Four-strokes are the future, and they are absorbing R&D budgets, headline space and slots on the starting line of every type of dirt bike competition. KTM is a perfect example of the trend. In 1999, you had to have a connection at a West Coast KTM dealer to get a 300 two-stroke. In 2001, a year after KTM introduced its new four-strokes, the Austrian company offered a rebate on the 300! Mike Lafferty won the 2002 National Enduro title on a four-stroke 400 E/XC, and that is the first time a four-stroke won since before a two-stroke won in the 1960s! Also note that only two brands attended our extravagant test with off-road two-strokes. The others either couldn’t attend (TM, for example), don’t import them or don’t even make them. Every brand we invited had a 400/450 four-stroke of somewhat modern design. Granted, the rebirth of four-strokes and decline of two-strokes has as much to do with government intervention as it does with changing preferences of the buying public.The KTM and Gas Gas two-strokes are highly comparable and well-equipped for their intended use. Legally speaking, they fall into the same basket as well. All are closed-course-competition motorcycles. The same is certainly not true of the four-strokes. Legally and in concept and performance, this group of 400/450 thumpers is aimed at different targets. All are considered off-road bikes by riders, if not by various government agencies. However, there are two standards that apply. The federal standard says all off-road bikes intended for use on public lands need a spark arrestor and must be less than 82 decibels. The sound test is administered with the meter 50 feet from the machine while it’s under a heavy acceleration load at wide-open throttle. The Gas Gas FSE-450 has not been turned over to an independent testing lab at this point, so it is still considered closed-course-competition only. Gas Gas said the bike should be homologated by April, and the rest of the four-strokes claim to meet this standard.California just began enforcing a 96-decibel sound level measured at half of peak rpm, with a meter 20 inches from the end of the exhaust. Michigan has a similarly strict sound test. In addition, California requires off-road bikes to meet the same tailpipe emissions standards as street bikes! Honda’s XR400R and all of KTM’s off-road four-strokes meet the smog and sound restrictions for California. The rest are sold as competition machines. In California, they are registered with a red sticker that allows them to be transported on public roads and used in competition. Some riding areas also allow red-sticker bikes during the months when smog is not an issue–usually October to May.Originally, we intended to test every bike totally stock, but frankly, the performance of the Yamaha WR models was so lackluster we decided to allow mods like jetting and removing airbox restrictors and tailpipe baffles as long as the bikes would pass a sound test. Technically, that made these bikes closed-course-competition bikes–ok on our 12.4-mile closed loop. The weather at Glen Helen Raceway Park was perfect for sunbathing or riding with vented gear, but no rain had fallen in SoCal for more than a month. That was great for the supercross season but made for dusty, slippery conditions for the test. Our course was tighter and slower than ever with very challenging climbs and descents.With 11 bikes slated for the test, we couldn’t go crazy with test riders, so six were chosen to ride all the bikes. The fast guys were Elmer Symons (South African off-road champ), Tom Carson (former GNCC Vet A national champ), our own ISDE hopeful/off-road expert Jason Webb and motocross and grand prix pro Kris Keefer. Representing the vast majority of the human race were our B/intermediate off-road/expert trail riders Karel Kramer and Ed Tripp. Eight-time national enduro champ Dick Burleson, fresh out of the body shop, was on hand in an advisory capacity only.Our test ran a straight 25 hours, since we needed an hour off at 5 p.m. for Baja Designs to work its magic on the lights. As usual, our desert-dwelling, hard-core-maniac trail-riding buddies, known as the Conga Line, were back to take the graveyard shift from 1 a.m. to 7 a.m. The Conga Line is made up of just regular-guy trail devotees with a real-world outlook on machinery. Where applicable, we included their opinions on the machines.Without further ado, let’s see how the competitors stacked up. Click on the images and bike names below to read the individual bike tests.