Sunday, 13 March 2016

One from the workshop: lathe adapter for cylinderhead work

The nice thing about two-strokes: very few moving parts and lots of tuning potential. The downside: Lots of things going wrong. One of the most pivotal points in making reliable power in any internalt combustion engine is the correct amount of squish.

In order to rectify the squishband width and height on two aircooled RD350 heads, I had to knock up this little tool.

Now you may (quite rightfully) point out, that this tool seems a bit excessively complicated, with all the lathe work and welding, but (and that's a big one) one of my lathe gears has spit out two teeth in the past and so I can't cut threads on the lathe...

But let's start at the beginning. Let's start with one sparkplug minus it's ceramic insulator.
Next was to turn a shaft on the lathe that is a light press-fit in the sparkplug.

Chamfer the lip of the old sparkplug to make pressing the shaft in a bit more easy.
E Presto:
After welding it up (see first pic) it had to be trued up again...
Runout is absolutely brilliant (0.1mm 50mm away from the chuck)

Do some cosmetics to it and file in two flat spots so it can be undone with a 17mm wrench

And test fitted a head in the lathe - job's a good un'

And I am sure you want to see this baby spinning:

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