What is the difference between KZ650B2 and KZ650B2A?

It says KZ650B on frame label. I assume B2 is for 78 (this is what I am finding everywhere)
But online store selectors keep asking if it's B2 or B2A. I "suspect" it's color, but not sure.

Mine is black which probably not original.

The only real difference is the carbs. The B2 has 24mm Mikuni carbs. The B2A has 22mm Mikuni carbs. I'm pretty sure the reason was a California emissions thing. Ed

“A” stands for California than?

I believe it just indicates a mid-model-year change. They changed something on the B2 during production and called the revised model the B2A.

I have two different KZ650 manuals. One lists the B2 and one lists the B2A. I can't really tell what's different (the specs for the B2 are oddly omitted), but I can confirm that the FSM lists the same difference in carbs that 650ed mentioned. And for random trivia, based on the back covers it looks like the B2 started at frame number 027501, the B2A started at 32200, and the B3 started at 46201.

Ok, meet the unicorn

3/78 build date. Title says 78
And here is serial starting with 520...

At CycleChaos.com the 1978 KZ650-B2 has two different beginning frame numbers: one of them is KZ6500-508016. I don't know if that would make yours a B2A. Out-of-sequence numbers seem to be denoted by (L), but I don't know what that means.

By katit: “A” stands for California then?

Kawasaki probably added the A to distinguish it from the B2 but not necessarily to denote it as a California model.
Kind of related. This may not apply to your 650B, but in the parts diagrams CA is used to indicate parts found on California models & CN is used for Canadian models. I see this most often in regards to the air cleaner & carburetor parts diagrams. Plus US is used to note parts found only on USA models, such as the accelerator pump on my 81 KZ650-CSR >> Canadian 650s wouldn't have had the AP. I don't know if Kawasaki did this with the 70s models, but it seems pretty common with later KZs.

martin_csr wrote: At CycleChaos.com the 1978 KZ650-B2 has two different beginning frame numbers: one of them is KZ6500-508016. I don't know if that would make yours a B2A. Out-of-sequence numbers seem to be denoted by (L), but I don't know what that means.

By katit: “A” stands for California then?

Kawasaki probably added the A to distinguish it from the B2 but not necessarily to denote it as a California model.
Kind of related. This may not apply to your 650B, but in the parts diagrams CA is used to indicate parts found on California models & CN is used for Canadian models. I see this most often in regards to the air cleaner & carburetor parts diagrams. Plus US is used to note parts found only on USA models, such as the accelerator pump on my 81 KZ650-CSR >> Canadian 650s wouldn't have had the AP. I don't know if Kawasaki did this with the 70s models, but it seems pretty common with later KZs.

The frame numbers at Cycle Chaos that are preceded by (L) are the Lincoln, Nebraska numbers.

So it's a mistery and I will never know if I have B2 or B2A looks like

Change of topic - noticed on picture that label is slightly peeling. Is there any way to remove it and re-attach later? Plan to re-paint frame and that spot won't look good..

The frame number you posted would indicate the bike is a B2A built in the US. To the best of my knowledge it was offered in ebony. I have attached a table I created in the past with frame and engine numbers I could find. Not saying it is 100% correct but what I could find and make sense of .

gd4now wrote: The frame number you posted would indicate the bike is a B2A built in the US. To the best of my knowledge it was offered in ebony. I have attached a table I created in the past with frame and engine numbers I could find. Not saying it is 100% correct but what I could find and make sense of .

According to your table yes, it does look like B2A.
How did you figure out it's "ebony"? Any pictures of this color scheme?
Another question, is there any difference between units built in US and Japan?

The "KZ650 B2" was made before January 1st 1978. It will still have the OFF/ON headlight switch, and richer jetting in carbs.

As of January 1st, 1978 by federal law motorcycle headlights had to be on at all times, and stricter emissions standards.

The "KZ650 B2A" was made after January 1st, 1978. No more OFF/ON headlight switch, and super lean carbs.

The B2A version took forever to warm up due to those lean carbs!!!!! Customers hated the long warm up time before they ran right.

Quickest way to tell them apart is just look for the OFF/ON headlight switch!!!

Same applies to the KZ1000 A2 and the KZ1000 A2A,

Dr. Gamma wrote: The "KZ650 B2" was made before January 1st 1978. It will still have the OFF/ON headlight switch, and richer jetting in carbs.

As of January 1st, 1978 by federal law motorcycle headlights had to be on at all times, and stricter emissions standards.

The "KZ650 B2A" was made after January 1st, 1978. No more OFF/ON headlight switch, and super lean carbs.

The B2A version took forever to warm up due to those lean carbs!!!!! Customers hated the long warm up time before they ran right.

Now this is great info!! Thank you. So, mine is definitely B2A than. I am going to dig into carbs soon, will see what they look like (and what jets). I plan to run stock airbox and 4->exhaust as this is what I have..