Date coded parts and when they would be used

[Taylorfromtucson]

This isn't entire flathead specific, but I have been building a 1946 45 flathead and am trying to be specific to the year. I didn't know what they odds of finding a reasonably priced survivor, soni decided to build one. The motor I just picked up has a late 3000# vin...so it is a wl39xx. I know that after the war there were a lot of surplus parts used tht were made earlier than the previous year. Around what year/month/??? Should my date code be to have it match correctly with the vin on my motor? I found an April 1946 tranny online and wondered if I should get it(I already have a tranny that works, but I am stuck on building a bike that would have come out of the factory in 1946). Thanks in advance

[Rubone]

Many factors at play with date codes. Cylinders were often as much as 6 months before VIN dates. Iron castings are aged before machining. What are the date codes on your cases? Transmission also are generally several months ahead of VINs. Remember, all the component parts and sub assemblies were completed long before a bike was built from them, and the VIN was applied at completion, not the beginning.

[Taylorfromtucson]

Vin- Wl3908, one cylinder isM 5-12(December 1945 ?) , the tranny I found online right now is 4-6(April 1946).

[Rubone]

The cylinder should be fine, the transmission is likely 'a very high '46 or an early 47.

[Taylorfromtucson]

Out of vin wl1000 to wl6954(per Palmer book), then as a mid year(?) motor I should expect to look for around what month/date code trans? You said trans code would be a little later than vin ? Sorry I didn't answer before...the cases are stanped 46-3403 Where did you find this info, it is great!... I only have the Palmers book and am always looking for more good reads. Thank you so much for the help on this rubone!

[Rubone]

Out of vin wl1000 to wl6954(per Palmer book), then as a mid year(?) motor I should expect to look for around what month/date code trans? You said trans code would be a little later than vin ? Sorry I didn't answer before...the cases are stanped 46-3403 Where did you find this info, it is great!... I only have the Palmers book and am always looking for more good reads. Thank you so much for the help on this rubone!

I said "ahead" not later. The trans will pre-date the VIN.

[Taylorfromtucson]

Ok that makes sense. Is this info in a book somewhere that I can buy??

[Speeding Big Twin]

Your SN and BN sound okay but what do the characters look like? If you’re not sure you could post some partial photos.

What’s the DC on your left case? And if it ends in 5, are the characters spaced or are they close to each other? Photo?
R-H case may or may not have a DC. If it does I’d expect it to be inside the gear compartment but it was often lost when the hole for the generator was machined.

one cylinder isM 5-12(December 1945 ?) , the tranny I found online right now is 4-6(April 1946).

If M is on a cylinder it indicates December casting. But does the plate say 5-12? Or 12-5? A photo in your other thread appears to show 12-5 but I don’t see a letter in that photo.
I can’t read what’s on the plate on your other cylinder but the letter M appears to be nearby?

In your photos it’s hard to read the entire casting numbers on the cylinders. I imagine 120-36 (front) and 120-361 (rear)? Can you confirm please. Thanks.

The trans you found is 4-6? Or do you mean D 6?

Which Palmer book do you have?
Eric

[Architect]

My 1946 WL with a 3000 and up VIN # has a casting mark of F 5, June 1945. But she has a later VIN #. As stated there was time between casting and rolling off the assembly line.

My transmission is 1947, if looking for a "correct" case I would think she needs late 1945 or very early 1946. Late '46 is likely for a 1947 bike.

Have you been inside the transmission yet? Does it have the correct shifting drum for 1946 or the newer style introduced in 1947?

[Taylorfromtucson]

Architect, have yet to find a properly dated tranny case, although I have a servi trans and a wla trans...I am looking(this is all built from swap meet parts). Does the later shifting drum affect anything if used on an earlier shift gate? Speeding twin, yes, the one I found(online, and haven't bought) is d-5. Here are the specifics of the casting marks, I just uncrated it....Front head 5-5 m 120-36 Rear head 12-5 m 120-361 Crankcase j5 Here is photo of vin and crankcase numbers

[Taylorfromtucson]

[Jerry Wieland]

Taylor - Just remember that date codes are only a judgeable attribute on original paint motorcycles. Jerry

[Taylorfromtucson]

I appreciate that info Jerry. I am not looking to have a winners circle 100 point bike. But since you mentioned it, and I get a ton of questions about why I care so much about being "correct"... I want to have as close to a stock bike as possible, or at least as close to what a stock bike or period correct (of that year)bike could be for any given year. I chose the year 1946 because of ease of parts(prewar anything harder to find,) , cost, and styling. I had alot of 1946 year correct parts around. I'm a young guy and I used to have an obsession about WW2 fighter planes that started in elementary school. It transfered over to motorcycles a couple years ago, and I wanted to be able to experience a bike that could have came straight out of that JUST AS IT WAS. That's just how I feel I am better able to connect to that history that I have always been obsessed with. If I could enlist and fly p51s or afford an ME262 on a construction workers salary , I would.

[Taylorfromtucson]

CORRECTION... *straight out of that time JUST AS IT WAS.

[Speeding Big Twin]

Thanks for the photos. I can’t see anything wrong with the visible characters in your SN and they appear consistent with factory stamping for 1946. Here’s an example for comparison of most characters.







I can’t see anything wrong with your left BN and the characters appear consistent with factory stamping for 1946.
Your R-H BN looks normal apart from the fourth character. I don’t know what happened there but I doubt that anybody will be concerned about it.

J and 5 were used twice on Flathead 45ci left cases. I’d expect your J and 5 to be spaced as per this example. The spacing helps indicate casting in October 1945. (For 1945 aluminium DCs the letter I was not skipped.)







Five years later on Flathead 45ci left cases J and 5 were used again but they were normally unspaced (J5) and the 5 indicated 1950 but at this stage it’s unclear whether the J represented October or September. NB: there can be exceptions regarding the spacing and non-spacing of DC characters.








Casting numbers 120-36 (front cylinder) and 120-361 (rear cylinder) are what I’d expect. Your DC plates don’t look like the extra-large types Palmer says were used for 53–73 Flatheads so their smaller size may indicate 1945 as opposed to 1955 or 1965. Therefore the codes suggest casting on December 5, 1945 and December 12, 1945. NB: I cannot yet confirm what Palmer says about when certain sizes of DC plates were used for Flathead cylinders. I’ve done a reasonable amount of research on DC plates for Pan cylinders and Knuckle cylinders but not much on DC plates for Flathead cylinders.

At first you said the trans online was 4-6 but now it’s d-5? I know in aluminium DCs it’s often hard to determine characters because some wear away over time. Here are D 5 and D 6 for comparison.
Eric