SOHC.co.uk Forums > CB350/400

400-4 Tappet Adjustment using thread pitch?

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DayvW:
Hi,

I rebuilt my 400-4 engine last year - with much advice from many off this forum - and she's still running sweet as a nut (took her out for a first proper 2015 run yesterday - fantastic).  Well - my battery is duff I think (she cut out eventually and I had to turn the headlight off to kick her up and get home - will be testing the charging circuit later) ... but that aside all was excellent :).  But I digress. 

I want to check my tappets - and thought I'd try the technique I read about somewhere that sounds really neat - ie. knowing the pitch of the adjuster thread, simply turn the required number of turns - or fractions thereof).  But I can't find where I read this - and importantly what the thread pitch of the adjusters is.  So - has anyone tried this?  Would you recommend it? And what is the pitch of the adjusters?

Many thanks.

Bryanj:
One full turn of the adjuste is 1mm or 40 thou so 1/8 turn is 5 thou

DayvW:
So a 1mm pitch thread then .. perfect - many thanks.

mike the bike:
It's finer than 1mm, don't know what exactly.   It's a sound idea is that though.

Clem2112:
I once had the SPQR ?  tappet adjustment tool that used x clicks of turn for the common thread pitches on BMC and Fords. Really good for minis.

The thread on the Honda is quite fine.... Think I measured it at 0,7 mm ?
Sounds like it should work ..... Maybe if the threads are new?

When I tried the same approach described here for my 400/4 using the Honda adjuster and a ring spanner I found the slack or wear in the threads (even with new tappet screws) left me with a bigger gap. You need to back off to the angle required and hold it there while tightening the locknut and it isn't easy !
What I find works for me after many go's  is to lightly tighten onto the .002" feeler then lock up the nut lightly and re check.
Then turn the screw in whatever direction by a fraction and lock up the nut fully while resisting the torque with the adjuster tool.
Trial and error really.

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