Project KTM 525 EXC: Introduction

May. 01, 2003 By Eric Tabb

We have some new competition in the barn at this month. Our WR450 project bike was beginning to get a little lonely so we bought ourselves a 2003 KTM 525EXC project bike to go alongside the old Yamaha.

Follow along month by month as we dig into this beast! On the left - topics will be listed as we go along. Click on any topic or month to follow along. Pending, scheduled, or tentative items are "grayed out", as they become available the text will become either black or white.

 Playing Hard-To-Get

The big KTMs are pretty tough to come by due to the high demand, which meant we had to do some searching to find one. After a few emails from dealers all around the US we ended up finding a bike close to home. While we didn't take the best deal money-wise, we went with Z Racing in Southern California because they have been a KTM dealer for over 20 years and provide excellent service. They throw in suspension set-up and will continue to work with you for basic bike set-up.

 The Bike

The KTM 525EXC is not a beginners bike, but to the experienced rider it is a very smooth and controllable motorcycle that can handle just about any situation you can put it in. The EXC version of the 525 means it is set up for enduro and cross country. KTM provides a wide-ratio transmission with a low first gear and a blistering fast top 6th gear. The suspension is tuned for general off-road riding, so back flippers and building jumpers need not apply. The fuel tank this year is rather small, at about 2.1 gallons, but gives the bike a small, light and flickable feel. Rounding out the EXC package is the addition of a headlight, tail light and electronic odometer.


Before even thinking of taking the bike out for a high-desert break-in ride some adjustments were necessary. The stock jetting on the 525EXC is very lean in order to pass the smog requirements for California. Since our break-in ride would take place between 3000 and 5000 feet we opted to richen the pilot jet from the stock 42 to a 50. This richens up the throttle settings in the lower ranges so the bike gets more fuel and runs cooler. The needle position and stock 178 main jet were left in place due to higher altitude.

The next adjustment was to re-route the crankcase breather hose. Stock the breather hose comes out of the right front case just behind the headpipes. It runs up under the tank and connects to the carb on the right side. The breather hose is supposed to route crank case gases out of the case and back into the carb to be burned. The problem is that if you lay the bike on its side, or get it upside down, oil can flow up the breather and into the carb. When this happens you can either foul a plug or get oil trapped in the main jet, the latter of which I experienced on my old 95 KTM LC4 400 resulting in idle mode only.

While there are many ways to re-route the hose the easiest we found was just to flip the hose over, connecting the original carb end to the crank case. Then just run the hose along the underside of the headpipe and out the back with the carb-vent hoses. This puts the hose in contact with the lower headpipe in a couple spots, but so far we haven't experienced any issues. To plug the hole on the carb pick up a 3/8" vacuum plug from any autoparts store. It is a good idea to also add a little RTV sealant to the plug and a zip tie just in case you get a backfire in the carb.

 Break In

Once the jetting and breather hose were taken care of we headed out to the Southern California desert for a break-in ride. A stab at the electric start button and the motor came alive for its first ride. The first thing I noticed was this bike has very smooth power. I expected the low end to be somewhat abrupt, especially with the EXCs low first gear. What I found out was that the bike has a really mellow bottom end power that allowed the bike to feel very planted and controlled, even when coming out of turns. Coming off a KTM 300EXC I was surprised at how easy the 525 was to maneuver around at low speeds. The new for 03 tank made the bike feel more like a 250 than a 525 when riding aggressively. Since this was the first ride we kept it easy on the throttle.

After getting the bike home and cleaned up we adjusted the valves and did the first oil change. The manual recommends you do this after the first 3.5 hours so we made sure to follow the directions. While doing the maintenance we decided to change the jetting for more snap and went with a 48 pilot, 4th clip on the needle and stock main. We will do some articles on how to adjust the valves, how to do an oil change and how to change the jetting in the near future. For now just make sure you use high quality tools to remove the 8mm Allen drain plug and the 13mm side bolt that holds the screen in. I think KTM uses some space age cement to hold these bolts in place, because they are a real pain to remove!

 Second Ride Thoughts

The following weekend we were right back out ready to test the bike on our favorite top-secret desert loop. This loop has it all, starting with some fast fire roads moving into tight rocky and sandy canyons, then into deep sandwashes followed by a monster downhill and finally finishing up with one of those fast as you want to go 10 mile valley crossings. Since the KTM was now somewhat broken in we definitely got on the gas a little more. Remember when I said the low end was mellow? In the tight rocky sandwashes the bike ripped right through to my surprise. The stock suspension was very plush and soaked the rocks right up with no complaints. Compared to my 300 the 525 was surprisingly nimble in the tight nasty sections. I give the credit to the smooth low end, great ergos and plush suspension.

Anytime the trail opens up and you twist the throttle, you better hope there are no bugs around because you will get a mouthful from smiling so much! The midrange power on this bike is simply awesome, loads of arm-pulling torque that just continues to build into a very strong top-end. This bikes power just makes you grin. I found myself constantly rolling on the throttle over little bumps or downhills just to get that feeling of controlled power wheelies. After coming down a monster downhill I turned around just in time to see my buddy lock up his front tire, go over the bars and get mowed down by his 360. Since I was on the 525 the only politically correct thing to do was to blast back up the massive hill and laugh at my buddy as I passed him by. I just left the bike in second gear and it chugged up the hill with the front tire hovering just above the trail, now that's what riding is all about!

With the bike now safely back in the ORC barn we are making our list of what to do to our project bike next. We already added a bunch of protective items which will be reviewed soon. Suspension tuning and jetting are going to be high priorities to make the bike the best it can be. Z Racing is going to help us with the suspension, while a not-yet famous jetting expert is going to be assisting us in getting the carb dialed in. Also on the way from CycleZone KTM in Kansas is a dualsport kit, not just any kit but a factory KTM kit! A larger tank is going is also going to be needed for long desert or dualsport rides.

If you have any ideas or suggestions, or if you are interested in becoming a sponsor for our KTM 525EXC project bike drop us a line.

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