A65 Running Lean

Nov 17, 2023
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My A65L is running very lean but will run well with the choke fully on.
Choke off and it dies.
Should the inlet valves be close at BDC?
Mine only start closing on the compression stroke when the piston starts to rise.
Upshot is there is blow back of some of the mixture in the cylinder through the inlet port.
Is this the cause of the lean running?
Is the valve timing out?
The bike has recently been fully rebuilt (by others) and I'm first to put any miles on it.
The inlet valves close quite a long way after bottom dead centre. Could be more than 60 degrees after. What you are seeing sounds correct.

Do you know which direction your choke control works? The lever pulls the cable to raise the air slides for normal running.

If you are not operating the choke backwards, then needing choke to run can mean blocked pilot jets or air leaks into the inlet manifold.
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Plus check your tappet clearances, a tight inlet clearance will extend the valve opening slightly.
Thanks guys.
Yes, the choke is operating correctly and the valve clearances are correct.
I had the pilot circuit down as a possible cause. The carbs are originals from 1971 without the access screw opposite the air screw so difficult to get at the jet from the fuel side.
I've got new carb bodies with the removable pilot jet. I'll put them on and see how it goes.