One of the hard things about owning equipment is when it gets old. I always struggle with when an older piece of equipment breaks is trying to decide if I should fix it or scrap. It doesn't matter if it's a lawn mower or a motorcycle. If you are like me you don't like to spend any more money than necessary, but it's also really cool to get a new toy. Personally, I tend to lean toward fixing what I have rather than getting something new. But it all depends on the piece of equipment, how well it's been taken care of and what else is getting ready to break. In most cases the reality is that you are better off fixing and keeping what you have rather than replacing it.
The first question you should ask yourself is "why", why are you thinking of replacing that bike, mower, chainsaw, etc. Is it because it is really old and worn out, or is it simply because it looks old and worn out and you want something shiny? Is something new actually going to be better? Here are some things to keep in mind when making this decision. First off, in most cases when it comes to equipment there is not much difference between a fifteen year old riding mower and new one. The only real difference is how they look. For the most part, most equipment has not undergone any significant change in design or technology in many years. In fact, in my opinion, when it comes to equipment, older is often better. So maybe instead of junking that old mower, consider giving it a tune-up and getting it painted.
When it comes to bikes and ATV's believe it or not you can make much the same argument. Unless, however, you are talking about going from a carbureted machine to fuel injected. But even then the differences are not as huge as you might think. The biggest changes you will see in dirt bikes since the 1990's is the change in suspension and fuel delivery. The last few years have seen some pretty big changes in the dirt bike world with fuel injection becoming more and more popular, new suspension designs and so on. But, again, if you are thinking it's time for a new bike, stop and ask yourself why? If you are happy with the performance of your current machine, but it's looking a little dated my suggestion is to not get rid of it, rather give it a face-lift. With a very small amount of work you can pretty much put any front fender you like on a Japanese bike. I really like the look of the newer YZ front fender. I like it so much I put on an old 1993 Honda XR250l. It looked natural and gave the bike a whole new look. For most Japanese bikes there are lots of relatively in-expensive replacement body parts and graphics kits available. The real trick to saving money on these is buying in the off season (like now) since there are lots of sales and clearance deals available. I am in the process of fixing up a 2002 YZ250f, by buying clearance I was able to get a set of shrouds and a graphics kit for what I would have paid for just the shrouds last summer.
ATV's are not quite as easy to upgrade the look since fenders tend to be very model specific. But, there are ways to restoring faded fenders to make them shiny again, and there are some aftermarket alternatives that are going to be cheaper than OEM if they need to be replaced. Graphics kits and numbers are also a way to go. Keep in mind the vynil used in modern graphics is tough stuff, you would be surprised how much abuse it can take and still look good.
I will admit that there is a time to let it go. Sometimes you can get just too much time on a machine and it has too many problems to make it practical to fix anymore. So when you get to the point where you need to make a decision always try to look at it objectively and honestly. But, if you really want a new bike, mower, chainsaw, etc. then do it and be happy!