A Home-Made Adapter for Timing a Two Cycle Engine

I recently installed a new set of points in my ancient 1972 Yamaha 175cc dirt bike (many parts are still available, which is amazing!), and that requires setting the ignition timing.

Years ago, I had a micrometer-type tool that screwed into the spark plug hole to help set timing. But somehow it escaped from the tool cabinet and walked away a decade or so ago, and I needed a way to measure the piston’s travel near top dead center, in .001″ increments.

It dawned on me that there are several common dial indicators in my shop that measure thousandths, and all that was needed was some sort of adapter to mount one of them into the spark plug hole.

Once again that handiest of tools, the old Atlas metal lathe (also pretty ancient, at 70!) made things easy. An old spark plug was cut off and its tough ceramic material removed – the hardest part of the job – and its ID drilled and reamed to 3/8″ to snugly fit the indicator’s shank. I planned on tapping in a setscrew, but that wasn’t necessary; the indicator stayed in place nicely without one. Anyway, here’s what the crude little adapter looks like mounted onto the indicator: 


 And on the engine head, doing its thing: 


 A handy little project that solved the problem, and is much easier to read than the old micrometer type gauge was.  I’ll probably add a setscrew in the future, but that job can wait. This is, I believe, only the second time in about 40 years I’ve replaced this machine’s points. 

Hope that’s of help to someone. 

I have to add this from the Gracie files, one of several really good ones my oldest daughter shared with me this week: 

“Dogs don’t ruin their sleep worrying about how to keep the objects they have, and to obtain the objects they have not. There is nothing of value they have to bequeath except their love and their faith.” – Eugene O’Neill

God bless you – and stay warm!

Dave Harnish

John 14:6


About Dave Harnish

I've been an appliance repair tech since 1972, with interests in most everything, including Bible study (I'm one of those KJV-only geezers), old Sunbeam Mixmasters, Maytag wringer washers, the outdoors, birds, hunting, metalworking, firewood cutting, and most anything going on outside on our mountain here in N. PA's 'Endless Mountains'.
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