45 Years of Four Stroke & Two Stroke Racing
I have been racing over 45 years, raced 4 strokes long before anyone else, in the 60's, Ducati's, BSA's, Triumph's, 1978 CCM's. Then Husabergs, then 98 YZ400, many different 2ST's in between them. Then KTM's since.. Stayed on 4ST KTM's until 08, then got 300XC along with 450 SX. Have ridden many 250SX's, XC's also.
Bottom line, IMHO, for MX the 450 is easier to ride at a fast pace, but not as fast as the 300 which is harder to go that pace, but you can go faster. The 250 may not feel as fast but is faster than both of them as you can use the power better. It revs slower and you can turn it on in the turns much earlier. Stock for stock the 250 has much better power than the 300, it has more low end and revs out further also. The 300 has too much when it hits the midrange, you can't always shift when needed to keep it out of that unmanageable power area. The 250 pulls smoothly through that area allowing you to leave the gas on and go further sooner.
True, the 300 feels very fast and it is much faster than any 450, and if you can short shift it, it will work great. But it is a handful to concentrate on while trying to negotiate anything, turns, jumps or trails. It is fun to have the power of the 300, but it is not needed to ride your best. I have timed many racers from vets to pros and the result is always the same, the 250 2ST is fastest around the course, especially an off road course, no matter how they feel on them. We are talking a normal racer here, 99.9% of us are not Bubba, RC or Reedy. Actually, depending on the track, it may be the same for them also.
The 300 needs some modifications to make it run right, take .020" off the cyl. base and .010" off the head, the compression is low on them. Raise the MJ for your elevation and a needle accordingly and it will run very similar to a 4 st. with much more power,(approx. 60 HP), less weight,( 30 to 40 lbs.), no stalling, quicker starting and better handling. Even doing all this, it still will not be as good as a stock 250, it is too much to handle in many places, even with the mapping switch off. You do need to adapt if coming from a 4ST as they do not
slow down by themselves like a 4ST when letting off the throttle. Which is an advantage in big bumps or whoops as they do not drag themselves down into the holes when slowing down going into turns.
You also need to use a lot of throttle control on the 300 to maintain good traction and contrary to popular belief, the 2 ST goes through muddy conditions much better than a 4ST. Just ride them both in the same muddy condition and you will see, KTM 250 2ST's win almost every tough off road race. Strange, just a few years ago everyone had to adapt to the 4ST from the 2ST.
I have raced my 300 for over 24 months, over 160 moto's/80 races, never lost a start to anything or anyone, most of them on 450's and 15 to 45 years younger than I, except to one guy on a KTM 250 2ST. Never lost a moto to anyone in my class, 20 years less than I, except 1 1st moto to a KTM 250 2ST and never lost an overall. But I do believe I can go faster, easier on the 250 and am looking for a 250 cyl. now to change my 300. I do like riding my 450 esp. when I don't feel 100%, but I do go much faster on the 2ST.
You will have to decide what you like best for your enjoyment, the feel of power, 300 and 450, the ease of going a decent pace, 4ST., or going your fastest, easiest, 250 2ST.
It would be great if you could ride them all back to back at the same course to compare, but I am sure the 250 would be the best, fastest and easiest.
Remember, the 2 ST. requires very little maintenance, rarely ever break, and if they do, you can fix them inexpensively on your lunch break. The 4ST. requires lots of maintenance and WHEN it breaks, you will not be riding for quite a long time while waiting and saving for the repair cost. The 4 ST's have caused the decline in MX as when they break, the racer cannot afford to fix them and does not have the ability to do so themselves. They are more or less throw away race bikes.
Compared to a good 2 stroke that a racer is used to, the 4 stroke is like racing a garbage truck. Also read the Two-Stroke Manifesto feature in November's MXA.
No matter what you decide, make sure it's the best though, KTM !