Cracks when shutting throttle off

[Peterbertie]

So the non runner I brought now runs ticks over nicely hit the throttle and it picks up fine.
Sometimes when I after a big hand full  shut throttle off she gives of a bang I have noticed No1 downpipe takes longer than the rest to get hot. Carbs stripped cleaned new carb kit installed float height checked valve clearance done at a garage by previous owner in February it has a yosihimura exhaust omay be its the nature of the beast anyone had the same

[wraith]

Is it just one bang or lots of poping/banging when shut off?

Is it coming from the zorst?

You can get this if the carb mix is out or you have a air leak in the zorst.

Or a one off bang on shut off maybe something with ignition, 

[colinworth79]

I would balance the carbs with some vac gauges as it sound like no1 is slightly behind the rest.