I'm working on a custom built trike based on a 1600cc Air-cooled VW engine.
I'm a specialist auto-electrician and these engines are a bit before my time so I'm struggling to work out what is wrong.
The engine has a Solex carb which requires two 12v feeds that are both present. Is has various vacuum ports that are blanked off.
The distributor doesn't have vacuum operated advance/retard. The points look new.
The engine runs fine when cold, leave it overnight and it runs, revs and drives perfectly.
When it is warm it has no power you can barely pull away, it also back fires extremely bad while accelerating.
The owner seems to think the engine has recently been rebuilt.
What would be causing this and why would it do it when hot?