MXA’S TWO-STROKE MOTOCROSS SHOOTOUT! TM 250MX VERSUS TM 300MX – ITALIAN EXOTICA IN TWO DISTINCT FLAVORS

March 20, 2013
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Q: WHAT’S THE DIFFERENCE BETWEEN A 250MX AND A 300MX?

A: Since the TM 250MX and 300MX did not have any identifying marks telling which bike was which, it was impossible to tell them apart. Often we would send a test rider out to try a new fork settings on the 250MX only to watch they climb on the 300MX and take off.

The advantage of testing two bikes from the same manufacturer is that they share the same suspension, frame geometry, shock linkages, brakes, wheels, engine cases, carb and overall design. So, what is the difference between a 2013 TM 250MX and a 2013 TM 300MX?

    Displacement. The 300MX is a 294.6cc, while the 250MX is 249cc.
    Bore and stroke. The 300MX bore and stroke is 72mm by 72mm, while the 250MX is 66.4mm by 72mm.
    Summary. That’s it. The piston the TM 300MX is 5.6mm larger. It should be noted that almost every 300cc two-stroke made uses the tried-and-true 72mm by 72mm bore and stroke. Everything else on the to bikes is a spitting image.


The TM 300MX has a torquey, easy-to-ride spread of power.

Q: WHAT CHANGES DID TM MAKE TO THE 250MX AND 300MX FOR 2013?

A: Here is a quick look at the mods for the 2013 TM 250MX and 300MX.
    (1) Engine. There is a new clutch basket that has been treated with friction reducing. There are also new fiber clutch plates .
    (2) Mapping. As is common place in the electronic age, there is revised CDI mapping and updated carb settings.
    (3) Shifter. The shift mechanism has been friction coated for smoother operation.
    (4) Power valve. The power valve governor has had the bearings improved to reduced drag and improve throttle response.

Q: HOW DO THE AMERICAN TM 250MX AND 300MX DIFFERENT FROM THE EUROPEAN VERSIONS?
    
A: Previous TM’s have come with Marzocchi Shiver forks and Sachs shocks. Last year TM discovered that they could build their own shock absorber in the Pesaro factory that worked better than the Sachs and was cheaper. At a glance the TM shock looks very similar internally to a Showa shock. For most American TM riders the shock was considered an upgrade over the Sachs unit?largely because Sachs know-how was sorely lacking in the USA.

However, the Marzocchi forks were also a sticking point for U.S. buyers. It didn’t matter to them how well the forks worked or didn’t work?they wanted a brand name that they were familiar with. U.S. TM importer Pete Vetrano talked to the TM execs and told them that he wanted Kayaba forks on all American imported models. Surprise! His request was granted. Both the 250MX and 300MX have 48mm Kayaba Yamaha-style forks.


The TM 250MX hits harder and is more aggressive than it 300 brethren.
 
Q: WHAT DO THEY COST? WHICH ONE IS CHEAPER?

A: Hold on to your hat! A TM isn’t a mass produced machine built by an industrial giant. It is a hand-built bike that comes out of a family run concern. To their credit TM manufacturers as many parts on the TM as they can?including the aforementioned shock, but also the aluminum frame, billet hubs, CNC-machined components, billet triple clamps, hydraulic clutch slave unit and the complete engine. On their four-stroke models TM even makes its own throttle body. We state all of these exotic parts to soften the blow of the price tag. The Manufacturers Suggested Retail Price (MSRP) for a 2013 TM 250MX two-stroke is $8300. MSRP for the 2008 TM 300MX is $8450.


If you can tell the 300MX from the 250MX on sight, please tell us how to do it.
 
Q: WHAT DO THEY WEIGH? WHICH ONE IS LIGHTER?

A: The two bikes are virtual clones and they weigh the same. We expected the 300MX to be a little heavier because of the larger piston, but the weight gain was offset of the fact that the cylinder was bored out bigger. The TM 250MX and 300MX hit MXA’s scales at 219 pounds. You gotta give to get.


Hand-made in a small Italian factory, TM’s are quite rare in the USA.
 
Q: WHICH BIKE MAKES THE MOST HORSEPOWER?

A: No need to ask. The 300MX is bigger and thus the 300MX is more powerful. In or dyno runs the TM 300MX produced 46.00 horsepower, while the TM 250MX was down at 44.02.

Q: HOW DOES THAT COMPARE TO SIMILAR MODELS?

A: The dyno is not kind of either TM, but especially not the 250MX. The TM 300MX mimics a Yamaha YZ250 two-stroke powerband from 6500 rpm all the way to peak at 8200. After that the big piston of the 300 chugs down, while the YZ250 climbs another 500 rpm. If you throw the KTM 300EXC into the mix you get a blow out by KTM. The TM is always below the 300XC’s horsepower all along the power curve, but especially at peak where it gives up over three horses. Since the 250MX is the weak sister of the two?it loses to the KTM and the YZ250 by even bigger margins.

Q: HOW ALIKE ARE THE TWO ENGINES?

A: They are completely different. Diametrically opposed to each other. Night and day. Abbott and Costello. Dr. Jekyll and Mr. Hyde. We expected as much when we saw the spec sheet?you can’t increase the bore by over 5mm and not drastically change the engine’s torque curve, powerband and rev range.


TM claim to two-stroke fame came from their World Karting Championships.
    
Q: WHAT IS THE 250MX POWERBAND LIKE ON THE RACE TRACK?

A: When the 2013 TM 250MX comes on the pipe it hits hard and revs far. It has the kind of jolt that you expect out of a high-tech, high-power, 250cc two-stroke. It is very fast and, if you play gun-and-run with it, it is a effective weapon. It does require that the rider be either very skilled or an old-hand at two-strokes. A transplant from a four-stroke, will corkscrew himself into the ground very quickly. This is not an easy bike to ride. It demands constant attention from your left foot, throttle hand and clutch hand. Going fast on the TM 250MX is a ballet of lightning quick movements?shift, clutch, rev and repeat.

Making matters more difficult, and by that we mean worse, is the lack of an effective low-to-mid transition. You can never roll the throttle on and glide through a corner at half-throttle on a TM 250MX. Instead you have to hammer the throttle and jump up on the pipe. The transition from low-to-mid is quicker than the light in a home-schooled racer’s eyes going out at a spelling bee. It goes from no power to max power in the blink of an eye.

A word of warning. If your clutch hand doesn’t have a fast twitch muscles, don’t even borrow a quick spin on a TM 250MX in the pits. It will only embarrass you.

Q: WHAT IS THE 300MX POWERBAND LIKE ON THE RACE TRACK?

A: Incredibly pleasant. The MXA wrecking crew knew going in that there was no way that the TM engine could push the amount of air that the 72mm piston moves with an alacrity. The 300MX revs much slower than the 250MX, is blessed with abundant low-end and has zip, squat, zero top-end. It starts dropping off at 8200 rpm and is a done deal by 9500 rpm (the 250MX will rev to 10,500).

In comparison, the TM 250MX works in the upper ranges of the power curve and the TM 300MX works at the lower edges. There is the illusion that the TM 250MX is faster than the 300MX. This false sense of power is caused by how hard the TM 250MX hits. The explosive power delivery makes the 250MX feel a lot faster than the mellower power delivery of the 300MX. But the 300 makes more horsepower, has a broader powerband and is easier to ride. When you start throwing turns, off cambers and ruts into the equation the TM 300MX shines even more. It never falls off the pipe. It is torquey, smooth and wide. It doesn’t rev, but guess what? It doesn’t need to rev. It does things that the 250MX can’t do?like go around a slippery corner at quarter-throttle. It doesn’t need any help from the clutch.

Every MXA test rider preferred the 300MX’s broadside of low-end power, its metered output and stronger pull into the midrange than the gun-and-run 250MX’s burst of power. Oh, test riders could go fast on the TM 250MX, but at what price glory? They say that there is no rest for the wicked and the same can be said about the wicked midrange bark of the TM 250MX. It was taxing, mentally and physically, to ride. On the other hand, riding the 300MX was a no-brainer. It didn’t ask for your soul before rewarding you?it went fast without divine intervention.

Q: WHAT MODS SHOULD EVERY RIDER MAKE?

A: We know this will sound strange, but both bikes need to be geared down. Paradoxically, both the high-rpm 250MX and the low-rpm 300MX benefit from one more tooth on the rear sprocket (from a 49 to a 50).

How can that be? It’s simple. The weak low-end of the 250MX is just too mellow to work with. It is true that gearing the bike down will shorten the overall powerband, which is already short, but at the same time it also shortens the part of the powerband that doesn’t work more than the part that does. Lower gearing makes it much easier to go from gear to gear without bogging between shifts. It didn’t eliminate the need to use the clutch, but it lessened it.

As for the 300MX, it’s torquey low-end style of power often felt like it was taking too long to get to third gear. Adding a tooth to the rear sprocket made the power more focused and even though some test riders felt that it made them run out of power sooner, this was not the case because the tighter gears allowed every test rider to shift to third gear sooner to take advantage of the torque.

Q: WHAT WERE OUR BEST TM 250MX/300MX JETTING SPECS?

A: Here’s what we ran in the 38mm Keihin PWK carb (the stock settings in parenthesis)
    Mainjet: 185 (182)
    Pilot: 50
    Needle: NOZG
    Clip: Third clip from top.
    Air screw: 1-1/2 turns out.
    Notes: Depending on your local climate you might want to drop one size on the pilot jet, but for our SoCal race tracks we used the air screw to iron out any blubber off the bottom.

Q: WHAT ARE MXA’S RECOMMENDED 250MX/300MX FORK SETTINGS?

A: The TM 300MX and 250MX share the exact same suspension components and setup. And, we didn’t like them. The forks were incredibly harsh. This seems to be de rigeur when European companies adopt Yamaha’s Kayaba forks. Husky has the same harsh forks on their TC250. We know that the forks are capable of turning in good performances, but the Italian settings are way off. Here’s what we ran in our 250MX and 300MX (the stock settings are in parentheses):
    Spring rate: 0.43 kg/mm
    Compression: 19 clicks out (14 clicks out)
    Rebound: 12 clicks out
    Oil Height: 340cc (350cc stock)
    Fork leg height: 6mm up
    Notes: According to TM, the suspension settings come directly from the numbers used by their factory riders. That would be like Suzuki putting James Stewart’s settings in every production RM-Z450. As they are setup, TM’s Kayaba forks are too stiff, too harsh and ride way too high in their stroke. We lowered the oil height by 10cc to get them closer to the Yamaha specs. Plus, we ran the clickers as far out as possible.


TM builds their own shock absorbers.

Q: WHAT ARE MXA’S RECOMMENDED 250MX/300MX SHOCK SETTINGS?

A: From the first test rider to the very last, every one of them tried to turn the high-speed and low-speed compression clickers farther out…but they wouldn’t go any further. That didn’t stop them from trying. This is a dead shock that even when it is moving, doesn’t feel like it is. The best solution is to turn not only the high-speed and low-speed compression clickers out, but be daring with your rebound settings as well. Stock is 14 clicks out?we went to 24. The lighter rebound will soften the compression stroke?because there is crossover in the valving stacks. Here is what we ran for our test riders (stock settings are in parentheses):
    Spring Rate: 4.8 kg/mm (5.0 kg/mm)
    Hi-compression: 24 clicks out (14 click out)
    Lo-compression: 21 clicks out (14 out)
    Rebound: 24 clicks out (14 out)
    Race sag: 105mm
    Notes: First and foremost you need to get a shock spring that is perfect for your body weight. The stock spring works for riders form 175 to 200 pounds. After setting the sag at 105mm, check the free sag. If it is less than 30mm got to a stiffer spring and if it is more than 40mm got to a softer spring. Once you have the best possible spring, turn the clicker all the way out and then start talking to you local suspension guru about revalving the TM shock.
 
Q: WHICH BIKE HAS THE BEST HANDLING?

A: You might think that they would both handle the same, but they don’t. Every MXA test rider insisted that the 250MX handle better than the 300MX. We attribute that to the decreased torque and the lighter rev of the 250MX when coasting into corners. The lack of vibes and minimal loading in off-throttle situations made the 250MX feel lighter, quicker and more agile.

Although both bikes handle very well, they were hampered by the front forks. Until we began removing oil from the forks, the front end wouldn’t settle. And without any appreciable dive on the entrance to turns the TM’s were ungainly at turn-in. However, even with that limitation they were still raceable. Just not as impressive as they could be.


 
Q: WHAT DID WE HATE?

A: The hate list:
    (1) Preload ring. TM uses the KTM clamp system, but with an aluminum preload ring instead of nylon. The preload ring is very hard to get to and it never truly locked the shock down. We would set the preload ring, lock the Allen bolt down and then after the moto the Allen bolt would have spun to the other side of the shock (where we couldn’t get to it). No problem, we just grabbed the spring and spun the Allen bolt back to where we could reach it?all without loosening the Allen        (2) Sprocket bolts. There are nine bolts holding the sprocket on. Nine!
    (3) Gearing. Both bikes work a lot better when the ratios are tightened up.
    (4) Radiator cap. The radiator cap sticks up above the radiator shroud. Last year we lost two radiators caps. This year we drilled a hole in the flange and safety-wired the cap on.

Q: WHAT DID WE LIKE?

A: The like list:
    (1) Exotica. This bike is a thing of beauty. No, not the graphics or plastic…the workmanship.
    (2) Front brake. The front brake uses a Nissin master cylinder with Brembo caliper and a 270mm rotor. That is 10mm bigger than a KTM brake.
    (3) Map switches. There two maps in the ECU. We ran both bikes on map 2.
    (4) Gas tank. We loved the translucent gas tank. We never had to wonder if we had enough gas. We could see it. Plus, the whitish translucent tank looked good with the white and blue TM plastic.
    (5) Hydraulic clutch: Very sweet and we used the heck out of it.


 
Q: WHICH ONE WOULD WE BUY?

A: As shootouts go, this one is very simple. We aren’t worried about which one has the best suspension, best brakes, best ergos, best clutch or lowest weight. In every significant category, save one, these two bikes are tied on points. It all comes down to the tie-breaker…and that is the powerband. There is no riddle here?every MXA test rider preferred to race the TM 300MX.

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