The II series completed the remainder of the first order from the Czechoslovak Government, These were 45 aircraft numbered B-534.102 to 147.
Like the I series these carried four guns.
However the solution to the problems with the wing-mounted guns was to move these guns, now upgraded to the vz.30 to the fuselage with the others.
The four 7.92 mm (0.312 in) machine guns were located on the sides of the fuselage, firing through the propeller.
One very modern innovation was a bubble canopy; this had been tested on a small number of the early series aircraft, although it certainly was not a standard fit.

During 1936, a second order for 46 aircraft were issued by the government.
The first 25 of these were the B-534/III version serial numbers B-534: 148–173.
Production took place in the second half of 1936.
It entered service between March and April 1937.
The III series had aerodynamic refinements which saw the streamlining of the front carburator air intake.
Mudguard spats were also often added at the factory to the main gear.

The remainder of the second order from 534.174 to 534.193 were the IV series.
With later orders the fourth series would occupy the serial numbers .174 and 445 and was therefore the most numerous of the types.
The most important change to the earlier series was the enclosed cockpit.
The IV series also enjoyed a metal light alloy Letov (Hochfeld) Hd-43 propeller.
The various refinements allowed the IV series to have an increased speed of over 200 mph, and this placed it on par with the best of its contemporary biplanes.
A common alteration to the IV series was the replacement of the tailskid with a tailwheel.
Operational experiences had shown that the spat on the main landing gear could become clogged with mud on grassy airfields and cause takeoff and landing problems.
The spats were then often removed.

During 1937, the superb performance of the B-534 was demonstrated at a flying exhibition.
The aircraft was tested against the best in the world at the IV International Air Meeting at Zurich's Dübendorf airport.
The B-534 entered three of the competitions.
The first of these tested climbing and diving.
A GermanBf 109 took first place and a Henschel Hs 123 pilot pushed his biplane to claim second.
The B-534 took the next three positions.
The 534 outflew every other fighter participating, bar the Messerschmitt Bf 109 – and even then, the Avia was only 11 km/h slower than the German aircraft.
Four subtypes were produced during the B-534's production run, all with mostly minor improvements.

Allegedly, problems were encountered with the redesign effort to adapt to installation of a newly installed cannon.
These were not resolved in the summer of 1938; by this point, Czechoslovakia, sensing rising political tension amongst German claims to Czech-held territory, was eager to get more aircraft in the air, Avia decided to use a third machine gun in the nose.
 Judging by the size of the gun magazine, the nose machine gun was matched with an increased supply of ammunition.
For the nation, time was running out and drew to Munich Diktat, at which point Germany commenced its occupation of the Sudetenland (the western border area of Czechoslovakia).
Two series were produced Bk-534, cn's 501 – 554, and cn's 555 – 620.
Only three of the second batch were completed for the Czechoslovak air force, and the remaining 63 aeroplanes from this production block were finished for the Germans, after the German invasion of the remainder of Czechoslovakia on 15 March 1939.
The II series completed the remainder of the first order from the Czechoslovak Government, These were 45 aircraft numbered B-534.102 to 147. Like the I series these carried four guns. However the solution to the problems with the wing-mounted guns was to move these guns, now upgraded to the vz.30 to the fuselage with the others. The four 7.92 mm (0.312 in) machine guns were located on the sides of the fuselage, firing through the propeller. One very modern innovation was a bubble canopy; this had been tested on a small number of the early series aircraft, although it certainly was not a standard fit.
During 1936, a second order for 46 aircraft were issued by the government. The first 25 of these were the B-534/III version serial numbers B-534: 148–173. Production took place in the second half of 1936. It entered service between March and April 1937. The III series had aerodynamic refinements which saw the streamlining of the front carburator air intake. Mudguard spats were also often added at the factory to the main gear.
The remainder of the second order from 534.174 to 534.193 were the IV series. With later orders the fourth series would occupy the serial numbers .174 and 445 and was therefore the most numerous of the types. The most important change to the earlier series was the enclosed cockpit. The IV series also enjoyed a metal light alloy Letov (Hochfeld) Hd-43 propeller. The various refinements allowed the IV series to have an increased speed of over 200 mph, and this placed it on par with the best of its contemporary biplanes. A common alteration to the IV series was the replacement of the tailskid with a tailwheel. Operational experiences had shown that the spat on the main landing gear could become clogged with mud on grassy airfields and cause takeoff and landing problems. The spats were then often removed.
During 1937, the superb performance of the B-534 was demonstrated at a flying exhibition. The aircraft was tested against the best in the world at the IV International Air Meeting at Zurich's Dübendorf airport. The B-534 entered three of the competitions. The first of these tested climbing and diving. A GermanBf 109 took first place and a Henschel Hs 123 pilot pushed his biplane to claim second. The B-534 took the next three positions. The 534 outflew every other fighter participating, bar the Messerschmitt Bf 109 – and even then, the Avia was only 11 km/h slower than the German aircraft. Four subtypes were produced during the B-534's production run, all with mostly minor improvements.
Allegedly, problems were encountered with the redesign effort to adapt to installation of a newly installed cannon. These were not resolved in the summer of 1938; by this point, Czechoslovakia, sensing rising political tension amongst German claims to Czech-held territory, was eager to get more aircraft in the air, Avia decided to use a third machine gun in the nose.  Judging by the size of the gun magazine, the nose machine gun was matched with an increased supply of ammunition. For the nation, time was running out and drew to Munich Diktat, at which point Germany commenced its occupation of the Sudetenland (the western border area of Czechoslovakia). Two series were produced Bk-534, cn's 501 – 554, and cn's 555 – 620. Only three of the second batch were completed for the Czechoslovak air force, and the remaining 63 aeroplanes from this production block were finished for the Germans, after the German invasion of the remainder of Czechoslovakia on 15 March 1939.
Avia B-534