400-4 Tappet Adjustment using thread pitch

[TwiggsiiieS]

There was a thread on this but got bogged down with electrical connectors.

Just got down to looking at this idea and can confirm that the tappet screw pitch on my 400/F is 0.5mm.

so 1/10 turn would be good for 0.05mm(2 thou).

Just bought a tappet tool too and is much easier! much!

The tappet screw stops quickly as it touches the valve stem, back it off 1/10 (36°), job done!

Or is it? Anyone see a problem with this?

[Nurse Julie]

Why not just use feeler gauges?. Alot easier than trying to work out 36 degrees of something hidden down in a black hole. Or, is it just me........And yes, i do use the perfect little tappet tool.

[Orcade-Ian]

I agree with the OP, and find it easier with a 36 degree back rotation after touchdown.  Yes, the purist engineers (like wot I am) can tell me that when you tighten the locknut it pulls the thread upwards and increases the clearance but on a good old half millimetre pitch Honda thread I ain’t bovvered.  Still think it’s better than juggling soot with a feeler blade.  Needless to say I made my own tool.

Ian

[TwiggsiiieS]

Well I have hands like bananas and little patience with a feeler gauge that's tricky to get in the right place down a black hole and then and then!

I was just gonna make 10 equal marks on the top of the tool, less chance of getting it wrong and paper thin gauge staying in the tool box in tact!

Just bought the tool from Honda Classics with a good knob to make the marks on.

Well I will check one to make sure.

[Nurse Julie]

Out of curiosity Ian, I will try the 36 degree rotation next time I adjust the tappets on Hettie, always willing to learn something new. (Don't tell Trig I'm going to try your way, he will give me a lecture on the threads being pulled up on tightening 😭😭😭)

[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