Linkert M5’s 1936 - 1939 INFORMATION

The Linkert carburetor M5 used for the first time on Harley-Davidson’s first Overhead Valve (OHV) the 1936 Knucklehead E, EL is without a doubt the single most valuable brass Linkert carburetor ever made. And out of the four known (but not always agreed on by the experts) variants, the 1936 M5 with the two-bolt intake flange is the most sought after of the M5’s with values of just the carburetor body in the $5,000.00 dollar range. (Note that this is true for the brass Linkert’s produced, the most valuable Linkert would be the M25R which is an aluminum Linkert carburetor, perhaps only two made for the factory for their race team.)

Regardless, all the M5’s used on Harley-Davidsons from 1936 to 1939 Knuckleheads E, EL appear the same with some exceptions. They all have M5 stamped on them, 4 lines of manufacturer’s information, they all are 1 ¼ Mod M with 2-348 on the bodies and like all 1939 and before Linkert carburetors the bodies and small parts were nickel plated. The 1936 and 1937 have MOD numbers 2-348 and the “4” is hand stamped, while the 1938 to 1939 all the MOD numbers 2-348 are cast.

The exceptions are that the 1936 M5 has only the two-bolt intake flange, and the 1939 M5 uses a Type Two fuel bowl. Other exceptions are in the carburetor’s attachments like the air cleaners, and the fuel filters. (All the 1936-1939 M5’s used the same throttle levers, and the same carburetor supports.) Only the 1939 M5 used a different fuel filter. The 1936 M5 used a 6” round air cleaner without the bar and shield logo stamped on the cover and used a two-bolt backing plate (Note that a four-bolt backing back won’t work on a two-bolt carburetor intake flange it leaves two of the holes exposed, NO DOCUMENTATION ON THIS*). The air cleaner also used 4 cadmium 8-32 screws through holes (not the ‘J’ slots), the 1937 was the same only using a four-bolt backing plate and the bar and shield stamped on the cover. The 1938 and 1939 M5’s used the ‘J’ slot to attach the air cleaner cover and a spring was added for tension against the ‘J’ slots rivets.

* This is an issue. I have never seen in any book or documentation nor in person, and not anyone has expressed any knowledge of any two-hole backing plate either for the 6” round air cleaner or for the 1936 air snoot? Why is this? I have seen 1936 Knucklehead EL’s restored and in auctions and museums with the 6” round air cleaner, however they didn’t have the two-bolt intake flange on the carburetor’s body. So, is this one of the over-lap mysteries? Is it possible that the early 1936 Knuckleheads two-bolt flange carburetors still had the two-bolt air snoot (the two bolt heads exposed) longer style? OK but then again Where are the right-side air snoots like that? So common sense would indicate that there are two-hole backing plates out there? Somewhere.

Now let’s review the information about the variants. Bruce Palmer III’s book (liste,d on this website) doesn’t discuss the variants and just lists the M5 used for 1936 thru 1939 E and Els. Mike Aldrich, owner of Into The Wilderness at parts@Linkertcarbs.com (also listed on this website) who has the most comprehensive carburetor and their variants listed (this list will be revised in the future), has reviewed the two M5’s on this website and determined that they are a 1937 and the other one is a 1938-1939 and they are presented as such on this website.

Please note that it is just because of the importance of the development of the Overhead V-twin Knucklehead that Harley-Davidson produced those other differences in the carburetor’s body that help with determination of the variants. In this case with regards to the bowl stem modifications that help determine the variants of the M5.