Linkert M53 series & mr series

There are differences with the M53 series carburetors that are unlike any other Linkert M models.  All the M53 series Linkert carburetors have a ‘coned’ backing plate instead of the usual ‘flat ’one.  This ‘coned’ backing plate for the air cleaner also has a unique bracket riveted on for the horn.  And all the Linkert M53 series carburetors also have a unique choke shaft and lever that is different from all other Brass Linkert carburetors.  The M53 has a two-piece choke lever shalt, and the M53A and the M53A1 both have a single choke lever shaft.  The  M53A and M53A1 carburetors have a unique choke disc that isn’t inserted into the choke shaft like the other Linkert carburetor but has an ‘indentation’ that mounts on the outside of the choke shaft, (the M53 has the usual choke disc that inserts into the choke shaft).  The M53 and the M53A both have ‘J’ slot 7” air cleaner covers and the M53A1 has a center screw 7” air cleaner cover. This center screw 7” stainless steel air cleaner cover is secured to the backing plate with another unique to the M53A1 a ‘shorter’ center screw bracket.  All the M53 series and the MR series have a 10-32 plug with a hole through it installed in the Idle casting of the carb body. See the photos below.  ALSO: See page: Linkert Bombsite vs Standard venturi.  (You might look at the similarities between the M53 series and the MR series of brass Linkert racing carburetors.)

The MR series is unique in that it doesn’t have a choke shaft so there is no place for a choke disc.

M53A, this carburetor has no official documentation that it was ever installed on H-D factory production K models.  And the M53A came with both duel and single venturi. However, it is so similar to the other M53 series that it was most likely a half year installation on some of the factory production K model series motorcycles. 

Note that the M53 series carburetors also have some of the same unique characteristics with the MR series of racing carburetors like the bombsite venturi, and the set screws with spring, also the High speed and Low speed needles. And the unique 10-32 plug with the hole, installed in the idle needle casting on the carb body. So that as far as the M53A’s usage goes. It was used by some of the factory racing teams, but no one really knows.
See:  Mechanics Reference pages.

There were quite a few different models of the K series flat head during the years 1952 and 1956 when the K models used the brass Linkert M53 series carburetors, and some were in racing and hill climbing configuration.  And the MR series racing carburetors were also installed on K models as well as other Harley Davidsons.

And another unique thing to the M53 and the MR series., they are both four bolt mount carburetors. You will find that the M53 series and the MR series share the same K model type of four bolt manifold, so really it could be referred to as the MR type of manifold, The manifold fits the SV or side valve flathead, yet it will bolt up to any four bolt carburetor.