I built a '94 kx250 into an enduro mount and it was expensive to get it into anything near the ec250 for off-road work and a couple of things weren't easily dealt with on the kx... (namely fuel tank and the five speed close ratio gearbox)
My KX...
- Laced up an 18" rear rim (gasgas ec comes with 18" rear rim stock) - better flat resistance and tire selection off road with an 18" rim.
- Stock porting was very rough on the kx - sent it to slavens in colorado - absolutely beautiful. Didn't feel the need to do any work on my old gasgas ec300...
- Added ohlins shock to the KX. The EC250 you are looking at has one on it stock. Alloy steel shock body on the ohlins has less fade and requires less maintenance - aluminum bodied kyb on the KX "fouls" the shock fluid faster.
- Fuel tank - very small 2.0 gallon capacity on the KX - added a larger fuel tank - but the perimeter frame plus the small stock tank makes after market tanks stick way up or out to the sides, much moreso than the gasgas - carrying the fuel up higher on the KX makes it feel very heavy when topped off with fuel. The gasgas is designed as an enduro and the perimeter frame accommodates more fuel down low and mass is more centralized. GasGas has enough fuel for me to do 50 miles with the stock tank - the KX didn't...
- I Geared down the KX for the woods but then the five speed close ratio gearbox would run out of steam on fire roads connecting the trails - so guys on KTMs would blow by me when things opened up. GasGas comes with a six speed wide ratio gear box - much better for tight woods/open terrain combination without having to re-gear. Lug the gasgas around the woods and do 75-80 when things open up on the gasgas - not so on the kx...
- I had the front forks revalved by Moose - horrible. The guy put in a single stage stack that was *way* harsh. The WP forks on the gasgas , revalved by LTR, are much better quality than the KYBs on the KX. Although either can do the job.
- I also added a rad-valve for better bottom end and mid on the KX - the gasgas comes with a boyeson rad-valve (reed cage) stock.
- The gasgas comes with a kickstand - although it will quickly auto-retract and auto-amputate any limb you have in the way!
The gasgas is much better suited for off-road work than a KX - depends on what you want to do with the bike... I put thousands of dollars into the KX and at the end of the day I needed a wide ratio tranny to "finish it off" - moose made a kit at one point... I think it was a taller 4-5 gear - But big $$$. It took dramatically less $$$ to get the gasgas into shape - personal preference stuff like suspension valving, bars, etc.
jeff