20cc Four Stroke Diesel

[Roger B]

I was planning to use pieces from my milling clamp set to hold the crankcase and cylinder block together for spotting but the slots were not quite long enough. They were opened out in the mill using one of my recently won 8mm roughing cutters. The pieces were aligned and clamped together, the spotting was near the limit for my bench drill but worked. 80mm stroke was just enough. The holes were then tapped M4 and I cut some blanks for the fixing studs.

[Roger B]

I decided to thread these under power, but I know that at 250 rpm the Hobbymat has quite a long run on period so I couldn't use a fixed stop. A tool shank made a suitable aiming mark and all 5 were successfully made. The holes through the block were then opened out to 4.5mm and those in the head to 4.2mm. It all fitted together and allowed me to check the cam chain length and alignment. All looks OK 

[Brendon M]

Hello Roger, I look forward to seeing this run

[Roger B]

Thank you Brendon, you may have to wait a little while 

The next stage was a slow lapping of the cylinder liner to the same diameter as the two stroke diesel. I use an Acro Lap and 40 micron diamond paste. I kept on until the plug gauge from the two stroke engine was a snug fit and then checked with the piston and spare piston rings from the two stroke fitted.

Next step is the piston.

[Admiral_dk]

Great to see that you still make progress and nice piston ring to cylinder fit     

Per