Curt Winter sent over a few photos of his latest project. This one uses Harley Davidson Twin Cam power, Ohlins suspension, Brembo brakes and BST carbon fiber wheels. I think he’s come along design wise from his previous Warhorse. The undertail exhaust looks better, the rear section, it’s all developing nicely. It’s still in the very early stages but you can get a pretty good idea of where it’s going.
If you think big twin American power in a sport bike is a good idea, check out his website.
More photos and link below:
Link: Big Twin Racers
todd says
It’s been said before, there are more powerful / lighter engine choices for a sport bike – but it’s nice to have something new and different and maybe H-D or Victory will start to take notice. The bike looks nice and the craftsmanship looks right up there with the best of them. All the best to Curt Winter.
-todd
Sid says
Thanks Paul for introducing Curt to your readers more than 2 years ago (?) and keeping us up-to-date on the last 3 bikes. I look forward to seeing more….Victory 100″ or 106″
I think big twin torque is a great idea for a sport-streetbike.
Scott says
Could someone explain to me why a V-Rod Motor would not be a good choice for this kind of bike?
hoyt says
I don’t think anyone said a Revolution engine isn’t a good choice; but an air-cooled, stroker motor is still a good choice.
I’d order a BTR with a Victory engine or an HD 103″. I’d probably go with a Victory engine for its more compact drivetrain, unit-construction, stellar EFI, etc.
todd says
I didn’t say it wasn’t a good choice, I just said there were more powerful (greater torque) motors to choose from if you weren’t stuck using the V-twin design. Not to get into another torque debate… like I’ve said, it’s all been said before (reference the Wakan posts).
-todd
hoyt says
What engine attribute plays into the roll-on power?
In top gear from 40-60 or 60-80 mph, what factors in more – hp? or torque?
Curt Winter says
Usually anything above 60 mph is all about horsepower.
RY says
I like the Idea of this , Why has Harley not done this. as for horse power and tech for this engine , have you opened a American parts catalog latley? With the proper gearing and a six speed trans you can turn that big twin torque into raw speed. I want one of these, or maybe two!
todd says
I don’t understand where the misconception of V-twin torque comes from. Maybe Harley Marketing is really doing its job well.
Look up the numbers, ride a comparitive test. A four cylinder engine is capable of providing more torque than a twin at all RPMs. The fact that the OHC four is usually capable of twice the RPM allows even a wider power band than a push-rod twin.
There is no magic involved with a V-twin In fact, everything in its design (especially the typical Harley design) limits its ability to produce as much torque as a comparable four cylinder engine.
1. It only has one (1) intake valve per cylinder.
2. that intake valve has a very large diameter, limiting intake velocity and fuel suspension, especially at low RPMs.
3. It only has one large throttle venturi, a problem for the same reasons above.
4. the intake tract splits into a “Y” with a hard 90 degree turn, again, creating a loss of intake velocity and a decrease in fuel suspension.
5. the intake of the carb is sticking out the side of the bike limiting velocity stack length and air box size.
6. It has very large diameter pistons which limits compression ratio and encourages pinking and improper flame propagation and incomplete cumbustion. Larger pistons also create higher piston crown temperatures, greater ring growth, and blow-by.
7. It only has one (1) exhaust valve creating similar torque reducing problems as the single large intake explained in item 1.
8. Having only two valves makes it necessary to offset the spark plug to one side creating even more combustion inefficiencies (unless twin plugs are utilized).
9. They typically have very large diameter and short length exhaust pipes for that “booming” sound and “fat” look that is so popular. This reduces exhaust speed and scavenging often resulting in higher head temperatures.
10. A twin has fewer power pulses per revolution and heavier pistons/rods losing torque to the requirements of accelerating greater masses and heavier flywheels.
11. etc…
Like I said, there are better engine choices with even more torque than a V-twin.
-todd
p.s. I don’t like inline multis but I can appreciate the amazing horsepower AND torque they provide.
todd says
Top gear roll-on tests? Come on. Top gear on a V-twin is designed for only breaking 100mph. Top gear on an inline multi is designed for reaching 186mph. Even then, at 60mph a Hyabusa top gear roll on is still quicker than a Road King.
Tell me, which bike has greater torque, more accelleration, and a wider power band: Bike A that can do 0-60 in 8 seconds (using all 6! gears) or bike B that can do the 1/4 mile in 8 seconds in second gear?
-todd
Sean says
My father’s Moto Guzzi Le Mans would toast his mate ZZR round the corners, simply because he had torque down low. The ZZR would blow past him when he got into the straights, and he could hit that 7000RPM magic-line, but come the next set of twisties and the Guzzi had him. You can quote the Hayabusa’s power all you like, and you can say that an inline 4 has a wider range of power than a V-twin, but it’s a common occurrence when riding a 4 to drop down a cog or two to overtake, whereas with a V-twin you just pull the throttle open.
To quote a Harley vs a Hayabusa is inherently unfair. You have one of the most powerful bikes in existence, bred for speed and built for power, against something that is obviously, and at times openly, made for looking good, sounding good but only really for riding down to the pub. A Harley is a comfortable, long distance tourer, and a Hayabusa is an uncomfortable speed demon.
Oh, one last shot. My old man’s Guzzi topped out at 230kph. Most certainly not designed solely for breaking the ton. Hell, my 250 single does that.
Curt Winter says
Wow Todd, I think someone lied to you. What you are explaining is the difference between a high rpm engine and a low rpm engine, both efficiant by design. Think about this. A Harley V-Twin will make 100 lbs ft of torque, it starts making its usable torque at lets say 1000 rpm and reaches it’s peak at 5000 rpm. Thats a usable spread of 4000 rpm. A high strung inline four will rev to 11000 rpm, it starts making usable torque at maybe 9500 rpm. Thats a torque range of only 1500 rpm, and it may only make a total of 50 to 60 lbs ft. of trque at it’s best. Thats half what the V Twin makes and it has to be spin at over double the rpm. Now you tell me which engine is more efficiant.
todd says
are you comparing a 850 lemans with a 600cc kawasaki? That’s what I call unfair. Still though, look at the facts:
ZZR= 32 lb-ft @ 3500, 46 @ 11k, 36 @ 14.5k (or wherever the rev limiter hits)
850= 25 lb-ft @3500, 49 @ 6800 peak torque
So the Moto Guzzi with a 42% capacity advantage only has a 7% torque advantage, never mind that it has a 12% defecit around 3500RPM or a much narrower power band. I’d still take a Guzzi over a Kawasaki any day.
Yes a Hyabusa motor compared to a Harley motor is an unfair competition. But isn’t that what everyone is doing? Didn’t Curt Winter just put a Harley motor into a sport bike chassis? Why then shouldn’t we expect to use a sport bike engine? It’s different. It looks lean and cool. It sounds neat (at least when you look at what it is, otherwise it probably sounds just like every other harley). It’s something you just can’t go down to the store and buy.
People say they like the torque of a V-twin. But that preference is hard to justify when there is even more torque available in an inline four, sometimes much more. But with the four there’s an additional benefit in the likes of two or three times the horse power and twice the RPM range. They usually handle better and are more comfortable to boot.
Yes, I like Curt’s bike. I’d probably build one too if I had the time and money. But I wouldn’t have any grand dillusions that it had more torque or even handled better than a comparable sport bike. I would build it to be different, to have something that not everybody else can buy, to show myself that I can… and to be featured on the pages of The Kneeslider.
-todd
Curt Winter says
Todd, just get on a big V-twin and twist the throttle man. That low revving grunt that rips your arms out of thier sockets as the bikes rear end is stepping out is whats called torque. Meanwhile on an inline four when exiting the same turn waiting for the powerband to kick in carefully watching the tac and thinking to yourself, c’mon, when the tac gets to 8 grand this thing will really start to take off, just a few more seconds, then as soon as the motor begins to rip, it’s time to shift and you repeat this pattern untill your either out of room or gear. All the while the big V-twin is just now grabbing second. It’s no illusion that these motors make more torque than an inline four, they just do, it’s as simple as that.
todd says
Crt, where do you get your info from?
A 1450cc HD twin cam motor peaks @ 66.9 lb-ft at 3,800 rpm (72 for EFI). Look it up.
A 1352cc Kawi ZX-14 peaks @ 106 lb-ft at 7,500 rpm (113.5 was the highest chart I’ve seen for a stock ZX). sure that’s high but at 3,800 rpm the smaller ZX motor is cranking out approximately 70 lb-ft of torque. If it puts out as much torque at the bottom of its range as the Harley puts out at its top why would you need to wait until 9500 rpm for “usable torque”? If anyone ever lied to me about this I think Curt just did.
I can’t answer to the “1000” rpm claim. I’ve never seen a dyno chart read below about 2,200 rpm. I chose a ZX-14 because it was the closest in capacity to the HD. I did not choose to site twin cam 95 or 96 engines because that is an even greater capacity disparity.
-todd
todd says
BTW Curt, I live a couple miles away from your shop in Hayward and I think I’ve met you a while back at one of those “American Sport Bike Night” in San Leandro. Do you remember a Trail 90 with a side car? Take care.
-todd
Curt Winter says
No, I think the last time I made it out to a bike night was when they had it at a bar in Dublin. Man that’s been a few years ago, I think it was back in 98 or 99. I didn’t bring one of my bikes but I brought a bike that I built for my cousin. It was an early iron head sporster that I made a frame for and we used cbr 600 suspension on it. The bike was red and the wheels were black. It was a cool looking bike, slower than you know what but it handled awesome. I would really like to make it to one of those again, are they still at the Straw Hat Pizza off Washington. When do they start or are they already going on?
Sean says
I think the 250cc difference is a world away from HD vs ‘Busa. Let’s face it, we can argue statistics and numbers til we’re blue in the face. The only real way to tell is to get on the damn thing and ride til we’re blue in the face from windchill. I sure as hell know what I’d prefer to do.
Keith says
Put a 155″ 190hp vtwin in that thing from rrcycle.biz and that thing will fly.Forget the Harley 88,95 ” twin cam , but wait , does’nt Ducati have allready mastered the vtwin ?
todd says
American Sport Bike Night is held the first monday of every month at Straw Hat @ 6pm. Last month I missed an update on Buells dirt bike plans. This next one in a couple days will be vintage bike night so I’ll bring my R75/5 if I make it. Next month is British bike night but I don’t think I’ll have my BSA cafe bike ready by then.
http://pirateradiostation.weblogger.com/stories/storyReader$669
-todd
Curt Winter says
Todd, I’m going to try and make it out to the bike night on Monday, I’ll bring the Evo powered bike. Hope to see you there.
hoyt says
Todd says, “Top gear roll-on tests? Come on. Top gear on a V-twin is designed for only breaking 100mph.”
Exactly my point. We’re talking about a streetbike. A bike specifically built to ride the hill/mountain areas rolling through one corner into the next. The stats & high revs is not what this bike is about. It is about 20 – 30 mph suggested curves, one after another and the engine running at a low rpm, but delivering good usable power – Something the Kneeslider rightfully termed “Accessible Power”. What good is the power if you have to operate in a smaller margin of error?
Todd says, “Top gear on an inline multi is designed for reaching 186mph. Even then, at 60mph a Hyabusa top gear roll on is still quicker than a Road King.”
Ok. We are not talking about a Road King or a Hayabusa.
Todd says, “People say they like the torque of a V-twin. But that preference is hard to justify when there is even more torque available in an inline four, sometimes much more.”
I don’t have a problem justifying the Guzzi torque at all. It speaks volumes for itself on the street. Although my friend’s R1 is fun to experience sheer acceleration on a straight stretch every once in awhile, i need assurance that there will be no police to cost me more money in insurance. Having the amount of torque delivered only the way a twin can deliver it through the curves is the preferred tradeoff.
Everytime this subject comes up, you raise the in-line 4’s attributes as though Curt or Wakan’s purpose is to out perform an in-line four in all areas.
That is not the intent.
Power delivery, packaging (narrow, no plumbing), sound, etc. combine into making a unique, performance bike for the street. In this case, you could also add serviceability and a strong market for v-twin bikes. Considering the custom v-twin market, Curt’s concept is in a prime position.
What are the torque numbers of an air/oil cooled in-line 4?
Sean says
I agree entirely with hoyt. I think this is a corner carver, a kneeslider if you will. Also, the curve of power on a 4 is slightly less accessible than in a V-twin. With a twin, you always know that there’s a solid, dependable line of torque. It’s not going to all of a sudden go crazy at the back wheel, it just keeps going, nice and smooth all the way round. The reason why most racebikes are 4s? Because those racers have learnt to ride that crazy period. Forgive me for digressing, but the reason why a lot of learners crash? Because they’re on those homologated racebikes, and they haven’t learnt to ride the smaller powerband. Give me a 250 V-twin that can burn round the corners. At least it’d help replace the sluggish singles or the insane fours that seem to be the norm in my capacity range.
todd says
Thanks for clearing it up Hoyt. I thought everyone was saying the V-twin was a great choice because of its power. I merely intended to demonstrate that the V-twin does not corner the market on power nor torque.
I also read that the torque of an inline four is “inaccessible” or “sudden”. I’ve ridden many inline fours and the characteristics being described sound much more like a late-seventies / early eighties 250 motocross bike. I’ve only experienced strong, linear power from a four.
Torque is a factor mainly derived from capacity and efficiency. A 600 single will have pretty much the same torque as a 600 twin, triple, four, six, etc. at the same RPM. Generally as the number of cylinders increase, the size of the inlet tracts decreases providing more torque. Harley definitely designs their motors for the greatest amount of power for their design. Why else do you think they no longer offer 750’s?
I already said that I like Curt’s bike. I like it a lot and I would probably want to buy one over a Hyabusa or a ZX-14 if I had the cash. Actually I’d like to build one myself but with a KTM 690 single…
-todd
hoyt says
“I thought everyone was saying the V-twin was a great choice because of its power.”
Most people agree a v-twin is a great choice because of its power when the discussion is about riding the bike through corner after corner. (note: this doesn’t mean it is the only choice. There are other factors involved that make this a preferred choice).
Most of these people “get” this and don’t care about the straight-line acceleration.
“I’ve ridden many inline fours …” —
Have you ridden a new big twin from Victory, HD or Guzzi? Have you ridden one of these bikes through a series of corners? You’ve mentioned that you had ridden an uncle or someone’s Sportster.
todd says
Yes, my father-in-law’s sporster with Buell heads and a bunch of other go fast work. I’ve also ridden a XB12R. I was not very impressed with the AMOUNT of power from either compared to the ZX12R I compared them to. The Kawasaki had more torque in the low RPM ranges and also had the benefit of a much higher rev ceiling if I wanted to. I rode the XB and the ZX through Redwood Rd in the East Bay hills, full of extreme twists and turns – not much room for top speed comparisons as if I cared the least.
I have never ridden a twin cam motor’d bike like the one Curt’s building. Looking at the spec sheets they still aren’t as powerful as the ZX even though they are a bit larger. Quite frankly, I can’t remember ever riding anything over 1200cc – I passed up a road test on the Rocket III when they first came out, maybe I should have given it a go.
I don’t care much for gobs of torque. It’s so easy to shift motorcycle transmissions (at least Japanese, Italian, and British ones) that I prefer a small capacity lightweight single when I am running through tight canyon roads. With a lightweight you don’t have to slow down much for the turns so accelleration out of them is not much of a factor. To me, huge torquey motors are really only suited for long distance travel.
It’s just a matter of preference.
-todd
hoyt says
spec sheets & more spec sheets.
Diesel says
I think everyone is missing the point. I’m sure even jap 600’s could give Curt’s bike a run for it’s money. But he want’s to ride something he built, with the engine he wants to run. Alot of you guys bust on every Harley powered bike that is shown here. Haters go ride your Busa’s and let some of us enjoy a custom AMERICAN bike for once.
curt winter says
Diesel, my thoughts exactly.
hoyt says
Diesel – Check out my blog that is dedicated to this concept. Hopefully that suggests I haven’t missed the point. This raises an interesting dialogue that the Kneeslider has brought up in the past …
The industry is most likely not willing to build a bike like the BTR because the “masses” are too busy citing spec sheets [see Todd’s comments above] and are not evaluating what is a great performance bike for the street.
Publications are largely to blame (cover story glorifying Yamaha’s inaccurate 17500 rpm inability). It was also interesting to read CW’s story about the HyperMotard. Matthew Miles asked Terblanche & the Project Engineer Sabbioni about the maximum rpm of the engine. They didn’t know & didn’t seem to care (there’s no redline on the gauge). The bike has usable power for the street throughout the gearbox, so the infatuation with rpm doesn’t exist, thankfully.
The article goes on to talk about how hardcore sportbikes “sell well because buyers have been told that it’s cool to be uncomfortable…” The author then asks, “But how do you alter the way people think?” Terblanche answered, “That’s your job, isn’t it?”
Unfortunately, the some publications have not given the type of exposure that definitively informs the public of a great trackbike vs. a great street bike. Why else are there hundreds of barely-used race replica bikes for sale mainly being sold by young, new motorcyclists?
Although the CW article was talking about comfortable ergos (low clip-ons vs. motocross style bars), the same arguments can be applied to power delivery. (b-t-w, I prefer reasonable clip-ons for my riding style and aesthetics)
Yamaha didn’t bring the MT-01 to the States for various reasons. I believe some of the reasons were reactions to the false, spec-citing, masses. That bike is too big in execution anyway. This leaves room for the BTR & Victory (on the mass produced front) to build this kind of bike.
todd says
I use the spec sheets to argue my point and confirm my suspicions. It is very hard to argue with cold hard data given off a dyno. You can argue ’till you’re blue in the face that your seat of the pants is a more accurate measuring tool.
I am picking on misgiven and outright erronious trains of thought: that a V-twin magically has more torque than a four cylinder of the same capacity.
This is very much the result of marketing hype from the likes of Harley, Dodge, and every other company that feels they have to justify their power outputs. I am so surprised that so many people have fallen into the trap. I too used to think that a Honda thumper dirt bike had lots of torque. I used to think that big V-twins had more torque. Then I rode these kinds of bikes and compared them to other kinds of bikes, back to back much like they do in the magazines.
I think the problem is that many (if not all) people here are comparing Harley’s biggest – and sometimes even bigger – engines with the smallest Super Sports bikes. This is an unfair comparison but it would tend to lend credence to your claims. Yes, a 1500cc motor will have more torque at low RPMs than a 600cc motor. Who can argue with that? And that’s the precise argument you are taking me to task for. What justification would anyone have for making those sort of comparisons?
I’ve never argued that the power delivery of a twin isn’t enjoyable or preferred by many people. I wouldn’t even dare to touch on matters of opinion like those. I myself prefer the sound and feel of a twin many times over that of a four but that isn’t the argument. Our posts have focused primarily on power output at given rpms and how that relates to a machine’s ability to go around a corner (or come out of one as being the case). I’ve found from person real-life experience that a 1200cc Kawasaki can accellerate out of a corner at 3500 rpm much stronger than a 1200cc Harley based twin can at any rpm. I think I phrased it as “twice as powerful”. This was a seat of the pants evaluation and I already stated above that isn’t the best measuring tool. I went home and looked up some numbers and posted them here.
I am not trying to attack anyone’s manhood simply because he rides a V-twin. Far be it from me, I ride a 500cc single.
-todd
hoyt says
No one has claimed an HD v-twin is more powerful than an inline 4 of the hayabusa-ilk. You brought up that subject. Back in the Wakan post, people discussed aftermarket v-twins such as the S&S 1640 & Curt’s Rev Tech 110 c.i. (triple digit torque figures if you want to discuss stats)
The angle many people have come from is the power delivery – the amount AND type of torque available at a low rpm. Re-read Paul’s “Accessible Performance” post.
You said, “I myself prefer the sound and feel of a twin many times over that of a four but that isn’t the argument”.
That is almost precisely the argument here and in the Wakan post. The feel of a twin translates to many rider’s ability & confidence to smoothly ride corner after corner. You still seem to be stuck in spec-sheet-land. The saddle evaluation is the better stick when discussing streetbikes.
It is no surprise to me that a skilled friend who used to be a handful to keep up with on the street (while riding a 750 Ducati) is not nearly as quick through the curves on his R1.
Bob Horn says
On the street, the seat of the pants dyno is the only one that counts. Dynos aren’t much fun to ride.
If you want to talk lap times, then spec sheets get even more useless. If specs mattered, then we could eliminate racing all together and just mail trophies to the guy with the highest peak dyno run! Wouldn’t that be FUN!!!!
A well known race car engineer once said “Horsepower sells engines, torque wins races”.
The dyno figures for a stock Harley engine are meaningless – there’s no such thing as a stock engine in a bike like this. They really wake up with very little work and money. It’s a power increase you can feel where it matters most on the street – at the seat of your pants.
Diesel says
I will never own a modern sport bike. I am 6’5 and 350 lbs. After 15 minutes I’m begging for a standard motorcycle. I am excited about the new wave of Supermoto style bikes as their geometry is suited for me and it’s a new and fun. I think KTM is making some exciting bikes, but in the back of my mind I wonder what it would be like to build a Vtwin supermoto style or even a Vtwin dualsport.
Hoyt, I dig the MT-03 and we’ll never see that either.
hoyt says
The MT-03 or the MT-01? The 03 might look like a pocket bike with someone your size, nonetheless, they are cool looking. I saw one in person in northern Italy.
If you’re interested, look up Curt – he’s built everything from race cars, choppers, hill climbers, to 250cc road racers, etc. A version of a BTR built with ergos like a Tuono would be easily adaptable.
todd says
OK, forget the spec sheets, I’ll never again bring up recorded data.
I’ve said it many times and people still argue against it: A Kawasaki 1200 (not even “tuned for torque”) pulls stronger, harder, smoother out of a corner at 3,500 RPM than a 1200 Harley. I’ve experienced it first hand, seat of the pants.
-todd
Paul Mc says
Curt,
Good luck on this project, I too can not understand why this has not been done correctly before. I know years back there was a company out of Switzerland who made some pretty crazy frames for shovelheads, but not since. I’ve been riding HD’s for the past 25 years, and have liked the motors but the suspension always sucked, and had to throw $$$ into them to make them work for me. Buell does not do it for me yet, but the Uly comes the closest.
I really think there is a market for a GS type of Dual Sport bike with a Big Twin EVO/Twincam, or x-wedge. Moto Guzzi is coming out with the Stelvio (i’ve been on that great pass) later this year, KTM has one, and BMW..Honda Africa Twin, and early Transalps are cool and others in Europe have them.
Please someone make one right here in the US of A!!
I’d sell both my current HD, and my R1200GS to get it!!
Paul
Curt Winter says
Paul, if what you want is a big twin powered dual sport, lets build one. I actually do more off road riding than anything else. I just did a ride that went from Reno to Vegas, it was 620 miles, off road the whole way and we did it in two days, me and 5 of my buddys, we plotted our own corse by way of googling earth and picking weigh points to enter into our gps. I’m building a bike right now that uses all the geometry and suspension components from a crf 450r and for power I’m using a Yamaha xt 600 motor that has been worked over. I know there not the biggest power maker, but they run strong, they lack radiators which is one less thing to break when your in the middle of nowhere. It should be a cool bike. If you would like to build something with a big twin let me know, I think that would be a neat bike.
Curt.