There are two sizes of handlebars which pretty much cover every dirt bike since the beginning of time:
- 7/8”: AKA two piece bars, 22.2mm bars, bars with a cross brace. This size was traditionally the standard for all motocross bikes as the technology for tapered bars was not around until the mid to late 90’s and when it was introduced they were quite expensive.
- Fat bars: AKA tapered bars, 28mm bars, 1 1/8”, oversized bars. Are the newer technology featuring a handlebar without a cross brace to allow for some flex and more rider comfort, but to increase the strength the bars taper up to be thicker at the clamping point.
- Twin walls: Just to make it tricky a third style of bar was introduced being a twin wall handlebar, the simplest way to describe these are a fat bar with a cross brace which are still 1 1/8” at the clamping point.
The crossbar was there for added strength of the handlebars but as technology became better the opinion was the crossbar made for a very rigid feel and the rider would fatigue quicker.
Basically there are just two types of handlebars, the 7/8" bars (identified by their cross brace across the middle of the bars) and 1 1/8" bars also called fatbars or tapered bars (a fatter bar through the length of the bar with no cross brace across the middle).
Either bars can be fitted to your bike, the only issue is the mounts that the bars sit in as each type of bar has a different thickness at this point.
If you have 7/8" bars on your bike right now the mounts you have will fit this type/thickness of bar. If you want 1 1/8" (fat or tapered bars) you will need to purchase a bar mount that converts the mount you have to suit or replace the mounts you have to suit your new bars. The same rules apply if you have 1 1/18" bars and want to fit 7/8" bars to the bike.
The only exception to this rule is the Twin Wall bar which is a fat bar with a cross brace which is designed to offer premium strength.
For any dirt bike 125cc and above the standard handlebar width is approximately 800mm, if a set of bars has the word Mini in the title, it has been designed to fit 65cc, 85cc, 100cc and 150cc 4 strokes (mini race bikes). These have an overall bar width of around 775mm.
Some handlebars come with markings on the ends to allow riders to trim some width off the ends of the handlebars to suit different riding styles.
Providing you have the matching bar clamp sizing you can put wide bars on a mini bike and also mini bars on a full sized bike if you are desperate to go for a ride and can't find the bars you would normally run. Just bear in mind the geometry and ergonomics of the bike will be slightly off and may feel awkward for the rider.