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400-4 Tappet Adjustment using thread pitch

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Orcade-Ian:
When I were a lad (stop yawning at the back!) there was a tool for Minis which had a 1 thou per click system. It was made by SPQR.  If there was any error when the locknut was tightened, like our Hondas, it gave a tad more clearance, so no chance of burning a valve or seat.

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The hole in the end was drilled deep and filed out to a square with a needle file.  The knurl on the end is just to make it easier to turn and the two long marks on the waisted section are 36 degrees apart - done on the dividing head.  You nip the clearance up gently, noting the mark against some fixed point and back it off to the other mark - simples!

TwiggsiiieS:
Thanks orcadian, yeah a bit more clearance at least its on the safe side.

Thinking about it, when the tappet screw touches down any slack, slack in the thread will already be taken up, mark noted on a fixed point and when you back it off 1/10,  the lock nut, although tighter, cant pull it up very much more.

Well that's my theory, will try it and check it out with a DTI gauge!

Steve

ka-ja:
It is not only "slack" that takes up when securing the lock nut, the tappet itself has a tendency to turn with the nut is hardened tight, decreasing the set clearance.

Orcade-Ian:
That’s why the rod is knurled and you are watching for movement of the line but you can do it your way too of course.
Ian

TwiggsiiieS:
Take your point Ken, that happens with feelers as well but as Ian says you can hold tight with the knurled bit and watch your mark as you tighten.

Steve

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