Posted by: scootswla | 03September'10

Guess who’s BACK

Way back in December of last year I started rebuilding my Kymco People 150. (Catch up here, here and here) I installed a NCY big bore kit but a few snags came up and with plenty of Vespas to work on the Kymco was put on the back burner.

Recent developments (ie blowing up the Red Vespa) have given me the opportunity to return to the People project. I had to bore out the cases to install the big bore kit and taken much care in the reassembly or the engine and re-installation of the engine into the scooter but to my disappointment she simply would not start. There was spark, seemed to be plenty of fuel, that only left compression. I checked and rechecked the timing marks and everything lined up like the manuals said they should. I should interrupt for a second here to say that this is the first four stroke engine I have worked on. Not that I’m a two stroke genius, or even competent mechanic, but four stroke was a whole ‘nother ball of wax. Finally it dawned on me, “it’s gotta be the VALVES”, and it was. Unlike the two stroke engines I had come accustomed to, with rotary induction, this engine had valves. Overhead valves to be exact. These valves open and close by way of the cam shaft, opening the intake valve during the intake stroke and opening the exhaust valve during the, you guessed it, exhaust stroke. (see a four-stroke primer here)

Once again I removed the engine from the scoot and took off the head. I don’t know why I didn’t see this the first go around, other than I wasn’t looking. I removed the valves from the head to inspect the valve seats.
Yuck! The carbon you see (the black stuff) is bad enough but notice the small silver dots, thats aluminum from the piston smeared all over the valve seat. A careful cleaning and it looks almost new.

For those of you who need a little help with the orientation of this photo this is the inside of the combustion chamber and the threaded hole is where the spark plug goes. the valves have been removed. The four outside holes are for the engine studs that hold the whole thing together.

The valves also needed some attention.

After all the surfaces were cleaned the valves were fitted, without the springs, along with some valve grinding compound, and carefully rotated in place against the valve seat to assure a tight machine seal. when I was satisfied that the mating surfaces would be tight, all parts were cleaned again and reassembled.

With the engine back in the scooter, a little fresh fuel with seafoam, and a little luck she ticked over and is running like a top. Now for the slow miles to break in the new kit. I’ve already made a few other improvements, but you’ll have to wait for another time to hear about those.



  1. What tool(s) or substance(s) did you use to clean the head, and the valves? Man, they look brand-shiny-new!


  2. I used a brass wire brush in a dremal tool and valve grinding compound. Carb cleaner or break parts cleaner was used to rinse all the grit away afterward, before re-assembly.

  3. Where do ya get that grinding compound?
    That’s beautiful work, Paul!
    Angela would be proud of ya 🙂


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