KA Junior Classes Merge

Karting Australia has today announced a restructure of its junior classes that use the IAME KA100 engine. For next year, the KA3 and KA4 classes will essentially merge into a new-look KA”3.5″ class using a new 22mm exhaust restrictor.

Whilst retaining the KA3 name, engine performance for the consolidated category falls roughly mid-way between the current KA4 and KA3 specification.

From January 1, KA3 Junior will have multiple weight divisions; Light, Heavy and Championship, though as yet no numbers have been made public.

While KA4 will be dropped from AKC, clubs will still have the option of running current-spec KA4 under specific state regulations.

The new 22mm restrictors are currently being manufactured by IAME in Italy. Importantly, while it’s the same size as that used in the United States, it is a different design.

“It’s not the American one” IAME distributor Remo Luciani told KartSportNews.

“The restrictor used in America has a curved taper. We’ve already learned here in Australia that people were letting the carbon build up in the curve, and going faster.” (Ed: which is why the KA4 restrictor changed a few years back).

“That won’t happen with the straight taper in these ones.”

Remo confirmed the retail price will be under $100.

The full KA press release is below. Importantly, it relates only to the junior classes using the KA100.


Following a recent review, Karting Australia has finalised a restructure of its Junior Classes using the IAME KA100 engine. Effective 1 January 2023, a new 22mm IAME OEM Restrictor will replace the 19mm restrictor that has been used in the KA4 Class since the introduction of the IAME KA100 engine at the start of 2015.

It has become evident over recent years that the 19mm exhaust restrictor creates some issues with the tune-ability and performance of the engine in the Class. This has hampered the participation numbers in the KA4 Junior ranks. 

A similar 22mm IAME restrictor has been used with considerable success in American competition for the Junior KA100 class since the engine, initially designed for Australia, was adopted for US competition several years ago.

“IAME are supportive of the move by Karting Australia to introduce the 22mm restrictor into Australian competition and therefore bringing the specification of the KA100 engine for the Junior classes in line with other parts of the world,” said Australian IAME importer Remo Luciani.


“The Junior KA100 class in America is very popular and provides a great grounding for the junior drivers as they progress through the sport.  In the long run, I believe this change will be a positive one for newcomers and experienced drivers alike.”

The introduction of the 22mm restrictor will allow Karting Australia to streamline the junior pathway thereby encouraging higher participation numbers across the Junior Classes. 

“KA3 Junior will become the main junior development class and will incorporate Light, Heavy and Championship divisions at the respective levels of the sport,” said Karting Australia Chief Operating Officer Lee Hanatschek.

“Feedback from the membership base and industry on the KA4 classes over the past few years has led us to investigate ways of improving the experience for the competitor and industry alike.”

Mr Hanatschek has conducted significant research and overseen testing in consultation with the karting industry and KA100 engine manufacturer IAME and their Australian importer Remo Racing and believes the introduction of a 22mm Exhaust Restrictor will be of significant benefit for Junior competition.

“We’ve completed dyno and track testing with the 22mm restrictor while also consulting with numerous members of the industry, all of whom are highly supportive of the change for 2023,” added Hanatschek.

Final Class Regulations, including minimum weights, for the KA3 Junior Class will be released with the 2023 National Competition Rules later this year.  It will replace KA4 Junior at SP Tools Australian Kart Championship level in 2023.

The new 22mm Restrictor will be available from Australian IAME importer Remo Racing, or kart retailers across the country in the coming months. Any State Association that wants to continue to offer KA4 for the immediate future will be able to do so under State Regulations.


What is the power difference between the 19mm and 22mm restrictors?
Based on testing it is in the vicinity of 1.8-2hp difference on a dyno, which relates to a lap time difference of approximately 8 tenths of second around a 1,000m circuit.  The most vital improvement is in the tune-ability and power curve of the engine.

Will KA4 Junior or KA3 Junior race at the Australian Kart Championship in 2023?
Unless a State Association wishes to include the KA4 Junior Class in their State Regulations for the immediate future, there will only be one Junior class (with multiple weight divisions) – KA3 Junior.  This will be contested at a ‘Championship’ weight in the 2023 Australian Kart Championship.

I currently use a kart with a 101 wheelbase, can this still be used?
There is no change to the regulations surrounding chassis, as per Technical Rules, Chapter 1, Rule 8, e) (ii) the wheelbase must be between 1000mm and 1270mm.  Testing has been completed on both a ‘101’ chassis and a full size chassis.

When will the 22mm restrictor be available?
The 22mm restrictor is currently in production by IAME and will be made available by Remo Racing throughout Australia in the coming months.

Can the current restrictor be updated to a 22mm restrictor?
No, for all Competition in the KA3 Junior class a 22mm OEM IAME Type 3 Restrictor is to be used.

Can I buy a 22mm restrictor from America to get a head start on testing?
No, the restrictor being introduced to Australia is being manufactured using the latest 5 axis CNC technology and has a straight taper similar to the Type 2 19mm restrictor. This design has proven to be much more consistent in performance and is superior to the restrictors manufactured using 3 axis technology. The new 22mm restrictor will also be clearly marked to differentiate between the two versions.