Ariel Owners Motorcycle Club

The original publications recommend .002" end float. Dragonfly is recommending .005". Why the change?

Which bike would be involved here, it makes answering your question a little easier.

I am restoring a 1958 Ariel Square 4..

The Draganfly web site says "The crankshaft end float should be .003” to .004” on the front crank and .005” to .006” on the rear. Ariels only ever listed shims to increase the end float, not to decrease it; these may occasionally be found fitted outside the timing side main bush." This is what is quoted in the Waller book. Checking the later 1956 owner's guide I see that Ariel say .002-.004 for both cranks. It should be a small amount to ensure that the cranks are not nipped up but as little as possible.

My concern stems from twin cylinder BSAs who's oiling system is similar to the Ariel's; .006" is way too much, starves the left hand rod.

Big difference between BSA (including Huntmasters) and Ariel 500s and Fours is that the
former have decent sludge traps which the latter don't and the latter have oil seal washers
on the outside of the timing side bushes which the former don't. BSA didn't get round to
fitting them until the A70 twins. 6 thou end float on a roller bearing A65 is indeed an
impatient disaster.

The term oil seal washer is a tad odd; is there supposed to be any rubber on them? Mine, which appear to be original, are just plain steel. Did I mention that this is a bike in a box, disassembled in 1978?

No rubber. As you say, just plain steel but I think they only fit one way round.

The inside of the seal is beveled but it will fit either way.

The bevelled side goes inwards, towards the main length of the crank. The bevel is to cope with the tiny radius at the change of crank section.