Air Cleaners

Back to change notice

The most commonly mentioned  Air Cleaner is the "Vokes" filter (refering to the manufacturer). There were however more designs.

The first filters found on 30 ties type Norton motorcycles are seen on bikes destined for Palestine and India . These bikes show a biscuit tin like round box, mounted at the right hand side of the rear wheel. The wheel itself is valanced with a sheet of metal, most likely mounted in the same way as later seen on the lefthand front side of the Big 4 combinations. The valance obviously serves as a shield to deflect stones and dirt in general from reaching the filter.  This filter is described in 1936 spare parts list (contract C8753) with Norton numbers. The Cleaner was described in the Norton Assembly books as "Vokes C1a Protectomotor Air Cleaner", so it was obviously made by Vokes.

(IWM HU93246)      

Left: 1936 16H most likely destined for Palestinenad or India, likely from Contract C8753.  Right:  Bernhard Hope in 1942 after Alamein. The bike still sports the tubular Air Cleaner first seen in 1936!  Was this one of those bikes destined for Palestine? Only the speedometer is additional to the pictures of 1936.
"He was riding East to Sidi Barrani from Tobruk, Libya, and he was doing at least 60 hence his ANZAC slouch hat hanging round his neck" (remark from the photographer).


Picture left: Possibly a picture from a bike as proposed for an "India" contract. It shows the 1938 engine (no oil tell tale), upswept silencer, large crankcase shield, front mudguard stays with lifting handle, pillion seat, saddle with knee padding and lugage carier, all given in a 1939 spare parts list (Government of India contract Y6730/8279).  Contrary to that spare parts list however, it still shows the earlier round dust filter.

Picture right: A tank top Vokes Air Cleaner on a pre/early wartime production machine, also sporting a petrol tank with the rear end cut-off to facilitate the hose. It seems that this is not a machine as initially described as India machines. The picture came from Australia, but the provider could not tell much about it. It has the oil tell tale indicating it to be the 1937 spec engine. It shows to have a fixed, one piece, elbow, contrary to the later types using an adjustable 3 piece elbow. The bike itself is as made upto October 1940.

The first mention of a "Vokes Air cleaner, modified" is found on 15th of November 1937 in relation to bikes for the Nizam Forces in India. Athough there is no description of the filter, the addition of "Modified" may be referring to the Vokes Tank top filters. An even likely explanation of "modified" could be the C1a denomination of the biscuit tin Air Cleaner. Norton had the habit of identifying  modified parts with a suffix "a". No mention of a modified petrol tank as well in 1937. The first rather certain indication for the Tank Top mounted Vokes is seen on pictures of a prototype Big4 machine (Military reg C385695) of 1938 which is clearly provided one (below, left hand picture). It also shows the right rear end of the tank being cut-off, and fixed non adjustable straps to the kneegrip screws and non adjustable elbow to Carburetter. The right hand picture shows the Air Cleaner mounted on a later 16H bike with adjustable fixing straps and elbow.


The spare parts list of the Norton Contract S5161 shows a VAOS (Vocabulary of Army Ordnance Stores) parts number MT12/NC/11783 for the Air Cleaner complete.
Within the VAOS spareparts system, part numbers with NC are Norton spare part numbers. Even the Airfilters described in a Arial WN/G spare parts list refer to these same VAOS numbers (as also shown in the latest book of O&M). 

The consistent reference to Norton suggests a strong link between the design and Norton. As Vokes was a renowned air filter manufacturer, it is most likely that they either did (participate in) the design for Norton, or the Norton design was taken over as is, in the end becoming the "Universal Air Cleaner".

Click on the picture to enlarge.
Exploded view of the early biscuit tin Air Cleaner Connection tube flexible clamp fixing tube to saddle stud connection between Carburetter and tube
VOKES EARLY (As used on Nortons and possibly other makes)
  Notice the non adjustable straps fixing the filter to the rubber kneegrip bolts and the fixed elbow to fit hose to carburetter.
VOKES LATER (As used on various makes)
Topview     Identity plate Bottom view     Bottom view inside  
elbow piece assembled (HJ)
Adjustable Elbow Piece assy.
Elbow piece individual parts (HJ)
Elbow Piece Parts
Vokes with canvas cover (on BSA)

Pad, Air Cleaner Protector MT12/NC/1212927

Some history on the Vokes firm can be found on



A little known Air Cleaner was the "Talflow filter", a product made by the "Talboy Manufacturing company Ltd". This firm was actually also a subsidiay of Shelley. Shelley was the parent company of Norton Motorcycles. Saying goes that Talboys also made sheet metal products for Nortons. The most probable reason for this air cleaner to be relatively unknown is the fact that they were "bombed out of existence" in the early war years.


The Talflow filter on a BSA M20



Talflow sideview lid removed

Talflow front view lid removed

Talflow rear view

Talflow quarter front view

Talflow front view