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Old 01-06-2010, 10:08 AM   #16
mutt2jeff
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Quote:
Originally Posted by jake28
Don't forget the marketing aspect of bike choice as well: Dakar, like any MotoGP, supercross event, or motorcycle tradeshow, is an opportunity for companies to show off the 'best and brightest' of their motorcycle stable.

If Honda, KTM, Yamaha,... want to sell four strokes, and there is no doubt that every company does, the racers will be atop four stroke race bikes.
KTM is very active in marketing its two strokes in enduro and off-road racing.
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Old 04-20-2010, 05:30 AM   #17
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Quote:
Originally Posted by neduro
I think a 2 stroke is not desirable for 3 reasons:

1) Half the Dakar is paved or at least untimed and open and boring, usually. That's a lot of km both for wear and tear and also for discomfort.

2) Power and power delivery: The big 4 strokes have an edge both on power and how it is delivered for carving up two track, which is the order of the day.

3) Fuel Economy: my 300, ridden at a fast pace and on the mainjet, burns substantially more fuel than my 530 ridden alongside it. Both are jetted to the best of my ability...

Don't get me wrong, I love the 2 strokes, but I'd hate to sit on one a few hundred klicks of pavement a day, between the good bits no less...
Hey Neduro,

When you refer to the 4 stroke having an edge are you refering in general to the larger bikes, 650cc plus or the 450's or 530's. Now that there is the 450 limit in place for pro's in 2011 and the rest of us 2012 onward can we disregard your point 2 or do you think there is still too much of a gap.

If a 300 KTM is close enough to the 450's in terms of torque etc we would just be left with comfort and fuel range.

When you say that the 300 is way more thirsty than the 530, what sort of riding did that involve. Was it a thrash or were you short shifting and riding the torque.

Neduro's comments or others very welcome.
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Old 04-20-2010, 10:48 PM   #18
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300cc 2 stroke in a rally...

It has been done (with varying degrees of success) and in light of the 450cc fourstroke restriction rule (2011/12 onwards in Dakar*) it would seem (as you point out) that it could be an alternative.

Here is a 1990 perimeter framed KX 250 (rally modifications and a KDX 250 motor) as ridden in the 1990 Australian Safari by Allan Cunnynghame to a 5th place (all XR600's in front of him).

(sorry about the faded old print)


The minimum fuel distance of that event was 300km (50 km's MORE than todays Dakar spec.) While it is true that did not include the same (fuel consuming) soft sand dune running that Dakar typically includes... but the bike still required a capacity of around 35 liters to go the distance.

The little KX/KDX was in it's element in the tighter or more technical sections (especially when the fuel load got lower into the stages), compared to the larger capacity fourstroke bikes of the day. Talking to Allan about it afterwards, he said that the hardest part of riding the thing in a rally (as Neduro alluded to earlier) was in fact; the long monotonous transports... the vibrations of the little 2 smoker were "mindnumbing" apparently.

This was 20 years ago... with some modern rally technology (lower COG tanks, cush rear hub etc.) maybe a 300cc two stroke is not such a silly alternative agains a 450cc fourstroke at Dakar*??

*The up to 700cc single fourstrokes are still (at the moment) allowed to compete in the other FIM rally events.


So barrier911, why not throw a larger tank, some navigation gear and a cush drive rear hub on an EXC 300 and head of to the next NRE with Hogwild and the boys to do some "real world" field research... ie. run it in rally conditions against other 450 and 690 cc rallye bikes?
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Old 04-21-2010, 05:12 AM   #19
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Quote:
Originally Posted by troy safari carpente

So barrier911, why not throw a larger tank, some navigation gear and a cush drive rear hub on an EXC 300 and head of to the next NRE with Hogwild and the boys to do some "real world" field research... ie. run it in rally conditions against other 450 and 690 cc rallye bikes?
Thanks! Troy, like I need any more encouragement to plan on entering the 'Big' one, Dakar, I mean. Now I've got you egging me on to rise to a challenge. I beat myself up every day deciding on what rally to enter next and which year to go for the Dak.

You may have seen a number of 4 stroke bikes I've built in to 'rallye bikes' on JMo's thread but I've never even ridden a two stroke.

The KTM 300 as a bike for Dakar interests me for a number of reasons....
  • It's different and would raise some interest. (hopefully not for all the wrong reasons) (Eg having to change a piston and rings at each mid stage re-fuel! )
  • Stories of the top end lasting upto 300hrs without work.
  • Runs cooler.
  • Weight.
  • Far simpler and quicker maintenance.
  • Ability to carry a top end overhaul kit, piston etc and repair on the fly. How many guys have gone out of the event with a holed piston or dropped valve.
I am guessing that the stroke and bore could be increased to add torque without even getting close to the 450 cc limit.
Higher torque should decrease revs, wear, vibration and fuel consumption. Or am I dreaming!!!!

As another first I believe it could also be 'Christinified!' That is AWD like my 08 530...
  • I know I could suffer the vibes for a Dakar finish and maybe more flywheel weight would help. Mr Renazco would be getting a call.
  • I know the Christini kit on my 530 dramatically reduces the requirement to rev in the soft sand, keeping the front wheel light and requiring a ton less fuel in those conditions.
  • I know Safari make a 9 litre rear tank or even the Meca twin tanks would help with some creative thinking to reach about 30 litres as a total.
Now I still need to decide which rallye to enter next, which year to enter Dakar and Now which bike to build next, thanks Troy!

barrier screwed with this post 04-21-2010 at 05:36 AM
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Old 04-21-2010, 06:00 AM   #20
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You might want to call Dave Fretigne over at Yamaha before you go too far down the two wheel drive route for a rallye bike...?

I know it's a different system to the Öhlins concept that Yamaha employed on the WR 450 F, but asisdes from the increased weight and some dubious reliability apects from having the front drive as well, there were some mixed reviews on the "high speed" handling traits in a rally application. No doubt though, it would give you better traction, climbing (and interesting to hear your increased fuel economy theory) in the soft sand dunes.

Yeah, I'd rather work on a 2 stroke, than a multi-valved, chain and cam driven, titanium wonder fourstroke motor out in a bivouac situation too...
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Old 04-21-2010, 07:39 AM   #21
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Humpf who keeps coming up with....

http://www.advrider.com/forums/showt...=473291&page=2

...these ideas for rally bikes....
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Old 04-21-2010, 08:10 AM   #22
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You don't want that Zabel/Maico/ATK motor in a rally bike. You'll be changing pistons 3 times a day!
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Old 04-21-2010, 08:15 AM   #23
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The intimidator...?

I'm not sure how you'll squeeze those 701cc's past the 450cc rule Pilbara...

But you're a resourceful bloke (the scrutineers failed to see that "extra" cylinder on your SE at the Safari a few years back )...


... so maybe some new 250cc "sideplate" decals at tech inspection and bombs away eh?!
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Old 04-21-2010, 08:30 AM   #24
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Quote:
Originally Posted by barrier911
If a 300 KTM is close enough to the 450's in terms of torque etc we would just be left with comfort and fuel range.
Having just come back from a few weeks of beating my 300 and 530 around the desert, I have an even fresher perspective on this than usual.

First, engine performance. On paper, the 300 and 530 aren't that far apart in terms of peak horsepower, especially when you consider the lower weight of the 300 as compensating for the few HP it gives up. Torque is not even that far off.

But, in the real world, they are miles apart. The 300 makes something approaching peak torque for just a couple thousand RPM, and is relatively weak elsewhere (this weakness is what people call "tractable" and makes it a real weapon in technical situations, because you can short shift it and it doesn't light up everywhere). The 530 makes great torque over a much wider range of RPM (aside: it is also great in the technical situations because it delivers that torque so subtly if you have good throttle control. The 300 really doesn't, it's a bit of a light switch, and you need good clutch control and to be in the right gear to get the best from it).

I haven't looked at a Dyno on my bikes, so take this with a big grain of salt... and jetting, exhaust port setup, and pipe choices can make worlds of difference, but if I had to guess, I'd say the 300 makes peak HP at something like 8K RPM, but doesn't really start pulling HARD until 5-6k, and runs out of steam shortly after it maxed out. It has useable torque below that, great torque for trail situations, but if faced with a big heavy rally bike trying to get max accel out of a turn, it would be underwhelming outside that band.

Furthermore, it comes on pretty hard and abruptly, relative to a 4 stroke. So it's not as easy to pitch and drift and slide on fire roads- it certainly can be done, but nowhere near as easily as the 530.

The 530, on the other hand, is incredibly smooth in how it delivers torque, making it easy to ride hard, and delivers useful torque from probably (again, a guess) 3000-9000 RPM. That's a band 3x as wide as the 2 stroke, even if the number isn't that much higher, it's a hell of a lot easier to keep the thing roosting forward.

Then there are the comfort elements of vibration and so on. My 300 is pretty smooth relative to the other open class 2 strokes I've ridden, but you start hating life not very far into a fire-road section, unless you are caning the bejeebus out of it. Then you're afraid enough not to notice the vibration. :-) That's not how you race a Rally, though.

Finally, with regard to maintenance, the 300 will go a bazillion hours without batting an eyelash in the hands of mortal riders, because they are generally in that underwhelming part of the torque band where trailriding actually happens. Start spinning it for hours on end at the torque and HP peak, and that story will change in a hurry.
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Old 04-21-2010, 08:41 PM   #25
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Quote:
Originally Posted by troy safari carpente

This may be his taken in Barcelona at the start of the '05 Dakar, KTM125

Dave and I saw this 125 in Barcelona. We passed him early on the very long road section through Spain on the 2nd day. Somehow, he managed to get ahead of us before the check at the finish. Lots of vans passed us on the 8-hour ride. Maybe he was relaxing in one and saving a piston. In any event, he was not at the finish in Dakar. For the longer stages, he had a big front tank like those on a KTM Adventure.

fun fun
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Old 04-21-2010, 10:29 PM   #26
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Dave and I saw this 125 in Barcelona. We passed him early on the very long road section through Spain on the 2nd day. Somehow, he managed to get ahead of us before the check at the finish. Lots of vans passed us on the 8-hour ride. Maybe he was relaxing in one and saving a piston. In any event, he was not at the finish in Dakar. For the longer stages, he had a big front tank like those on a KTM Adventure.

fun fun
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Once in Africa... he had to ride all the transports AND the selectives...

I recall it got to day three or four (where the first big soft dunes came into play) and then things got real tough. There were issues with not only the cylinder/piston (capicity/weight overtaxing the little motor), but even transmission issues. (There was a whole Dakarista movement following - and rooting - for Gerard to make it).

This raised conjecture as to the possibility of perhaps increasing transmission oil capacity (and a cooler maybe), cush drive rear hubs to ease the feedback impact from the rear wheel chatter on the gearbox and the possibilty to find a "sub 60 kg" rider to pilot the little 125cc two stroke (Gaston Rahiers dont grow on trees...).

It's all an interesting challenge to see if it "could" be done.
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Old 04-22-2010, 02:02 AM   #27
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Go with a 2 stroke YES, give it your best shot.

Absorb the wave of support from the thousands that would love to see you finish.

Add oil cooler, cush hub etc.....

But give yourself a chance and ride something bigger than a 125!!!!
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Old 04-22-2010, 11:08 AM   #28
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The first ATV to finish the Dakar was a Yamaha Blaster 2 stroke. I bought a Dirt Wheels magazine just because it had that article back in the pre-internet days where rally coverage came in such 1 page magazine blurbs 4 months after the fact. I believe the rider was a Frenchman. He had no support, but the Yamaha bike team took notice and lent him tools and such from time to time. The engine held for the whole race but the frame did require some welding along the way. He kept the oil injection intact and carried spare Yamalube.
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Old 04-23-2010, 12:54 PM   #29
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Plenty 2 strokes have finished over the years... including a 125! 40th overall went to Patrick Vallet on a Yamaha DT125 in 1984. A little street scrambler no less!!!
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Old 05-21-2011, 02:08 PM   #30
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Plenty 2 strokes have finished over the years... including a 125! 40th overall went to Patrick Vallet on a Yamaha DT125 in 1984. A little street scrambler no less!!!
BTW, the site www.dakardantan.com is very useful for any old Paris-Dakar info and pics
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