KTM To Build Moto3 Engine?

When the 125cc class is replaced by the 250cc Moto3 class in 2012, the last of the two strokes will disappear from the Grand Prix paddock. The demise of the 125cc two-strokes was largely down to lack of manufacturer interest: KTM had pulled out at the end of the 2009 season, Honda has not supported a factory effort for several years now, leaving only Aprilia on the grid, along with the Derbi-badged clones. In the hope of reducing costs and attracting more manufacturers to the class, the decision was made to switch to 250cc four-stroke singles, with a cap on the price the engines are to be sold for.

So far, the change has aroused the interest of the Japanese manufacturers, with Honda, Yamaha and Suzuki all rumored to be building a Moto3 engine, and now, Austrian manufacturer KTM could be interested in making a return to the smallest Grand Prix class, with Belgian MX magazine MotocrossMag reporting that KTM is looking at producing a specially tuned version of its SX-F 250 engine for use in Moto3. In its current form, as used for motocross racing, the engine produces in the region of 40hp, and with the addition of several specially lightened parts, the engine could be made to rev higher and produce more power, while still staying under the 10,000 euro maximum selling price.

In addition to the major manufacturers, several smaller engineering firms are also believed to be interested in producing engines for the class. Without the massive manufacturing base and standard MX engines to fall back on, producing a competitive Moto3 engine under the price limit is much more difficult, however, and it remains to be seen how many other manufacturers will enter. What is certain is that some of the chassis manufacturers already involved in Moto2 are also looking at producing frames for the new Moto3 class, with Moriwaki already touting their MD250H, and several other chassis builders currently working on Moto3 prototypes, their current stumbling block being which engine to use to design the frame with. Moriwaki's strong links with Honda are making it much easier for the Japanese manufacturer in this respect.

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So the SX-F 250 motor has a 76mm bore; I know there are a lot of variables but how competitive would the power output of such a motor be against a bespoke 250 motor that has an 81mm bore that can rev to the full extent that the shorter stroke will allow?

The 76mm engine would be about 6-7hp shy of an 81mm bike according to my rudimentary bhp calculations. Doesn't sound like much, but when you consider these bikes will make around 60-65hp (depending upon compression rules or the quality of the fuel), the KTM would have 10% less horsepower.

They will release a statement finalizing the rule structures, the minimum requirements for participation by a manufacturer and a commitment not to change the rules until after at least the 2nd year of racing. The initial Moto2 rules that were released by the FIM looked promising until Honda managed to take the class over with its spec engine. With no guarantee that this will not happen again in Moto3 companies will be rightfully wary of investing in the R&D of a new engine.


But if they were going to change to 4 strokes, I'm glad Honda managed to 'take it over'. Seeing a pack of over 10 riders half way into the race last week, with at least 7 different riders taking victories this season and 12 different bikes on the grid I'd say that from a competitive standpoint it's been a success.

With such a big 'experiment', keeping at least one part constant was good. This new class of racing just allows the constant to be controlled by a much more manageable amount of money. It's a good opportunity to, again, experiment with how to make racing sustainable. I could see moto2 going a similar route but the high cost of such a larger engine will be hard to swallow if a team makes the wrong bet. The low cost of the Moto3 option does leave open the result of it turning into a one-engine-make league based on product performance. Only time will tell, but one thing that is certain is that the deepest pockets are unlikely to be able to just buy the fastest bike.

I was working at PI on the weekend hosting a few rider events and noted a few things:
- Bradley Smith: "125s are at about 55rear wheel HP"
- Toni Elias: "The 250s were nicely matched horsepower to weight. Moto2 is not"
- I had no idea how much Moto2 was down on HP.

When I spoke to ex World Supersport rider Kevin Curtain this time last year he thought that the Moto2 bikes would have 180PS, but we didn't realise that aside from a pipe and airbox they would be basically stock. They sound great but really need more HP. I realise this is to keep costs down, but I also wonder whether that was to also ensure Moto2 remained slower than MotoGP. At the right track- or in the rain- that could be a reality.

I think if they severly restrict Moto3 and Moto2 in terms of HP or increased weight limits then they might be poor feeders for MotoGP. That may benefit WSS and WSBK riders when the 1000cc era comes about.

Why must they have more HP? I have seen this comment tossed around quite a bit and haven't heard any reasons. Anything you would like to share?

It's the whole racing thing. You may not understand it.

Tony Elias' take on moto2 (from mag.gpweek.com) is:

The other problem is the shortage of Hp punishes better riders and allows less experienced riders to join groups that take them over their heads. The engine is very slow, very very slow, much more than I thought. It means everybody can be fast. I think it is necessary for more power to see the difference between good riders, normal riders, bad riders. Now everybody is fast.

This from a guy with more experience than anyone else on the Moto2 grid.


We all get why faster is better, but not why faster is required. If you can shed light on that, please do.

I don't care that he's just won a top class Grand Prix and a Moto2 Championship, that sounds like a load of crap to me. One thing that riders cry for when they aren't a the top is 'equal equipment'. Everyone cries when they get passed by a bike with more power that they are the better rider but powerless to win. If winning by having a huge mechanical advantage is racing or the sign of talent then lets just pick our favorites at the beginning of the year and give them a double displacement advantage and everyone else has to use rain tires. I think Toni may have just been used to Spanish sponsors being able to buy him one of the better bikes back in his 250 years. He won this year because he was the best rider by far. If these slightly lower power machines highlight the CLOSENESS of the talent, I hardly thing that's a problem.

>>We all get why faster is better, but not why faster is required

I don't understand this comment. Do you not want things to get 'better'? If you agree 'faster is better' it is not a big leap to 'slower is worse'.

You asked for an example of why more power is needed. I give an example of an experienced rider, the guy who won the championship with races to spare. A guy who has no reason to bitch because he won! Yet you dismiss it as a load of crap. He was the best rider by far yet you disregard his opinion? His 250 days are a long time ago and he never did better than 3rd in the championship so I don't know about this Spanish sponsors getting him the best machinery idea.

How about Randy DP? At a later issue of mag.gpweek.com he says:

"The problem is ... the 250 was a very good bike to learn how to set. It was very difficult. It was a race bike. For me Moto2 is like a street bike. All the same engine, and if you don’t have the good frame you are on the back. It is a good solution because many rider is there, but to learn if you want to go to MotoGP I think it is not a good solution."

Another 125, 250, and premier class rider, but I'm sure he is full of it too.


DePuniet's argument is much more sensible. It's also completely different. Elias' doesn't add up. How can they argue for equal equipment when they are on the back foot and complain about equal motors to all when they aren't running away from the pack with some sort of advantage? Is he saying that anyone can ride fast on a 140 HP 4 stroke but only the best like him can ride fast on a 150 HP 2 stroke?

Yes, I would like more money. That would be better. More of good things is usually better. Would it be better for you if it came at the expense of you? Everything has a cost. I still don't know why the new class being faster than the last class is REQUIRED. By your logic, a race with 2 riders going 170 mph would be a better race than 25 riders going 150 mph. I think that could be arranged, but it would be a tough sell.

'Why must they have more HP? I have seen this comment tossed around quite a bit and haven't heard any reasons. Anything you would like to share?'

The thought of a purebred GP machine have less hp or power to weight than any street bike riding lardass is unacceptable. Also, the move away from the 500/250/125 recipe has again taken away the exotica and something not to far away than normal people can have access to. Therefore it still needs to seem better or something mortals could not easily control. Just my point of view.

I completely agree, a Moto2 bike just isn't exotic where the 250s were definitely an exotic bike.
While the grid is full, it seems that a lot of teams and riders have flocked to it because it is cheap and accessible now, not because they are looking to take the next step to MotoGP and have proven themselves worthy enough for the sponsorship.
So in that respect it seems to have lost some of it's Elite status.
Personally I think that ideally, they should be a full prototype series with engine and weight restrictions. Ha.

I hope that Moto3 doesn't go the same way, at least there should be a choice of motor. It would make chassis design more interesting.

MotoGP has shown that you can get as exotic as you like; except that nobody is buying.

More HP a good idea. But its works now doesnt it?
More RWHP means the set up has to be better.. teams with more money rise to the top!

But the best riders of HP the Australias would also come to the top!

Ain't NO WAY in the world a 250cc single 4 banger will see 60hp. The best 250F's now have about 36HP the same as a two stroke 125 mxer.
An Aprilia RSA125 is 54HP at the wheel.

In order to get anywhere near 50HP froma 250 your going to have to hack 1 cyl from an F1 engine and rev it to 18,000 rpm. F1 has max bore size of 96.4mm and max rod length of 111mm with a bore size of 81mm your going to limit valve size considerably.
However many smart cookies have tried this approach and failed miserably.That won't come in under 10,000 Euro's either.

If you'll double check your math, you'll see that a 250cc 4-stroke can make 60hp quite easily. The actual power rating will depend upon the FIM's compression regulations, but 60hp is not unreasonable at all. If a 250cc single achieves 1/4 of the 81mm 1000cc performance, it will actually produce 65bhp.

F1 runs 98mm bore at 300cc per cylinder and they original 2006 engines were operating around 20,000rpm. 81mm @ 250cc @ 16,000rpm is doable, imo.

It all depends on the rules.

Looking at the maths, a F1 cylinder at 20000rpm has about the same average piston speed as a moto3 cylinder at 16000rpm, about 26 m/s. Hardly a recipe for an inexpensive engine with long service intervals. I also don't recall anyone that has done it as saying making a competitive F1 engine is easy.

I'm curious as to your background. I've been racing a long time and think every engine builder I ever worked with or heard of would laugh at the statement 'a 250cc 4-stroke single can make 60hp quite easily.' Reading articles about engine performance and actually making an engine perform are two vastly different endeavors. While your numbers do 'add up' they are not representative of what is actually achievable.

Also, tacking a 'IMO' on the end of a tenuous statement does not validate it.


A GSX-R1000 in WSBK trim achieves over 25m/s. Suzuki has been running their 1000s above 25m/s for a half-decade now. Not only is it achievable, it's common. 60bhp for an 81mm 250cc engine is not a big ask from today's engine designers not even if they start with production engine.

The big hurdle to 60bhp ratings is that the manufacturers would likely not want to sell such technology (they don't sell WSBK tech) so it remains to be seen what they will do with compression rules or fuel rules.

The will to sell sensitive race technology, not the manufacturers engine building capabilities, will ultimately decide how much power the bikes produce.

Yes, gsxr1000. The same engine that blew up during the last WSB race. WSB engines last one race weekend at best and they don't make 240hp. The ones that last longer make even less. Now add 7mm to to the bore, which increases combustion time, yet spin it faster to decrease available combustion time. Eliminate the reduction of pumping losses between cylinders, exhaust pulse tuning benefits, and make the balance really bad unless you have a bunch of balance shafts which suck Hp. 50Hp if you're lucky. I've done a lot of work racing singles and saying 60hp from 250cc is not a big task just highlights your lack of experience.

The manufacturers don't sell WSBK technology? How does that happen when this year only two factories were directly involved and next year it will be one? All of these race teams are private organizations that build on production motorcycles that they purchased from said manufacturers.

The will to win, limited by the laws of physics and cashflow, will determine how much power they make, not the manufacturers' will to sell. Or more rules that have yet to be released.


Everything in WSBK is done under contractual lease. The teams do not own the bikes or the parts they race; especially not the electronics, and they are not permitted to sell any of their race bikes to other private teams who are not also under lease contracts with the manufacturer.

Furthermore, you and I are both acutely aware that the GSX-R didn't blow up b/c the piston velocity was too high. Suzuki were trying to avoid an Aprilia clinch so they ran stupid valve clearances in an attempt to massage the last 3-4hp out of the engine. It popped quite predictably. The bottom end is not the reliability concern on any of these engines. It's the top end that poses a problem.

In order to achieve 60bhp, the 250s will need MotoGP fuel and MotoGP compression technology. The manufacturers have never shown a willingness to sell their race compression technology. That is all. The laws of physics are meaningless if the manufacturers won't sell the technology. They can make 60bhp from 250cc, but they won't.

I wouldn't be surprised if they limit compression and revs in the rulebook or via homologation procedures.

The Moto3 class will almost certainly use a spec ECU, and they could also impose a rev limit as well. With those two factors in place, no need to impose a compression limit.

>>Furthermore, you and I are both acutely aware that the GSX-R didn't blow up b/c
>>the piston velocity was too high. Suzuki were trying to avoid an Aprilia clinch so
>>they ran stupid valve clearances in an attempt to massage the last 3-4hp out of
>>the engine.

I'm not aware of what the actual cause of their failure was. Are you? Mean piston speed is a rough number that tells us how fast all the various bits (including valves too) inside are moving. It seems like those bits were moving too fast to last that long. A Suzuki that makes about 214Hp (from the Alstare website) tries to make 218 and pops. That's under 55Hp per cylinder. So how is a 250 single (without inter-cylinder tuning aids) supposed to make more and last 3 race weekends?

>>In order to achieve 60bhp, the 250s will need MotoGP fuel and MotoGP
>>compression technology.


>>60bhp for an 81mm 250cc engine is not a big ask from today's engine
>>designers not even if they start with production engine.

Which one is it, 60 Hp is easy starting from a production engine or 60 Hp needs motogp fuel and compression (and motogp materials and motogp surface treatments, lifespan, etc) which makes it a motogp engine and not an 10k low cost engine. That's the whole point.

Most of the ECUs is use in WSB are Magneti Marelli (like suzuki's- from the alstare website) units that can be purchased and developed by anybody with the deep pockets. I've purchased ex-wsb parts so don't know why you seem to think they are all leased.

I'm not likely to continue responding on this thread as I don't see any benefit. When you can show an inexpensive long life 250 single making over 60hp I'll eat my words. Until then, it's all vaporware.


An Alstare Suzuki can make 55bhp from a single cylinder with just 74.5mm bore. Why are we still having this conversation?

The only thing you need to know is that the Japanese will not sell MotoGP or WSBK technology to the Chinese for 10,000 euros. Anecdotal science will not determine how much power these engines make. Company policy regarding sensitive race technology will determine how much power these engine produce.

Imo, they will be rev limited and compression limited to the neighborhood of 50bhp. However, according to the FIM's modus operandi, should they move to a homologation-based system for engine regulations, we will never know what the hell is going on in Moto3.

I'm skeptical of trusting a company like KTM to such a venture. Lest we remember what they did to Team Roberts and KTM's own 250 team just a few years ago. The fact that they abandoned both teams, mid-season, has forced me to never buy a KTM product.

Because the 125s make 50-ish hp and weight about 130-140 lbs. The 250 four strokes will be much closer to 200lbs and probably make less hp (especially if you consider the Moto2 power claims of 150hp and what was actually delivered). At some of the longer tracks watching these things go down the straights will be like watching paint dry!

When a bike blows by at 130 mph and another at 140 mph, do you think the 130 mph is slow? Is straight line speed what it's all about? Is this drag racing? What about if the two go by at 130 mph?

If HP is the end all, why not make them 450 singles? It's just as valid as the argument that says they have to be just as fast as the current class.

And I think it's a stretch to think that the difference in engine will result in a 60 to 70 lb weight difference.

Obviously there is more to it than power to weight and aerodynamics play a key role in top speed. But I think the reality is that in the GP classes, the bikes should be faster than similar bikes in national series. When you spend the weekend seeing the top bikes going over 200mph at the end of some straights then the bikes tat hit 120 will look very pedestrian by comparison.

As far as weight goes, the Moriwaki MD250 weighs 194 lbs dry and it is basically an rs125 with a 250 lump in it so the weight is in the engine. You can lighten it, but how much. I don't think you'd get 30 lbs off of it...

Comparing the KTM and Yamaha 2 stroke 125 (150 in the case of KTM) to 4 stroke 250 motocross bikes, they only weigh about 19 and 16 lbs different respectively.

The current 125s don't quite hit 140 at places like Catalunya. If they were slightly down on top speed but there were more than the usual suspects at the front I'd think I'd still be impressed with an even tighter than normal 125 race that only reached 130 mph. If the bikes are down on power the first few years and the CEV riders are out lapping them on a more powerful machine, it won't last for long and those riders should probably be in GPs. There aren't any other really equivalent national series.

I for one will really miss the 125 2 strokes. They were the perfect combination of power, weight, cost and simplicity for young riders to begin their carreer on. The lighter the machine the more safe it is (all else being equal) and safety is paramount when talking about any race competitor, but especially our children.

Besides, I grew up with the smell of 2 strokes and I will miss that as much as the amazing sound that only a 2 stroke can produce.

Agreed. It sounds like any rider who has raced both 125 2-strokes and 250 4-strokes has said how much better the 125s are as proper race bikes.

If the issue really is cost, then why didn't they stick with the 125s and 250s and impose the cost/engine distribution restrictions that they are now imposing on the 250 4-stroke manufacturers? If Aprilia hadn't jacked up the costs so much with the 125/250s then the other manufacturers would have stayed in, and there would be proper race bikes to feed into MotoGP.

As anyone who races MX knows, these 4-stroke bikes are incredibly maintenance intensive. Certainly much more so than the 2-strokes they are replacing.

Plus 2 strokes smell nicer!!!

These are the guys that pulled out of the US Red Bull Rookies Cup and broke the hearts of kid racers because they couldn't support their commitment.

Now they are to be trusted with GP3?

I don't know where people are getting the idea that KTM would be some sort of sole supplier to the league.