If you talk to very many off-road motorcycle enthusiasts, you will find a lot of KTM fans, and you will soon discover that many of them consider the KTM 300 to be one of the best, if not THE best all around dirt bike ever produced. Light weight, great chassis, open class but controllable power and torque – it has it all. Ride one and you will at least agree the KTM 300 is an awesome bike that is enormously fun to ride. The motor is amazing, and combined with the excellent KTM chassis and suspension, it is a favorite choice in the off road world.
What is it about the KTM 300XC and 300XCW that make them so popular among long time dirt bikers? The easy answer is that the 250 and 300 KTM’s are essentially the same bike, with 44 extra cubic centimeters of displacement achieved with a 5.6mm larger bore in the 300. The 250 has an over square 66.4mm x 72mm bore and stroke, the 300 has a square 72mm x 72mm bore and stroke. What you get with the KTM300 is a lightweight and nimble 250 2-stroke with an extra dose of grunt. Some long-time KTM300 fans call the 300 a “3-stroke” because it pulls with 4-stroke-ish torque from a 2 stroke motor, and some lovingly call the KTM 300 the “Three-Hunny”.
We are going to begin our project with a KTM 300XCWe (electric start), which I have been riding and racing for a little while to get a good feel for what we can leave alone, and what we can improve. Why the 300XCWe and not the 300XC? I have ridden and raced both, and the XC version is very nice, has a closer ratio tranny, slightly stiffer suspension, and lighter weight (no electric start). However, because of the tranny differences, the XC has a much lower top speed than the XCW, which can make it less versatile if you trail ride in widely varying terrain, and race a lot of different races – GNCC, Enduro, Hare Scrambles, old school fast grass track, etc.
I also have to admit that the XCWe electric start, although not truly necessary on a KTM 300 that typically starts first kick every time, is pretty cool and has its advantages. Once you get used to the magic button and how it can keep you from loosing a position in a race if you stall unexpectedly, the small amount of extra weight, about 9 pounds, can be well worth it. Keep in mind, however, that what we will do to the project 300XCW can also be done to the 300XC, or the 250XCW or 250XC, which are all essentially the same bike.
ADDING GOODIES IN THE EARLY STAGES
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After spending some time on both 300’s (and the 250’s), the first things that needed to be addressed were the tires, the handlebars, and installation of bark busters and a steering damper. The stock Bridgestones actually worked OK when absolutely brand new, but once the sharp edges were gone off the knobs, they were… well, less than OK, and could scare the crap out of me at any moment. I like the Pirelli XC tires for intermediate and varying conditions, and that’s what I put on the 300. Big difference. It is simply amazing what good tires do for a dirt bike.
Bar choice and bar position is critical for me to be able to ride at race pace for hours at a time. If you are shorter or taller than the average guy, the adjustable bar position on KTM’s is a wonderful feature. I’m a smidge over 6 ft tall, so I swapped the bars for some taller, straighter bars, trimmed them slightly shorter, moved them from the stock #2 position to the #4 position (further forward), and installed my bark busters, the very nice KTM version with the cool “U” shaped mount that gives good clearance for your brake and clutch hydraulic lines. I cannot stress strongly enough what the right handlebar set up will do for your riding, and how it will reduce your arm fatigue, arm pump, hand cramping, etc.
SCOTTS DAMPER, BARK BUSTERS, AND NEW BARS
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I installed a steering damper, a must for me. Once you have ridden any length of time with a steering damper, you will understand. It takes away the front end nervousness over nasty ground at speed, and reduces front wheel deflection off roots and rocks. Any good damper is better than no damper, but I prefer the Scott’s damper (made by Ohlins) over the others. I have tried and still try other dampers from GPR, Ohlins, etc, but I always come back to the Scott’s. The Scott’s damper is super adjustable and only dampens away from center, so it does not wear you out fighting the bars back to center like the other popular steering dampers. This is a big plus, and until you have ridden a properly set up Scott’s back to back with the other dampers, it’s difficult to understand the differences and the reduced fatigue afforded by the Scott’s. I know other people swear by GPR or another brand, and we sell those side by side with the Scotts at KTM World, but I prefer the Scott’s, and I have tested them all, over and over again.
Now that I have the tires, bars, barkbusters, and steering damper sorted out, it’s time to work some magic on the suspension. The newest KTM / WP suspension is the best it’s ever been, but it still comes set up oddly for most riders. However, it has the potential to be very, very good.
KTM’s have good suspension, so it may seem like I am nit-picking when I mention the suspension shortcomings in an article that is mostly about making the motor work better, but I know how much better the suspension can be, and what great suspension does for your lap times. The stock suspension is harsh mid stroke, but there is not enough bottoming resistance, so both ends feel a little too stiff and harsh, then you bottom it on the first big water bar or jump. The forks have too much “hack”, and too much defection on roots and rocks. The rear shock is a little better at controlling the hack, but the mid stroke harshness in the shock is felt over anything bigger than small roots and rocks, and if your butt is on the seat, you really feel it. Plus the shock has entirely too much “kick” over small jumps and obstacles. The bike just never feels smooth and planted.
Fortunately, all of these things can be fixed, and the good news is that we are at KTM World! KTM World does more KTM suspension testing and development than all the other suspension shops combined. No other shop can come close to matching the level of time and effort we put into testing and developing KTM suspension. KTM World is located at Highland Park, a very challenging off road riding park, so we are able to make a valving change and go real world test it right then. This is a huge advantage. Suspension testing and development is a daily thing around here, and the result is the best KTM suspension in the country. Like the old saying – “No brag, just fact”.
SHOCK SHAFT WITH BOTH PISTONS AND GREATLY REVISED VALVING, READY TO GO BACK IN THE SHOCK BODY
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So off come the forks and shock, and by the end of the day, I have both ends of the bike revalved, new springs installed, everything set up to our latest specs. The midstroke harshness is now gone, no more hack from the forks, no more kick from the rear, and no more bottoming out over jumps front or rear. The front end deflection is gone, the bike is super plush on the small to medium stuff, and the wheels feel like they are glued to the ground. The front end sticks and turns like magic. The whole bike feels butter smooth and it gives you control and confidence you never had before. I know this article is mostly about the 300 motor, but great suspension is absolutely the best money you will ever spend on your bike, period.
If you do nothing else to your suspension, at least install the correct springs for your weight and height. Correct springs are critical if you want to ride fast. Be aware that those online spring rate calculators are not 100% accurate. They do not take into consideration all factors, one of which is your height. If you doubt this, just set your rear sag, then pretend you are taller and move your weight back 2 or 3 inches and measure the sag again. Plus the new lightweight variable rate springs we stock are also not considered by those online spring rate calculators, but they are awesome for KTM’s linkless rear suspension, and weight up to 1.7 pounds less than the stock WP springs. If you have a KTM, you need to consider one of the new variable rate shock springs.
MAKING POWER
After some time riding with the reworked suspension (what a difference!), I turned to the motor to see how nice I could make it. The KTM 300 is well known for great power over the entire rev range, but the thing that makes most people love the 300 is the low end pull available from right off idle and the linear transition to a strong midrange. There is plenty of top end, but what really makes this motor special is the amazing bottom end torque and strong early midrange. I love a motor with strong and controllable pull off the bottom into an early midrange. It suits my riding style in the woods – keep momentum up, keep the rear wheel hooked up, and you will cut some fast lap times. Having to rev the pee out of a motor while threading it between trees is not what I prefer. I really like the way the first half of the RPM range works on the 300, so that’s what I decided to concentrate on – making the bottom end and midrange even better.
The first approach was how to increase power without doing expensive motor work, so jetting, exhausts, and power valve settings were tested, changed, tested again, changed, tested, changed… well, you get the picture. We did a lot of testing to see what really works.
We tried three different pipes on the dyno, with both the stock silencer and the KTM Hard Parts silencer (built for KTM by FMF), and found the KTM Factory Hard Parts pipe (also by FMF) made the best overall power, even better with the Hard Parts silencer. Slightly less HP right off idle, but then it starts making more, increasing as the RPM’s increased, with a strong midrange, almost 2 HP more, and about 3 HP more on top. It sure feels like it revs out faster too, making the bottom end and midrange feel stronger than the dyno indicated. The stock pipe, which works pretty well, felt a little sluggish in comparison to the Hard Parts pipe. The stock pipe was next best overall, and the FMF Gnarly pipe we tried clipped the top end, gave it a slight midrange burble that was hard to jet out of it, and did not make the expected gains at low RPM’s. What the Gnarly pipe seems to do is smooth out the power and kill the transition to a strong top end pull when the power valve opens, so the motor is very controllable and smooth, but we could not get it to make good HP. If you want power go for the Hard Parts pipe. If the top end rush of the 300 is more than you want, and smooth power with no surprises is your goal, the Gnarly pipe will be the choice. The Gnarly pipe is heavy, heavier than the stock pipe, and a lot heavier than the Hard Parts pipe. It is, however, more dent resistant. The Hard Parts pipe with silencer was right at 3 pounds lighter than the stock pipe – not bad at all.
KTM HARDPARTS PIPE AND SILENCER - BEST CHOICE!
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The 300 comes with three interchangeable power valve springs, but you will need to purchase the little power valve adjusting tool to adjust the spring tension. You will want the tool – the spring choice and spring tension make a big difference in the power delivery. The power valve controls the height of the exhaust port, which controls the “hit” you get as the motor revs through the midrange, transitioning into the top end. The power valve starts to open at 5500 RPM, and the spring choice controls the RPM range that is required to fully open the exhaust power valve. The green spring opens the PV over the range 5500 – 8300 RPM, the yellow spring (installed at the factory) is 5500 to 7800 RPM, and the Red spring is 5500-7300 RPM. You can see that the red spring will make a quick transition to the top end with a lot of hit and more wheel spin. We found the yellow spring worked best in the woods most of the time, the green spring worked best in sloppy slick conditions, and the red spring was best for fast jeep roads, MX, open trail and fast grass track.
Using the power valve adjusting tool allows you to fine tune the spring tension and most people can tell the difference a turn on the adjuster makes. Two turns makes a big difference. Not as much as changing springs, but the cool thing is that the powerband is so adjustable. With three different springs that can be changed in about 2 minutes, and externally adjustable spring tension that takes 2 seconds to change, you can tune the power delivery to exactly what you like for the conditions that day. On top of that, the new KTM ignition has 2 maps, one for traction in loose/muddy conditions when throttle control and wheel spin are a big concern, and another ignition map for best performance when traction is good and you can use the extra snap. The 300XCWe we used for this project has plenty of flywheel weight and a very tractable motor, so after trying both maps a few times, I discovered the performance map worked best unless you were in super slick conditions. On the 300XC, with closer ratio gearing and less flywheel weight, you will find more use for the dual ignition map.
TILTING THE CAMERA DOWN INTO THE AIRBOX GETS US A PIC OF THE POWERNOW WING
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Next is the installation of a PowerNow carb insert and jetting. I have previous experience with the PowerNow, and it’s really just a flat wing that sits horizontally in the intake bell of the carb, but it does work. I did some flow bench testing on this product some time ago, I can tell you that it really does do what the manufacturer claims, which is to reduce air turbulence and increase air velocity, especially at half throttle or less, resulting in better throttle response and better low RPM pull at partial throttle settings. It’s not an amazing difference, but it is definitely a noticeable difference, it’s easy to install, and the cost is more than reasonable for the gains you get. The 300 likes leaner than stock carb settings in the warm Georgia climate, especially if you want a clean crisp pull off the bottom and through the midrange. The bike comes with a #35 pilot jet, and that is as lean as you will find readily available. But that’s OK, the 35 pilot works well in the 300 most of the time. Only a very cold Winter day when the air is oxygen rich will make you consider a larger pilot jet. The #35 pilot stays, but the stock needle is too rich. For warm weather, use the leaner needle supplied with the bike. For our typical Georgia weather, the leaner needle in the second to leanest position (#2 from the top) worked best, but in mid Summer or Mid Winter, this will likely change a bit, and if you are in the Winter up North, you will not be using the leaner needle. After lots more testing, we settled on a #162 main jet. This jetting worked well with the stock pipe and the KTM Hard Parts pipe, the bike had very nice throttle response at lower RPM’s, and had much better pull throughout the rev range. Fuel mileage improved too.
OK, the suspension is working great, the motor runs very well, what’s next? Remember I mentioned earlier that what 300 owners love about the bike is the strong bottom end pull, and we massaged the power with some bolt on goodies and proper jetting, but I wanted more. Time to go into the motor.
PORTING THE CYLINDER ON ANY 2 STROKE, WHEN DONE PROPERLY, ENHANCES OVERALL POWER, BOTTOM TO TOP
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I already know our porting and exhaust power valve mods really help the 300 pull hard in the low to midrange RPM’s while adding extra punch on top, but that was just not going to be enough for this project. I wanted really big pull early in the RPM range. So the motor comes out of the frame and goes on the bench with a few ideas floating around in my head. After some careful measuring and calculator work, I decide the stroke can be increased 5mm with a few clearance modifications here and there. Increasing the stroke 5mm means moving the crank pin 2.5mm further to the outside of the crank flyweights. Remember, stroke is a reciprocating movement, so moving the crank pin 2.5 mm means 2.5mm extra going up, and 2.5mm extra going down, or 5mm total stroke increase.
STROKER ON LEFT, STOCK ON RIGHT. NOTICE THE CRANK PIN POSITION
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A 5mm increase does not sound like much, but the result will be more than just a displacement increase. Added stroke does more than just add displacement, it adds mechanical advantage to the push the piston has on the crankshaft. It also increases bottom end case pressure and push for the fuel mixture when the piston travels 2.5mm further into the case. The motor displacement will only increase from 293cc to 314cc, but the added stroke will make the low to mid RPM power a lot stronger than you might think.
SLIGHT SHAVING OF THE BOTTOM OF THE ROD GAVE JUST ENOUGH CLEARANCE
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Changing the stroke on the crankshaft will change the relative position of the piston to the crankshaft, so the whole assembly has to be re-balanced to avoid excessive engine vibration that would fatigue parts and vibrate bolts loose. There were a few other issues to overcome, like making a 2.5mm spacer to go between the cylinder and case, plus revising the porting to accommodate the 5mm additional stroke. The cylinder porting was done with an eye on working with the increasing stroke and adding even more to the low to midrange power. I also had to trim the piston skirt in two places to keep the piston from contacting the crankshaft at bottom dead center.
AFTER CLEARANCE MODS, THE PISTON SQUEEZES BY THE CRANK AT BDC. YOU CAN ALSO SEE SOME OF THE EPOXY WORK.
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While the cases were apart, I did some epoxy work (stuffing the cases) to increase bottom end compression, which will aid the punch this motor will have early in the rev range. When you decrease the volume of the engine crankcase area in a 2-stroke (stuffing with epoxy), more pressure is created when the piston comes down and this helps push the fuel/air mixture up the transfer ports into the cylinder above the piston. Stuffing the cases is basically filling void areas in the crankcase with epoxy, taking care to aid, not impede, the flow dynamics in the motor. And you can get some very odd looks from customers in the KTM World service dept when they see you putting epoxy inside your motor!
THE EARLY STAGES OF EPOXY WORK TO INCREASE BOTTOM CASE PRESSSURE, WHICH INCREASES POWER AND TORQUE
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With the porting and PV mods finished up, epoxy work done, crank stroked and balanced, everything is ready for final assembly. After careful clearance checking and assembly, the motor goes back in the frame and all the other parts are bolted back on the bike. By the time it was finished, that day was done, it was late and I needed some sleep. The next morning I did 3 heat cycles on the motor while doing my other chores around the store. The first thing you notice when you twist the throttle is the lack of vibration from the motor, far less than a stock motor, thanks to the crankshaft balancing. I would recommend this for anyone rebuilding or replacing a crankshaft in their bike. It is quite a difference that you have to feel to believe. The exhaust also had a distinct and different tone to it that the stock motor does not have, and everyone here noticed that right away. “Man that thing sounds strong” was a comment heard quite often.
BOTTOM END ASSEMBLED WITH STROKER CRANK
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RIDING THE 314 STROKER!
A little later, I am suited up for a first hand try of the big boy 314. Right away the extra power makes you smile big inside your helmet. This motor is awesome! Huge pull right off idle, and it never stops. The goal was strong bottom and midrange power, and we got that in spades, but a nice side effect was a big gain in the second half of the RPM range that was just ridiculously fun on faster and wider trails, or Jeep roads.
With the reworked suspension putting the power to the ground, the pull this bike has now is astonishing from idle to Warp 9. Riding 2 gears high and still coming off turns with authority, or rolling up rooty, rocky hill climbs at low RPM offers a lot more control and a lot less shifting. You find yourself in 4th and 5th gear almost all the time on moderately open trails. Come around a turn or come up on an unexpected hill at low RPM in a tall gear and you don’t have to downshift. Just a little stab at the clutch gets the motor pulling hard. It does not spin the wheel much at low RPM, it just applies the big torque, hooks up and goes, leaving you a more than a little astonished that you just pulled off that unexpected gnarly hill climb in 4th gear! Nice, long, controlled power wheelies are a breeze with this bike, and you find yourself making a little stab at the clutch lever coming onto a straight to easily loft the front a little bit and just avoid all the trail clutter with the front wheel. Very cool.
The combination of porting, pipe selection, compression, epoxy work, carb tuning, and the stroked crank, all make this one very sweet motor that pulls like a freight train. Save the expense for the stroked crank and you still have a very strong motor that will pull hard from idle RPM until “you-don’t-want-anymore” RPM. For the best bang for the buck, do the suspension first, then do the porting and the Hard Parts pipe/silencer combo along with the PowerNow carb insert.
Keeping a fast pace in the woods is easier and less tiring, thanks to the reworked suspension and a fantastic motor. The KTM 314 Project bike was even better than I expected and more fun to ride and race than any bike I have ridden in recent years. Definitely one of my all time favorite bikes!
KTM MAKES A GREAT MOTOR. KTM WORLD MAKES IT BETTER!
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