Here are the differences in the 3BN Cylinder head
[image: 1483566896896-dt125rheads-diffrences.jpg]
It'll be marked on the cylinder head.
[image: 1663628447669-874e98a1-e604-4e06-9310-d20f77cae655-image.png]
The 3BN head is interoparable with the 3MB head, but has a combustion ring which is said to adversely affect performance.
Here is a video of the difference between a 4FU cylinder and a Belgarda 3MB00P cylinder.
https://www.youtube.com/watch?v=P8okvTxe-Bs
Here is a 3MB cylinder.
[image: cylinder-1_medium3MB1131100-02_4baa.jpg]
[image: 1663628477295-8e899a28-4514-4881-89ec-bfcc824ade10-image.png]
You'll see the crankcases are stamped 3BN
[image: 1663628512647-b054f520-0af7-4920-948f-cc532b8bbd25-image.png]
For the most part you don't need to worry about it, it'll be rare that you'll find a DTR with a 3BN crank/cylinder and most of them will be 3MB cylinders. But it's just worth bearing in mind.
There are variations in CDIs and Exhausts which affect the performance, but these are less important as there are aftermarket support that recitfies any loss in performance
