took the nasty barrel and piston down to SF Scooter Centre and they really helped me out. Barry let me look through a box of used LI 125 pistons until we found one that was the right bore diameter, had decent ring pins, and wasn't scored up too badly. He then took a drill operated honing tool to the bore to clean it up and even got rid of most of the crud filling up the exhaust port. I also picked up a new head and base gasket for the barrel and he charged me only $18 for it all!!! His point was that if I just rebuild the top end and it didn't work there was no real loss except my time and less than $20.

  • When I got the barrel into a neighbor's garage I decided to clean out the ports as best as I could. We started looking for some way to clean the ports down to bare metal and decided to sand blast the ports while protecting the bore with rags. This is probably not a good idea to do after the honing but I managed to keep the bore protected.
  • I also took some emery paper to the port openings to slightly radius the edges just to be safe. The result was a nice clean port as shown below which is a great improvement from the original shown here.

On closer inspection, it looked like the original piston had fractured at the upper ring pin and lost the entire upper ring presumably through the exhaust port. This bike really didn't look as if anyone had worked on it since the dirt was extrememly thick all around the engine so I am guessing this is what caused it to sit unused for so long. The piston I got from SF Scooter Centre was used and had the usual carbon on the crown and small scoring around the exhaust port. I scraped off all the carbon with a scrap piece of wood and then polished it with metal polish. I removed only the high spots in the piston scoring with 400 grit emery paper. New and old pistons are shown below

After adding some gas/oil and draining and refilling the gearbox it started right up and we were shooting up and down the road past all the neighbor's dirty looks. Nothing like a two stroke going up and down the same street over and over to get people pissed off!

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