During the last 50 hours, the bike spent time in the desert and local mountains, but it racked up hours and miles at the Best in the Desert Nevada 200. Casey Folks and Scot Harden put on an incredible ride with an amazing variety of terrain. Probably the toughest conditions for the engine were the bottomless sandwashes. To help rack up hours, former National dirt tracker John Hateley took it fire-roading. Then some of the lads from work were looking for a mount for the Glen Helen 12-hour endurance race. That was enough time to finish out the 200 hours the bike needed with a little to spare. Unfortunately, the connecting rod bearing (big end) let go eight hours into the event. The engine never stopped running, but it began making ugly sounds and producing less power. At our 24-hour test, Thumper Racing's Gary Hazel said he thought the 525 engine was making too much noise and that the noise was crank related. His diagnosis was the reason I checked out the cam chain. The engine was quieter after the cam-chain replacement, so I thought the engine was fine. The postmortem showed that the bike had not starved for oil, and none of the parts were discolored from overheating. So apparently, the big-end bearing in the connecting rod simply wore out. Even though they were unrelated to the crank, the intake valves were dished, and they needed to be replaced as well. Some parts of the oil pump needed to be replaced, but if we had shut off the engine as soon as it started sounding unhappy, those parts probably wouldn't have been damaged. Before that fatal race, the last 50 hours had been relatively painless.
Despite the connecting rod bearing failure, I feel completely comfortable recommending any of the KTM four-strokes. I believe they are the best four-strokes available for off-road riding. I suspect that my habit of attempting gigantic sand hills over and over again may have been partially responsible for the big-end failure. I don't know that 525s are supposed to get twisted that hard and long. The rest of the engine internals look ready for another 200 hours. I'd love to have the bike back for another 200, and I'm not the only one. Several of the riders who rode the bike during the Dirt Rider 24-hour test asked about buying it, even after they learned it broke! The bike was completely comfortable for me. Since I was trying to get hours on the 525, I haven't ridden off-road much on any other bike in over a year, but now that the test is over, I've had to go trail riding with other bikes. It has been a little frustrating to ride bikes that weren't set up for me and didn't work as well as the 525.
Running TallyHours on Bike: 200-plus
Modifications: $299.99 ($2406.78 total for 200 hours)
Maintenance and Repairs: $871.11 ($1907.38 total for 200 hours) (not including tires)
Rocky Mountain ATV Primary Drive o-ring chain: $42.68
Rocky Mountain ATV Primary Drive countershaft sprocket: $7.99
Rocky Mountain ATV Primary Drive steel rear sprocket: $18.99
Rear brake master cylinder: $149.79
Crankshaft assembly: $473.86
2 Intake valves: $24.89 ea.
3 K&N oil filters: $6.14 ea.
Nine oil changes with Maxima Maxum4 Premium oil: $6.14 qt.
Dunlop D756 rear tire: $100.11
Dunlop D742 front tire: $95.23
Maxxis SI tires (2 sets): $70, front; $82.12, rear
Bridgestone M202 rear Tire: $85.69