To be honest, I never looked for the difference. Good catch. I'm guessing the absence of the numbers boss above the timing hole was the tip off ruling out '71.

 

I'll look for the "belly numbers" on the case (both sides). As I understand from link (below) provided by The Doctor 71, the number on each half of the case should (a) Match (but probably won't?), and (b) Start "771" if the engine is from a '71 Sportster.


https://sportsterpedia.com/doku.php/...:ih:engmech01b

 

Why does the lack of numbers boss above the timing hole rule of it being a '71? From what I am seeing from the links and info provided, the boss an subsequent VIN stamping on that side was no longer present from 1970-85.

 

Let me guess - stolen sportster, wrecked sprint, a file and a set of stamps?

 

Welcome to the forum. For 1971 model Sportsters I have photos of engine VINs in two different positions, both of which are on the R-H case, but the cases are different to each other. Some VINs are stamped where yours is but some are stamped further forward like I’ve seen for 1970 models. Because your VIN is so low, and if it began with 4A (or 3A), I may have expected it to be in the forward position although there may have been some overlap in this regard.

However, and as you discovered, 6A indicates a Model SS and not an XLCH. Also several characters in your VIN aren’t even consistent with factory stamping.

As indicated above, photos of belly numbers may help.
Eric

 

Correct.

• 900cc left side engine casting = 4 horizontal lines + a number boss
• 1000cc left side engine casting = 5 horizontal lines

As I indicated earlier, "Belly Numbers" are most likely the next step to revealing more.

 

Although the engine number was shifted from the left case to the R-H case as of 1970 models, a number boss remained in the casting of the left case for 1970-71. But the boss on the left case was omitted for 1972 and the number of ribs changed from four to five, as mentioned above. This may be when the left case casting number became 24534-72?

For 1970 models the engine number was usually stamped on a boss near the front pushrod tubes. Some 1971 models also had the engine number in that position but other 1971 models didn't.
Eric