Well explained. For instance, I once owned a short stroke (CCM crank), BSA B50 500 four stroke. I often beat 400cc two strokes in Australian Dirt Track just with traction.
They look like an XR 400 or 650 motor to me. I never even heard of Rotax till I got into flat track. I like what I see being I'm a big fan of air cool Honda singles.
The channel is awesome. The torque curve explanation, well that wasn't so awesome. I would like to add this explanation about the torque curve. The 450 and "Sweet Rotax" have similar power curves, in that the power stroke is 720 degrees. Making for 1 big pulse every 720 degrees. The big "FlyWheel" effect could be added to any bike engine. What we are really after is a continuous power curve. Twin engines that fire at 360 degrees have a 100 percent better continuous power curve. There is a real good channel in here called "tech ingredients" where this subject was covered. He built a 4 cylinder engine from modifying chainsaw engines to create a light weight continuous power source. The continuous power delivery was efficient enough to power all the electric motors for the Drone he built.
When you say "What we are really after is a continuous power curve", and go on to say that a 360 degree firing twin has a 100% better continuous power curve... I assume you don't mean people racing dirt track motorcycles, as the we. People racing twin cylinder motorcycles in dirt track have often (historically) resorted to re-arranging camshaft lobes (and sometimes crankshaft) orientation, to fire both cylinders at or near the SAME time... Which of course puts one power pulse into 720 degrees, exactly like a single. Notice I said pulse, and not curve. The number of firing pulses per rotation has nothing to do with what most people call a "Power Curve". Normally a power curve is expressed as lines on a dyno chart, for each torque and horsepower. The video was surely played here in slow motion with sound, to dramatize the bang... bang... bang... bang of the Rotax hooking up to the dirt. A 720 degree firing interval is part of what makes that happen. The other virtually Rotax part of that excellent traction is it's huge moment-of-inertia, that comes not only from the engine's heavy crankshaft, but from that crankshaft's large diameter. This moment of inertia dampens each of the bangs from the cylinder firing, actually keeping it from ripping the tire out of contact with the track surface. 450 MX bikes have a crankshaft that's both lighter and smaller in diameter than the Rotax. The comparison of the Rotax part being 62% heaver, actually greatly understates it's advantage in moment-of-inertia. The Rotax's MOM advantage is more than likely 200% greater, when compared to a 450 MX/DTX engine. That advantage is also what helps the torque and horsepower curves on the (Dynojet type) dyno linger, longer than what mathematical power calculation would otherwise have it. When you say "The big "FlyWheel" effect could be added to any bike engine", you're a bit correct... but only in the most abstract sense. The reality of the situation, is that very few engines have the crankcase volume to fit a larger diameter crankshaft. In fact, I can't think of any modern ones that do. Fitting a large diameter flywheel somewhere else in/on the engine, is also almost always the devils errand. I speak to you of that, with a tremendous amount of hands-on experience.
@@chuckfry1227 Basically, yes. It moves the point where you are in rev range down, which can delay where the power "hits" or ramps up. This can soften wheelspin in some case.
Oversimplification: The sanctioning body at the time (AMA Pro or AMA Pro Racing, I tend to forget what the exact name version they were using) wanted factory involvement for single cylinder machines. The thought was to get them interested, framed flat track bikes needed to go. That forced the switch to motocross based "DTX" bikes. I don't think there was much factory involvement at the time of the rule change though.
@@FlatTrackFactory so money they were money hungry and pushed the privateer out so now the only thing we can race or afford is outlaw tracks thanks for the info mike👍
Old school Flat Track. Love it 👍🏻😎
Brilliant description of experience...
Thanks a lot 😊. I appreciate you taking the time to comment. Cheers!
I've been riding my Harley MT500 Rotax to work for 4 years, reliable and fun!
Right on!
Had an ATK406 with a Rotax! Unbreakable motor
Really enjoyed this video. Great explanation for a complex topic.
Glad you enjoyed it! Thanks for saying so.
Very interesting 👍
Great analysis of rotating mass along with grunt rather than rev's
Glad you liked it!
Well explained. For instance, I once owned a short stroke (CCM crank), BSA B50 500 four stroke. I often beat 400cc two strokes in Australian Dirt Track just with traction.
Yaaaassssss.
More please 😚
They look like an XR 400 or 650 motor to me. I never even heard of Rotax till I got into flat track. I like what I see being I'm a big fan of air cool Honda singles.
The Rotax has a classic and unique look, for sure. The timing belt cover makes it stand out, IMO. Cheers!
Got some interesting conversation on this topic for you this afternoon
Looking forward to it!
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The channel is awesome. The torque curve explanation, well that wasn't so awesome. I would like to add this explanation about the torque curve.
The 450 and "Sweet Rotax" have similar power curves, in that the power stroke is 720 degrees. Making for 1 big pulse every 720 degrees. The big "FlyWheel" effect could be added to any bike engine. What we are really after is a continuous power curve.
Twin engines that fire at 360 degrees have a 100 percent better continuous power curve.
There is a real good channel in here called "tech ingredients" where this subject was covered. He built a 4 cylinder engine from modifying chainsaw engines to create a light weight continuous power source. The continuous power delivery was efficient enough to power all the electric motors for the Drone he built.
When you say "What we are really after is a continuous power curve", and go on to say that a 360 degree firing twin has a 100% better continuous power curve... I assume you don't mean people racing dirt track motorcycles, as the we. People racing twin cylinder motorcycles in dirt track have often (historically) resorted to re-arranging camshaft lobes (and sometimes crankshaft) orientation, to fire both cylinders at or near the SAME time... Which of course puts one power pulse into 720 degrees, exactly like a single. Notice I said pulse, and not curve. The number of firing pulses per rotation has nothing to do with what most people call a "Power Curve". Normally a power curve is expressed as lines on a dyno chart, for each torque and horsepower. The video was surely played here in slow motion with sound, to dramatize the bang... bang... bang... bang of the Rotax hooking up to the dirt. A 720 degree firing interval is part of what makes that happen. The other virtually Rotax part of that excellent traction is it's huge moment-of-inertia, that comes not only from the engine's heavy crankshaft, but from that crankshaft's large diameter. This moment of inertia dampens each of the bangs from the cylinder firing, actually keeping it from ripping the tire out of contact with the track surface. 450 MX bikes have a crankshaft that's both lighter and smaller in diameter than the Rotax. The comparison of the Rotax part being 62% heaver, actually greatly understates it's advantage in moment-of-inertia. The Rotax's MOM advantage is more than likely 200% greater, when compared to a 450 MX/DTX engine. That advantage is also what helps the torque and horsepower curves on the (Dynojet type) dyno linger, longer than what mathematical power calculation would otherwise have it.
When you say "The big "FlyWheel" effect could be added to any bike engine", you're a bit correct... but only in the most abstract sense. The reality of the situation, is that very few engines have the crankcase volume to fit a larger diameter crankshaft. In fact, I can't think of any modern ones that do. Fitting a large diameter flywheel somewhere else in/on the engine, is also almost always the devils errand. I speak to you of that, with a tremendous amount of hands-on experience.
Fantastic explanation! Way better than a dumb m/c racer like me!
For you lurkers: Alan builds race engines. For a living. And they win. Nationals. We're lucky he took the time to comment.
Wish I could hear you talk about how the Rotax crankshaft compares to the old BSA Goldstar 500 crankshaft.
Soooo, I've heard it in your videos, .. what the rev. limiter set at on your bike?
Depends. 7700-8600 depending on all the sneaky things, that things that depend on, depend on. :)
Torque is king.
Get on with it!
I do have an Aprilia with Rotax engine, Tuareg , from the 80s not the new one!
12 lbs, but that rod looks long as well.....
A wide, flat torque curve doesn’t suck.
Do you go faster when you over-rev a rotax?
I don’t. When I was a kid, Ron Wood told me to, “Drop a tooth. You will go faster”.
@@FlatTrackFactory are you saying drop a tooth on the rear so the torque isn’t so abrupt?
@@chuckfry1227 Basically, yes. It moves the point where you are in rev range down, which can delay where the power "hits" or ramps up. This can soften wheelspin in some case.
@@FlatTrackFactory thank you for the response I wasn’t quite sure
Got a "like new" XR500 "Harley" in a Boss frame sitting here doing nothing.
Why did ama " outlaw" the big nasty rotax?
Oversimplification: The sanctioning body at the time (AMA Pro or AMA Pro Racing, I tend to forget what the exact name version they were using) wanted factory involvement for single cylinder machines. The thought was to get them interested, framed flat track bikes needed to go. That forced the switch to motocross based "DTX" bikes. I don't think there was much factory involvement at the time of the rule change though.
@@FlatTrackFactory so money they were money hungry and pushed the privateer out so now the only thing we can race or afford is outlaw tracks thanks for the info mike👍
@@brooksstevenson8358 plus they had a nasty habit of beating the XR750 on a lot of half miles👍 good video.
600cc helps too
Doesn't hurt!