What do you think is more reliable a 250 mojave or a 300ex?

 

With proper maintenance and not too much abuse, any 4 stroke quad will last a long, long time.
Of course you are going to hear both sides on this. Everyone has had some trouble at some time or another-if not it's coming-it's just the nature of mechanical things. All parts wear out eventually.
So to say that one is more reliable than the other would take 2 bikes being driven exactly the same, the same terrain, same maint, etc...

 

mordr....not true....you don't need 2 bikes driven exactly the same to determine which is more reliable....2 individual bikes, yes, but a model, no....i will guarantee you that there is a difference in the reliability of the 2 bikes mentioned...i don't know which one is more reliable, but there is definitely a difference....probability, law of averages, call it what you want....there is no way that different manufacturers have the exact same reliability....some brands are more reliable than others...i keep hearing from one of the brand loyal group that as long as you keep up regular maintenance their quads give no problems...some brands require less, some models are just rock solid...i won't get into different brands, but everyone knows that some are more reliable, most will admit it, and some just will never admit it.

 

I have owned a few 250x (the predecessor to the 300ex, they use the same frame, plastic, almost every part in the engine). I have friends that have owned 250x's and 300ex's. All of these have been great bikes. All have been ragged hard and still take abuse. I have yet to see a 250x/300ex with internal engine problems other than typical topend rebuild.
I have also owned 2 mojaves and I have a friend that currently owns 2. I have also worked on about three others. They range from 88-98 models. They all have the same problems. The shaft the internal kick start gear sits on wears and the kick starter stops working. The carbs are junk (I absolutely hate CVK Keihin carbs) they are very tempermental. A 89, a 93 and a 97 I worked on had worn out cams. The stators are prone to failure (typical kawasaki). Timing chains stretch under hard abuse and are expensive to replace. They have soft valves and seats and one of their most common problems is the valves pulling through the head. If you ever work on one, they are harder to work on than a Polaris.
The ride is smoother on a mojave, but the 300ex handles better.
The two posts ahead of me are correct when you compare two bikes. I am comparing almost a dozen.
As for the post by Modr, the basic piston, ring, rod combo will have the same longevity on both. It is the other workings that are different.
The Canadian has the right idea about judging a model instead of two bikes. Also I am not loyal to any brand, just look at my sig. I own a Kawasaki Ninja that isn't listed in there. I complain about banshees more than anyone yet, if I came across another one cheap, I would buy it just because they are what I like to ride.
My choice would be the 300ex. I am sure someone has had problems with them, if so they should post them, but I haven't.

 

i own a 97 mojave and have had absolutaly no problems and i ride the hell out of it

my freind has a ex and he is getting rid of it because he has had many problems
he rebuilt the entire thing a year ago and it is now starting to act up again

just my 2 cents
i no this is not the case with all mojaves or exs this is just my experiance
and again i am not trying to favor one or the other
the mojave has way more hop up potential it is harder to find parts but it is just a better high performance quad
dohc 4 valve as compard to a sohc
liquid coolin as compared to air
8 inches of suspension as compared to 6

this is just my openion the ex is still and awsome quad