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Discussion in 'Racing' started by MitchMan, Jan 4, 2010.
...these ideas for rally bikes....
You don't want that Zabel/Maico/ATK motor in a rally bike. You'll be changing pistons 3 times a day!
I'm not sure how you'll squeeze those 701cc's past the 450cc rule Pilbara... :huh
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?!
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.
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.
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.
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!!!!
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.
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
Just to resurrect this thread I started a couple of years ago, are there any 2 Strokes in the 2013 Dakar?
The Bultaco is back.
LUIS... number 150 riding a ktm/jvo 150
The Bulty is Back?
Cool. I read an article onthe bloke / the bike, I think in Enduro Extreme, and got the impression he wasn't coming back for a few years.
2ts, would have no more problems than a 4t, in finishing. Especially when modern ones come out. Such as a 400 /450cc - LCed, PV'd of course - either Carbed or EFI / DFI/ Whatever new tech bikes came out. Auto lube, would be a boon - an ECU controlled Auto lube, could deliver oil in the appropriate ratios, for the loads / revs being used. Not hard to carry oil enough for a day, or for quite a few days.
Another thing a modern 2t could / probably will have, is a counter balancer. Set up using an existing spinning shaft, like what is used on the latest KTM, and you have very little extra complication / weight.
Two Strokes are not more prone to vibration than a 4t. Try riding a 4t that hasn't got a counter balancer some time, boys, and you'll get an idea of the vibration that a 4t can bring you........
Like ES, Auto Lube, and Counter Balancers will be a part of many modern 2 strokes. Along with DFI / Smart Carbs (for more traditional simplicity of the 2t) or "Whatever Technology" is used to make them clean enough to pass legislation.
The EXP, was an AR equipped bike. Honda's take on cleaner emissions, and smooth running of a 2 stroke. It used trapping valve technology, to enable it to 'diesel', thus not running the spark plug all the time. The Trapping valve, prevented re emergence of spent exhaust gasses into the combustion chamber, which contaminated the 'fresh charge', and causes misfiring - the uneven running that you have under constant throttle, under light loads. So - that, and a counterbalancer, can make a 2t as smooth as Emma Stones bottom.
The Trapping valve, also retains fuel charge, so it's not going straight out of the exhaust port, raises the compression for the 'dieseling' feature, and also ensures very good combustion / full burn of the mixture. Hence, seriously better fuel consumption.
I worked at Off Road Imports, for some 5 (6?) years, on and off, so I got to be involved in a bit of the OZ Safari. I still tend to call it the Wynnes........ One year whilst I was there, Olle Olson left his girl friend (now wife?) at Roscoes house for the duration.
Whilst I was there, Herbert Scheck (sp? - I should know, as I've been aware of him since the sixties) did the Dakar with his Daughter - to Water Boy for her. On a 500 Maico . Not sure if his Daughter was on a 500, or 440 / 400 / 380?. I think she broke her arm, and both retired after that. Speaking to him after, he said a big thing he learned, was that they could have had Much smaller tank capacities. The fact that the bikes were Much lighter than the Multi Cylinder , And the Single Cylinder 4ts, and had equal / more power, and more torque, meant they weren't being screamed, like the 4ts. They were "tractors", if I remember his words correctly.
The EXP 400s - 400cc 2 Strokes - with the AR Technology. I read of them as having used Carbs, EFI, and DFI. I believe they ran Carbs. For the same sort of reason as, up till recently, many Dakar bikes used carbs - simplicity..
They had the same Torque level as the 780cc Work Honda Twins, less HP, but had a better power to weight ratio. 100 / 150+lbs lighter, depending on who wrote the article. Plus, less fuel needed to be carried.
I think, that it won the smaller capacity class, and got 5th outright. I thought it was Richard Sainct that did that, but I've had difficulty in finding confirmation of my diminishing thought processes.I'm getting old....... Nope, it was Jean Brucy - winning the Experimental Class (according to the current HRC Dakar Team Manager).
The AR Tech was used on the later models of the CRM250 - the CRM250ARs. So, Honda did make use of the Tech.
Then, they finally became, as Soichiro Honda always wanted them to be, "All Four Stroke, All The Time". And other manufacturers followed suit.
Troy might know who it was - I seem to think it might have been Alfie Cox - well, a South African - but, one year of the Wynne's, there was a KX500, complete with a Down Pipe, entered. I don't think it finished. When I watched it doing the Prologue at Amaroo Park, I thought to myself, "I hope they've got a LOT of spare pipes with them".
I think a 300 could finish, with the right rider. But, things like fuel, make it difficult, I'd assume (though, what did the Bulty Bloke and The KTM200 bloke do?). I don't think there's a limit to top ends - but I'd only think it would be down to dusting the induction system, Jetting (Smart Carb?/ Lectron Powerjet? ) / Heat issues. Bigger rads / fans, like the 4ts use, can easily be fitted. Leaving the vibration that is just part of it being non counter balanced. A good program of balance factor research could help with that . Perhaps a counter weight type flywheel, for different flywheel / balance effects at different revs could be tried?
But, it's something too different, for most blokes to consider, let alone risk. It would still be a 300 - so, caned on transports. A 300cc 4t would be similarly - well more - prone to getting a hiding. Fair Enough, not wanting to take the risk - it's a hellishly expensive endeavour, the Dakar, without adding a big unknown to the equation.
Now, that Honda EXP engine, slightly updated, in a modern chassis, with an "Alien" or two on them - and you could kiss the 450 4ts arses goodbye, barring crashes / injury.
The Sth African you are thinking of was a guy from France named - Luc Grajwoda - he made a habit out of riding a monocoque framed KX 500 creation in the Dakar and various other rallies in the early to mid nineties...
The 1992 Australian safari was one of them
And above is a photo (taken by moi) from the very prologue at Amaroo park that you remembered...
The thing used to vibrate that much that it often split/fractured the welds on the chassis and aluminium fuel tanks/subframe construction... and as i recall his eyeballs were still going up and down a half hour after he climbed off the thing at the bivouac of a night...
There are quite a number of them. But then, I have a feeling that they should be place in their own category as well as other bike types with identical features. This will make the races more exciting and with more reasons to associate them. Managing the races will also be enhanced in that their will be ease in handling different biker in different categories..
Yes, and he finally managed to finish on a 150cc KTM 2-stroke... amazing.
In Dakar conditions which would use more fuel....Luis's 150 or a 300 two stroke?
Anyone know the size of his JVO rear tank and what tanks he used up front either side of the relocated air filter. IIRC he has some alloy tanks made for the front.
Anyone guess at a total fuel capacity and if he regularly ran out of fuel before the end of the longer stages?