Does anyone out there know how to tell the year a Honda motorcycle engine was made? I can easily find what the first 5 characters are for with a quick Google search. Example: SC48E-XXXXX seems to be for the 919's. I've seen a few places say the last digit is the year it was made, but I've seen a 919 engine with a "9" for the last digit. I've already called my local dealer and they had no idea. The reason I'm asking is that I'm shopping around for engines and some people out there have no idea what year bike it came out of.
Whoever it was that told you the last digit was the year needs to be beaten with a club studded with nails. They're an idiot. Honda has never done it that way.
The serial number of the engine on Hondas made after the CB model prefix appeared in the 1960s works as follows:
Assuming SC48E-XYYYYYY for a serial:
SC48 = model code, can be as little as two or three characters
E = this serial number is for an engine, there are other parts with unrelated serial numbers on your bike
X = what year or variation of engine, where 1 = first year of bike, 2 = second year, 3 = third year, etc., etc. On some Hondas with a *really* long production run, this may be two or more digits, or it may even have letters (rare).
YYYYYYY = the actual serial number of the engine, what number it was in the production run. This does NOT always match the serial number part of the VIN number or chassis number on a Honda even on brand new showroom bikes.
Honda used to have an identification book they published every so often to help figure out this sort of thing. Each model would be sorted by year, have some basic notes to distinguish the model and list the chassis and engine number ranges. The last full edition that I'm aware of was produced in 2000; even today copies of it go for stupid money.
There was a 2001-2005 model supplemental, but there hasn't been anything since then. Here are some samples for illumination, using our bike's cousin, the last Nighthawk 750. All pictures clickable for higher resolution versions.
As you can see, every year has its own chassis and serial number range. Sometimes there was early production or overlap, so you can have one 'year spec' that actually has a production date that's out of range but the serial numbers will tell the real story. Sometimes there are engine number overruns (but extremely rarely) where the number series runs over to two year specs of bikes. There have also been recalls - there are a bunch of 1984 Nighthawk 700S running around with numbers that are technically out of range for the 84 but aren't in range for the 85 either and that was because the engines were recalled and replaced with bugfix versions or had the cases replaced (defective machining) necessitating a number change in some cases. Some just got 85-spec engines at the Honda dealer, though.