What that tach shows is normal. From 6,500RPM to 10,500RPM is the power band and the red line is at 10,500RPM.

You could modify the engine (better connecting rods for an example) and increase the red line. My brother had a 1972 CB750 that we shifted at 12,000RPM, when the tach showed red line at 10,500 and the highest reading was 11,500RPM. In other words we were shifting off the tach.
That engine was modified exceptfor theconnecting rods and they stretched and broke sending a piston into the head and whipping the broken rod like a hot knife through butter cutting a nice slot in the engine cases.

Without the proper mods the valves begin to float and the is a lose of power. To keep the engine in the proper power range when racing, you would keep the tach in the lower red area (power band) and shift before you get into the big red area. In the big red area things can fly apart.

 

Let's just get some clarity here
I've attached a pic of a 93 Tacho, which has exactly the same face as the 90 model in my bike.
There's no evidence of a red line before 10500RPM.
Your picture (which I've photoshopped) doesn't give me a clear enough image to work from, as it was taken in the dark. Can you take one in the light ?
The earlier models 87 and 88 had figures in RED with a slightly different colour layout. but I can't see one of those having been fitted as the drive mechanisms differ between the 90 and 93, even the housings are different, so can't see it being that.
Give me the engine and frame numbers, and maybe I can be of more assistance......

 

I would call it quality of production, you can see that the red line really starts at 105000rpm, it is more bright at 6500rpm because:

The bubl is misplaced in the back
or it is one defective unit in 10000,the printing was off.

Mine is a 88 with red numbers and i don,t have this neither.

 

Shadow, just so you know, my '87 tach is the same as the '90. It shows redline clearly at 10,500. Nothing at 6,500.

 

frame number-sc242601545
engine number-1601744
engine type-sc 09 E

 

Sawubona Mfowethu !
In case you've forgotten your Zulu - Good day brother !
The E in your engine number is important - E for Economy, I think,reduced HP from 125 + to about 100 HP. Mine was the same, but my tacho has no red before 10500RPM as stated earlier. I think once I get my KPH unit I can send you a tacho... (from a 93 - will fit) There are a few posts from earlier this year dealing with 'fixing' it, but the short answer is to remove the inlet boots between your carbs and engine - If they are original they will have rubber 'ridges' which restrict the fuel and air mix into your carbs. Either grind the ridge away, or buy replacement boots from someone like www.mrcycles.com in the US or www.davidsilverspares.co.uk in the UK, or check e-bay for used ones from a breaker.
Best I can do from here..........hope it helps

Griffin - thanks and also for info - the 93 gauge cluster wont fit the 89-92 models, they are completely different. I tried ! The speedo has a different drive arrangement, and the rear casing is different. Even the mounting tabs don't work. I can't say if the 87/88 are different again - maybe if someone takes a pic of the back of a set of 87 clocks I coud tell you....