TWO-STROKE TUESDAY | WE BUILD A 2008 KTM ELECTRIC START 300XC
Much like the Spartans, there is a small cadre of two-stroke soldiers trying to hold the line at the Battle of Thermopylae. Unfortunately, as most history buffs know, the Spartans were wiped out in that Greek mountain pass back in 480 BC. And, it is likely that the modern two-stroke minions will suffer the same fate. But, not if KTM can help it. Unlike the Big Four, KTM hasn’t quit throwing equipment into the two-stroke versus four-stroke war. And if any bike represents KTM’s commitment (and quirkiness), it is the 2008 KTM 300EXC-W.
Without any focus groups or consumer surveys, KTM threw caution to the wind and built an electric-start two-stroke. You read that right! Some might believe that putting an electric starter on a 300cc two-stroke seems like overkill, but the MXA wrecking crew looks at it as a sign of KTM’s passion for not just the sport, but two-stroke technology.
As motocross racers, we have no real use for the KTM 300EXC-W (E). After all, the “EXC” nomenclature represents KTM’s enduro lineup, while the “W” suffix means that it has a wide-ratio gearbox. The “(E)” stands for electric start. These bikes are in such demand that they sell out quickly. No worries mate! We simply ordered a 300XC cross-country bike and the accessory electric start kit and mated the two together. Why didn’t we use the 250SX motocross model instead? Because the castings for the electric starter are not built into the SX cases, but they come stock on the XC (which is basically an SX with a 300cc engine, larger gas tank and 18-inch rear wheel).
With all of this in mind, here is MXA’s test of the 2008 KTM 300XC (with electric start).
Q: WHY CHOOSE A 2008 KTM 300XC OVER A 2008 250SX MOTOCROSS VERSION?
A: Historically, the MXA wrecking crew has preferred KTM’s 300cc engine (actually 293cc) over its 249cc version. Last year we put a 300 top-end on our 250SX to take advantage of the new SX frame–which wasn’t available on the 300XC in 2007. The upgrade was relatively simple. We had to swap out a couple cylinder studs, cob up a head stay and swap power valve covers. We don’t have to do that in 2008, because the XC gets the fancy chassis.
Q: HOW DOES THE 300XC DIFFER FROM THE 250SX?
A: Let us count the ways:
1. Displacement: The 300XC displaces 293cc from a 72 x 72 mm bore and stroke, while the 250SX punches out 249cc (with a 66.4 x 72mm bore and stroke).
2. Rear wheel: The XC has an 18-inch rear wheel. The SX has a 19.
3. Gas tank: The XC holds 2.9 gallons. The SX holds two gallons.
4. Handlebars: The XC comes with Neken aluminum bars. The SX comes with Renthal FatBars.
5. Transmission: The XC has a semi-wide-ratio, five-speed tranny. The SX has a close-ratio five-speed.
6. Gearing: The XC comes with 13/50 sprockets. The SX comes with 13/48 sprockets. But don’t take the actual numbers seriously. The internal ratios are so different that comparisons can not be made based on sprocket teeth.
7. Ignition: Although both use Kokusan CDI units, the XC has a digital ignition for enduro use, while the SX uses a magneto-style ignition. Additionally, all XC’s have the electric start primary gear already installed.
8. Weight: The 300XC (with electric start) weighs 220 pounds. The bare bones 250SX weighs 210 pounds. The extra weight comes from the battery, electric starter, 18-inch rear wheel, larger gas tank and heavier flywheel.
Q: WHAT DOES THE 2008 300XC ENGINE RUN LIKE?
A: Every MXA test rider is mystified by KTM’s 2008 powerbands. Virtually every bike in their lineup focuses its power from mid-and-up. As a rule, the ‘08 KTM mills are linear and uninspiring down low and then come to life as the rpm increase. We expected the 300XC to be different. By all accounts, its 5.6mm larger piston should have been torquey, chunky and grunty off the bottom–and perhaps a little flat on top. Not so. It was lazy down low and a rocketship from the midrange on up.
Although the ‘08 KTM 300XC is easy to ride, which makes it easier to go fast on, it is a far cry from what we expected from a big-bore 250.
Q: IS THERE A QUICK FIX FOR THE MID-AND-UP POWERBAND?
A: Yes. Since we were only interested in using the 300XC for motocross, which is not what it was designed for, we had no need for the linear low-end power. Additionally, the wide-ratio gearbox, which KTM euphemistically calls a “semi-close-ratio” gearbox, wasn’t helping matters in the tight twisties of a motocross track.
Our quick fix was to gear it down. We put a 51-tooth sprocket on the back. This tightened up the gaps and made it easier to use the late-hitting midrange. As an added boost, we changed to the softer power valve spring to allow the power valve flapper to open less abruptly.
Q: WAS THE 300XS FASTER THAN THE 250SX?
A: Yes. Once we profiled the powerbands, the 300XC was not only faster but torquier than the 250SX.
Q: HOW DID THE ELECTRIC STARTER WORK?
A: The MXA wrecking crew likes to think of itself as being made up of “manly men,” but we loved the “girly” electric starter. It’s not that we couldn’t live without it, but for less than ten pounds of weight it made life so much simpler. While trail riding, it could get riders out of mud bogs, ditches and log jams without having to teeter precariously to use the kickstarter. For motocross, it doesn’t have as many charms, but it’s still cool to never have to lift your leg up on the starting line.
Q: WHERE IS THE BATTERY?
A: In the airbox.
Q: HOW MUCH DOES THE ACCESSORY STARTER KIT COST?
A: According to KTM, the retail price of the two-stroke electric starter kit is under $350. It will bolt on the new-generation XC and EXC two-stroke engines.
Q: HOW DOES THE 2008 KTM 300XC HANDLE?
A: We loved the way the 300XC handled. In fact, we loved it more than the handling of the 250SX, 250SXF or 450SXF. That’s strange, because it has the same dimensions as its motocross brethren. But what the motocross bikes don’t have is suspension that is tuned to work with the chassis. The 300XC suspension is perfect for the KTM geometry. Stuff that we couldn’t do easily on an SXF, we did without breaking a sweat on the XC. There is one giant caveat, though: the forks and shock are too soft for most jump-filled motocross tracks. But it is that softness that lets the bike rail through berms, turn tight inside lines and feel stable through the rough. No wonder KTM owns the enduro and cross-country world. This bike is great in its element.
We thought that motocross wouldn’t be its element, and, as a precaution, we brought the suspension from our 250SX with us every time we raced the 300XC. Shockingly, we were only forced to use it at tracks that were more Supercross than motocross (or when Pros raced the bike). It was too soft, but the softness proved the real capabilities of the KTM chassis.
Q: WHAT WAS OUR BEST FORK SETTING?
A: For hardcore racing we recommend this fork setup:
Spring rate: 0.44 kg/mm (0.46 optional)
Oil height: 370cc
Compression: 20 clicks out
Rebound: 21 clicks out
Fork leg height: 5mm up
Notes: If you want to use the 300XC for motocross exclusively, switch to 0.46 kg/mm fork springs.
Q: WHAT WAS OUR BEST SHOCK SETTING?
A: For hardcore racing we recommend this shock setup:
Spring rate: 6.6 kg/mm
Race sag: 105mm
Hi-compression: 1 turn out
Lo-compression: 15 clicks
Rebound: 24 clicks
Notes: We liked the overall feel of the shock. There were big hits, whoops and square-edge bumps that could over-stress the 6.6 spring rate, but most of the time the rear suspension worked very well.
Q: WHAT ABOUT THE JETTING?
A: Other than making the occasional air screw adjustment, the MXA test crew had no problems with the KTM 300EX’s stock jetting. Here are the stock 300EX jetting specs:
Main Jet: 165
Pilot Jet: 35
Clip: 4th from top
Air screw: 1-1/2 turn out
Note: We tried to keep the engine on the edge of lean to help the laggardly low-end feel crisper.
Q: WHAT ABOUT THE GEARING?
A: We added a tooth to the rear mostly out of frustration with the metronome nature of the low-to-mid power output and the wide gear ratios. We were looking for more life off the bottom.
Q: WHAT ABOUT THE BRAKES?
A: Don’t even think that your Honda, Yamaha, Kawasaki or Suzuki has powerful brakes. KTM owns the braking world. The KTM’s front brake is awesome.
Q: WHAT DID WE HATE?
A: The hate list:
(1) Gas cap. Last year’s gas cap leaked. This year’s gas cap is impossible to get off (thanks to its convoluted push-button lock). Our solution? We run last year’s gas cap and put an O-ring under it to stop the leak.
(2) Side panels. We’ve given up on trying to convince KTM to put true-to-life side panels on their bikes. Now, we’d like to convince them to put on number plate backgrounds that use the airbox area to enable numbers to fit. That is what every aftermarket graphics company already does.
(3) Lifting. We don’t like having to lift the bike by holding onto the rear fender. The fender and our fingers might be strong enough, but it’s wrong (in a Nixonian way).
(4) Silencer. Someday archaeologist will be excavating old motocross tracks and they will find all the muffler nuts that have fallen off KTM two-strokes. The large star-shaped nut holds the end cap on. Correction, the large star-shaped nut does not hold the end cap on.
(5) Sprocket bolts. KTM holds its rear sprocket on with Torx bolts. Why? Weren’t there any Whitworth bolts available?
(6) Gearing. We added a tooth to the rear sprocket to give the rather flat powerband more punch out of turns.
(7) Gas tank. We have no use for almost 3 gallons of gas, but we never noticed the big gas tank. It’s very slim, well tucked-in and most of the gas is located low in the frame (especially when you are only putting in one gallon).
(8) Tires. We can live with the Bridgestone M59 front, but the 402 tire had to go. The 18-inch rear wheel delivered a nice absorbent ride. The bike felt plusher than with a comparable 19-inch wheel.
Q: WHAT DID WE LIKE?
A: The like list:
(1) Brakes. The front is the best in the biz–260mm of pucker power!
(2) Swingarm. Take a close look at it. It is cast out of one piece of aluminum.
(3) Triple clamps. The CNC-machined KTM clamps have four-way adjustable bar mounts and adjustable offset (20mm or 18mm).
(4) Hydraulic clutch. The feel takes a little while to get used to, but it is self adjusting and consistent.
(5) Weight. Even with an electric starter, this bike feels lighter than any four-stroke (250 or 450) on the track.
(6) Air box. No tools needed, but be careful about getting the filter cage seated into the back edge of the intake tract.
Q: WHAT DO WE REALLY THINK?
A: We think that if we weren’t so single-mindedly driven to race motocross that we would buy a 2008 KTM 300XC (with an electric starter kit) and use it for trail riding, cross-country races, enduros and local motos. This is a very, very good machine.
You can read the complete history of the ktm 300xc here.