I have a 1275 engine that has done around 1000ks. When it first starts up in the morning the exhaust is clear. After a couple of minutes idling there is blue smoke out the exhaust. If you hold the the accellerator around 3000rpm, the exhaust is clear. If I pump the accellerator once or twice there is blue smoke. Why is there blue smoke at idle but not under revs?

Do you have valve oil seals (top hats) fitted on the exhaust valve guides?

have they gone hard or perished !

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'78 1275 LS (Under Repair, Dependant #1's car)
'72 GT Powered Clubman (Mine)... Under (re) construction

No seals fitted on exhaust valves.

Only Minis made mid 70s on got exhaust seals fitted.
[edit] And if running manganese bronze guides the exhaust valves can seize if seals fitted.
Mk1 S didn't have seals on exhausts, nor did Alfas, Fiats etc.
Note-
Edited re K Liners, as GR says they work fine with seals on for road use.

Have the guides been pressed in too far, if so the oil level can get above the guide and seep down the valve stem.

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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.

An old school test is to drive to top of big hill and on the way back down don't touch throttle, you can use brakes, but let it "engine brake" to bottom, then nail throttle to floor. Big puff of blue smoke usually indicates valve guide / seal problem.

Do you have a brake booster fitted?
What are the symptoms for a failed brake booster diaphragm?
I know you can get smoke, but not sure of colour and under what conditions.
Does the smoke smell like brake fluid?

Smells different to engine oil , more like burnt food.
The brake fluid level would keep going down and engine may run bad at idle due to air leak.

Brake Fluid burns White...believe me! I know

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"Show me the Mini!"

does this read as pulling in oil under vacuum? dad's car did that after he ran it in by driving like an old lady, after a decent thrashing it was fine

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did I tell you that I won a trophy?

I have been informed that with more k's on the engine the carbon will built up and stop the engine from smoking at idle.

That folklore `may?' be true if oil is coming up past the rings. But not if it's coming down the valve guides.
At this mileage, it should NOT be burning oil or blowing blue smoke. Check valve guides and seals. If rings, it would blow smoke under load.

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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.