Well you must know that I am partial to 2 stroke dirt bikes. My personal offroad only bike is a KTM 300 and I chose a TC250 for our flagship. But I also own and LOVE an XR650R and have raced 4 strokes from Mexico to Colorado. We also work on and do lots of performance work to both types of bikes. And we LOVE all dirt bikes and ALL motorcycles for that matter. Here is my short and curt reason I love 2 strokes the most!
So lets start with maintenance. Since that is part of what we do all day every day, it is a big part of how I choose a bike to ride day in and day out. Lots of people say that 2 strokes need more maintenance but that is just wrong no matter how you look at it.
First of all lets talk about oil changes. A modern, high performance 4 stroke requires an oil change every 15 hrs of operation at the very minimum. If you go past this interval you are taking a chance at serious engine damage since a modern bike only holds about 1 quart of oil and it lubricates the transmission, clutch and motor (except Hondas but then you only have about 650 cc's of oil in its motor). To do this service correctly you are buying high end synthetic oil and a filter every time.
Now lets look at 2 strokes. The motor oil in a 2 stroke is mixed with the gas and is effectively changed every time the motor makes a revolution. The transmission oil is the only oil you have to change and since it just runs in the tranny it isn't all that critical. As long as there is good oil in there it is pretty much OK. A modern full size bike holds about 850cc's of tranny oil and there is no filter so its way cheaper to do a normal service on the bike.
Now lets talk about bigger motor maintenance. If you read your owner's manual you will see that if you follow their suggestions you will see that both 4 and 2 strokes require top end replacements more often than you would like. I won't go into details but I can say without a doubt that the parts cost for top end maintenance for a 2 stroke is about 1/3 the price of a 4 stroke. Now people argue that 4 strokes don't require maintenance as often as 2 strokes but that isn't true. That may have been true when the only 4 strokes were the likes of XR's but nowadays 4 stroke bikes need pistons at the same interval or earlier than most 2 strokes.
Now lets talk about the complexity of the job. Even though I make my living working on bikes I honestly believe that most owners could do a top end on a two stoke with a few tools and a manual. I DO NOT believe that is the case with 4 strokes. There is so much more going on with a 4 stroke and so much more could be ruined if you don't know what you are doing. It also costs a lot less to have a shop rebuild a 2 stroke than it does a 4 stroke.
So we have talked about the costs but I think that what really matters in every true motorcyclist's heart is excitement and fun. I have ridden and raced just about every type of bike you can imagine. And while I have never and will never be a professional racer or rider I can say without a doubt that there is NOTHING more exciting or FUN than trying to keep a 2 stroke in the powerband.
I know that there are lots of people being brought up who have never ridden a 2 stroke and I understand that if you want to compete on the national level in motocross or supercross, you have to ride a 4 stroke. But I recommend that everyone at least give an old smoker a try at some point. I honestly believe that they represent the true heart of motorcycling! Either way, GET OUT AND RIDE!!!!!!