I put 20W/50 in my twin HS2s at first and could barley move the pistons at all. So I added sewing machine oil and that freed it up a bit. How easily should they be able to move? (With the piston damper still screwed in)

a sort of related question on this topic,i took the twizzle stick thing out of my dash-pot and it appeared to have oil at the end of it,how much oil should be in there ,do i fill it to the top ,and whats the oil for,

OK last question first..
The oil is there to damp the upward movement of the piston when you open the throttle. This richens the mixture for a moment, sort of like an accelerator pump does in other carbs.
You should fill just to top of piston rod....

How easy should it move? You want some restriction, but IMO 20W/50 is a bit too thick, particularly in Winter.
I've now put some 3-in-one oil into Barney's twin HS4s, we'll see how that goes.
ATF is also very popular.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

my carby guy reckons ATF or dexron III like the doc says


i have been using snapon air tool il which seems to be doing the job
perfectly for me.

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Cheers Steve.


1973 south african mk3, 1275 +30 (1300), RE13 cam, hif44, mildy worked head with s sized valves, pulsar dizzy, 1.5:1 minispares forged rockers.