This is our final wrap-up on the 2007 KTM 450 SX-F, and we wanted to find out how it held up after 52 hours of riding and racing. I originally chose the 450 SX as my long-term bike because of the innovative electric start and the KTM's mellowness compared to most 450s. Having never taken the time to adapt to the slightly different feel of a KTM MX bike, I also wanted to give it a fair chance to prove its worthiness. I prefer riding 250Fs, but because I was planning to compete in the Vet class at the Loretta Lynn's AMA Amateur National Motocross Championships, I knew I was going to need a 450 to get decent starts.
Overall, I liked the lessons learned with this bike. First, the MX-Tech suspension is well worth the investment. I found the KTM suspension (especially the fork) extremely harsh on the small chop in stock trim. The MX-Tech mods made the bike work really well in most conditions and also worked for a wide range of riders with just minor adjustments to the clickers and preload. The KTM Hard Parts damped bar clamp is very trick, and if you can afford the $299 price tag, I'd recommend them for any KTM. The Sunstar sprockets and EK chain held up extremely well, and I really liked the Bridgestone tires on almost all track conditions. If you're looking for a little more bottom-end snap (more like some of the other 450s), the Dubach Racing aluminum/stainless exhaust is a good choice and held up extremely well although it was a bit loud, especially compared to the stock system. As I noted in the second update (Nov. '07 issue), a larger 48 pilot helped the bike start easier with no negative side effects. Another trick a few of our riders liked was when we removed the head stay (top engine mount). It definitely allowed the bike to work better in sweeping turns.
With small modifications and time spent getting used to the KTM 450 SX, Sean Finley was ready to chase the amateur nationals.
So how did the motor hold up to a full year of abuse? Other than an extremely large ring end gap which was over 2mm, the top end looked incredibly good and was still running strong. It was neither eating oil nor did we feel a loss of power, so we were pretty shocked to find this. We were having starting issues that we attributed to the battery seeming weak. And since the valves checked out OK, we were even more convinced it was the battery. But the ring gap explained it. There was no evidence of the bike sucking dirt as the piston and cylinder, as well as the valves, were all in perfect shape. Maybe we just had a soft ring? In fact, the whole top end looked perfect and was reassembled with only a new set of rings. During the year we never had to adjust the valves, either.
Sean Finley puts his KTM to the test at Loretta Lynn's AMA amateur nationals.
For those of you who are considering making the leap from the Japanese MX weapons to the KTMs, I can tell you that especially for true outdoor tracks, you'll find it worth the jump. The 450 SX-F has a slightly tall feeling but turns incredibly well with or without a good rut or berm. The only place I felt a disadvantage was at the square-edged Glen Helen Raceway track or on hooked-out jumps at speed. The orange bikes are extremely easy to work on because they're just better thought out for basic maintenance (you won't find an easier bike to change the air filter on), and all of the hardware and critical parts hold up better than most. Just a peek at the yearly maintenance and repair costs proves that.
Final Tally
Hours on Bike: 52.0
Modifications: $1059.09
Maintenance and Repairs: $661.72 (not including tires)
Compression ring: $27.67
Oil ring: $27.67
2 O-rings: $3.52 ea.
Head gasket: $24.94
2 oil changes with Maxima Maxum 4 Premium oil: $6.14 per qt
The ring gap was an extreme 2mm. | 
The valves looked great and required no adjustment. | 
We put this piston back in with new rings. |
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