KTM 525 MXC Desert Racing

2005 KTM 525 MXC #3 Dirt Bike – Dirt Rider Magazine

Tuesday, February 24, 2009

It all started as I readied the KTM 525 MXC for another trip to Baja. Publisher Sean Finley was borrowing it, and I naturally wanted the big Katoom to make a good impression. I adjusted the valves, put on Maxxis Desert IT tires, changed the oil and filters, and checked the bike over. Since the chain and sprockets were toast, I mounted up a Primary Drive set. The problem is the stock gearing is 14/48 and the sprockets I had were 13/50.

That is a huge gearing change and one I feared would be too low for Mexico. Finally, even though the clutch was acting fine, I decided it needed a fresh one after 100 hours! I finished up the bike at midnight, so I didn’t ride or start it.

Stuff happened, and the Dez-illac remained parked until most of the folks on the ride had left. KTM four-strokes have eight metal plates in the clutch, and four are 1.0mm and four are 1.4mm. Apparently, the set didn’t have enough of the thicker plates. The bike wouldn’t move. With no other option available, Jimmy “Rig It” Lewis cut one metal plate into four sections.

He stacked two sections on opposite sides of the clutch and bolted everything back together. That made the master cylinder low. There was no mineral oil available, so the master cylinder was filled with cooking oil. The hack job lasted the two-day ride with minimal problems, and I got the bike back with a note on the tank alerting me to replace the cut-up clutch plate and to check the fluid in the master cylinder. I checked.

It had fluid, so I replaced all the clutch plates. To avoid experiencing a similar problem, I got KTM’s new prepacked clutch kit, which has the fiber and metal plates packed with new clutch springs. The kit ensures you get the correct parts. Then in the middle of nowhere, the clutch lever went limp. When I tried to bleed the system, the oil coming out was foamy.

KTM 525 MXC Desert Racing
KTM 525 MXC Desert Racing

I limped the bike in, using water in the master cylinder. I suspected a bad master cylinder, so I replaced it and bled the system with ATF so I could get fluid in a pinch if I had further problems. Almost 20 miles into the next ride, the lever went limp and again, the fluid was foamy when I tried to bleed the system.

KTM’s Tom Moen claimed the fluid should only foam when the slave cylinder’s bore wears and the piston starts to spin in the bore. The cooking oil in the system must not have had enough lubricating ability when the engine was hot, and the bore was worn. A new slave cylinder was the cure.

The sad fact is that the list of replacement parts adds up to a big number, but none of the parts would have been necessary if I had just left the clutch alone at 100 hours, got the prepackaged clutch kit the first time or even changed only the friction plates.A cracked left-side footpeg mount was welded and the clutch drama solved just in time for the 525 to run alongside our 24-Hour test candidates at Hungry Valley. A fall bent the muffler and subframe a bit, but both straightened out easily.With just an oil change, a new Maxxis SI rear tire and an air filter, the 525 completed the annual Soboba Invitational trail ride.

It was a super-dusty ride for a change, so another filter and a Maxxis SI front tire were in order before heading up to the Quicksilver Enduro to shoot photos. I was glad of the fresh tires when it snowed 6 inches during the night before the event!The Dicks Racing suspension, Factory Effex graphics and even the Factory 909 grips I installed at 50 hours are still going strong.

Also, the budget-priced Rocky Mountain ATV chain and sprockets still look pretty good.The stock muffler needs to be repacked. As soon as that is taken care of, it will be a matter of finding the time to accumulate the last 50 hours before a teardown. Running Tally

KTM 525 MXC Desert Racing
KTM 525 MXC Desert Racing
KTM 525 MXC Desert Racing
KTM 525 MXC Desert Racing

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