Here's a video I took of mr moving the front sprocket back and forth on the counter shaft with my finger.



There isn't meant to be any travel like that right? It's supposed to be snug? 
In the second half of the video, I pull the sprocket out and do the same. There is no travel.

Does this mean my splines are worn down? 
Is it bad? Do they need attention. My chain is a bit noisy so maybe that is the cause. 

Did a bit of reading and it seems you'd have to crack the engine open and replace that part for a fix which is no easy task.
Probably have to get a shop to do it. I wonder what the cost would be and whether it is worth it. The bike as 80k on it and is a 2000 model.

Here is a pic of the countershaft without the sprocket: 
http://i.imgur.com/WzrvsxO.jpg

And here is a pic of the sprocket. I was reading that after market sprockets can be harder than the originals and if they are harder than the metal in the countershaft, it can wear them so maybe that is what happened.

http://i.imgur.com/1Uj4FP1.jpg 

That play seems excessive.
Possibly some or most of it is in the sprocket itself,and the actual spline is relatively ok.Before i started stripping the engine and paying huge $ i would try a new sprocket.
Farmer Joe's solution is to weld the sprocket to the shaft....rather a crude "fix". 

The picture of the spline w/o the sprocket looked to me like the teeth were badly worn in both height and width.  Bike has 80k miles on it, get a good quality sprocket and weld it on and you should get over 100k miles out of it.

Run it until it spins freely. This is one of those things where there's absolutely no benefit in fixing it before it fails.

damn, so when it's toast, it's toast and there is no point trying to fix it. 
Getting a mechanic to replace the part would be too much money, eh? 
Sounds like cracking open the engine and doing it myself is not really something I can do myself looking at youtube videos and reading tuts.
Don't think I really want to weld it on as I heard that can really wear some other parts as there is no play and I don't know how to weld.

I should say the bike has 80k km not miles. That is about 50k in miles.
I keep forgetting you guys will majority have bikes in miles not km.