valve clearances

[mugwump]

 As a matter of interest, does anybody know if the valve clearances get bigger or smaller as the engines heats up. This in relation to an iron head and steel push- rods.
thanks

[Worty]

Don't you just set them cold and not worry about it.

[Worty]

I guess you know you've got it wrong when a pushrod appears through the casing.

[Topdad]

Wortluck , guess that would work for me !! lol

[Swarfcut]

 The valve must close completely when the engine is hot, in other words a  tappet clearance must exist. Automotive practice to achieve this varies from engine cold, engine hot or even on Pre-War Vauxhalls, engine running. Lots of time, effort, calculation and experiment was carried out by the R & D departments of the manufacturers, we reap this knowledge from the published data.

 It's academic really, tight set tappets, goes like stink, quiet, burnt out valves. Wide set tappets, rattles, sluggish, hammers the valve stems, valve seats last forever.

 Take your choice.....Gimme hydraulic tappets any day.

 Swarfy.

[Worty]

The valve must close completely when the engine is hot, in other words a  tappet clearance must exist. Automotive practice to achieve this varies from engine cold, engine hot or even on Pre-War Vauxhalls, engine running. Lots of time, effort, calculation and experiment was carried out by the R & D departments of the manufacturers, we reap this knowledge from the published data.

 It's academic really, tight set tappets, goes like stink, quiet, burnt out valves. Wide set tappets, rattles, sluggish, hammers the valve stems, valve seats last forever.

 Take your choice.....Gimme hydraulic tappets any day.

 Swarfy.

Hey Swarfy

I always set my tappet clearances quite wide, as BSA say to extract max power from the motor, clearances of .010 inlet and .016 are ok.  Engine is a bit clattery, but given that the clearances close up a bit when hot, it seems to work very well and bike goes very smoothly.  Am I to assume I'm battering the life out of the stems??

Incidentally, with the Kwaka W650 I've bought, the valves are actuated via bevel drive which, I'm told, is way smoother/reliable/quieter/durable than chains and pushrods.  If this is the case, why aren't more bikes built in this way??

 

[mugwump]

I appreciate all thats been said, and thanks again. I do understand the need for appropriate tappet clearances and the problems with incorrect settings etc. I simply wanted to know whether the clearances close up a little or open up on the all iron engine. The settings on my AJS 18s are set nil with a warm engine, but that has an alloy head and push-rods.