Tappet adjustment - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 7 (permalink) Old 07-14-2019, 10:54 AM Thread Starter
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Tappet adjustment


I've just fitted a set of copper coated, allen key, mushroom head tappets to my 64 3TA.

How do I set the gap, there is no way I can see to do this visually. On the old ones you could just turn them one full flat & that would set the gap.

Any suggestions on how to set these type please?


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post #2 of 7 (permalink) Old 07-14-2019, 11:14 AM
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You are unable to turn the adjusters back 90 degrees, because they are not square?

Anyway, a full flat on the original square topped adjuster is about 0.008”, just for interest.
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post #3 of 7 (permalink) Old 07-15-2019, 05:43 AM Thread Starter
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These new tappets are round, this is what makes it difficult to set them.

I can't be the only person to have these fitted?


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post #4 of 7 (permalink) Old 07-15-2019, 09:09 AM
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Unless Iím misunderstanding the issue, you put the hex key (Allen wrench) in the hex and make contact with the valve then move the wrench handle counter clockwise 90 degrees which would be the same as one flat on the old type square head.
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post #5 of 7 (permalink) Old 07-15-2019, 01:34 PM
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I don't understand either.
I have allen headed tappets on my t140

Loosen the tappet, slip in the feeler gauge, tighten the tappet using the lawn key and nip up the nut. Remove feeler and re insert it to check
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post #6 of 7 (permalink) Old 07-15-2019, 03:32 PM
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All adjuster tips are round, though their roundness may be of different radius.
The thread of the adjuster is still the same as it ever was (26 tpi BCY/CEI) in your case most likely. much later they changed to 24 tpi.
For either of these threads it is good enough to assume 40 thou for each full turn.
So you can use the "contact and back off" technique or feeler gauges, according to your preference. It doesn't make any difference, except if using feelers you may have to make a longer kink at the end of the blade.
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post #7 of 7 (permalink) Old 07-16-2019, 12:24 PM
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They are a bit fiddly to set with feeler gauges, thats why the side plugs on the rocker boxes came on the late engines. I usually set my intakes to "barely perceptible movement" and exhaust to "faint click" instead
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