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Post by ThomasTPFL on Dec 6, 2018 0:23:38 GMT -5
Those guys were running over 100 mph on 50cc. Yes they had manual gearboxes, but what else is keeping us from seeing those speeds from 50cc two stroke scooters and mopeds?
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Post by benji on Dec 6, 2018 2:10:25 GMT -5
they had manual gearboxes some had 14 speeds to help keep them in power band. |
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Post by tiny on Dec 6, 2018 7:51:02 GMT -5
Thats it really. Just the gear box. Give a 50cc scooter a 3-4 speed gearbox and it would go way faster then with a CVT.
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Post by 190mech on Dec 6, 2018 8:24:49 GMT -5
Super skinny tires and a 95 pound rider!!
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Post by aeroxbud on Dec 6, 2018 12:11:09 GMT -5
Super skinny tires and a 95 pound rider!! And a rebuild after every race! |
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Post by fuzzyruttin on Dec 6, 2018 12:19:23 GMT -5
I don't know what kind of budgets they had back then, considering the top-end motoGP bikes are $1M prototypes these days. Money makes things go faster.
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Post by 190mech on Dec 6, 2018 12:51:22 GMT -5
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Post by Lucass2T on Dec 6, 2018 14:38:52 GMT -5
Yeah jamathi is the perfect example. Three dudes building a racer from scratch. Those engines were boxy af just for manufacturing convience.
To get to those speeds its not just sheer power but streamlining, reducing drag and every form of resistance and think through every single part.
A good start would be an aprilia rs50, derbi gpr or motorhispania rx kinda bike.
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Post by snaker on Dec 6, 2018 15:09:37 GMT -5
What a great article. I don't really think that having the lots-o-gears transmissions was so much a advantage as it was a necessity to keep on top of a tiny power band. All that extra shifting can take away from performance because acceleration would stop during a shift. Plus it keeps the rider very busy. A perfect CVT has an advantage in that area because there is no pause in upshifting. Of course manual transmissions outperform cvt's in other area's. I think its all about the engine. This article seemed to say that the relatively same engine was putting out between 6-19 hp with different versions if I read it right. Playing with water cooling, rotary valve's, etc makes a huge difference. And then you add tuned exhaust's. Whole different story. The reason why independents could out perform factories at times was because factories of the day didn't really have a clue about the 2 stroke mystery's either. Early snowmobile 2 stroke engines were designed for industrial use in pumps and washing machines. They had no power advantage's. Just cheaper, lighter and were easier to pull start in cold weather. Even when the factory put out a "hot rod" model, they would often put on a "megaphone" exhaust which was a short straight pipe with no internals. The only thing performance was a hellacious noise and unburned fuel spewing out. A 600cc engine from the mid 70's may of had 60 hp. A current 600cc is pushing 125 hp, that's reliable hp. A good example of the range of power of the 2 stroke.
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Post by benji on Dec 6, 2018 21:27:30 GMT -5
A lot of these old 50ccc GP race bikes had multiple cylinders, and would hit RPMs upwards of twenty thousand.
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Post by benji on Dec 6, 2018 21:29:18 GMT -5
I'm part of a 2t r&d group on Facebook with Jan thiel and ferry brouwer. Lots of cool stuff posted on there. |
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Post by benji on Dec 6, 2018 21:54:18 GMT -5
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Post by ThomasTPFL on Dec 6, 2018 22:48:43 GMT -5
My understanding is that rotary valves are actually more efficient than reed valves at specific range, reeds make it easier to widen the powerband.
I get the rebuilding every race part, but following some folks on forums it seems the guys seriously chasing big numbers aren’t keeping engines together for more than a few hundred miles anyway, either due to critical failure or just changing the build for more power.
I have seen video of some of those early bikes running where the rider isn’t able to get up to balancing speeds until he’s in third or fourth gear, so definitely engines tuned for high end .
Just throwing out my observations there.
I’ve been dwelling on it as I’ve been wanting to build a gp inspired bike for a while.
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Post by SMALL CC TEK on Dec 6, 2018 23:05:22 GMT -5
If your scooter had a gearbox and a you could change cogs , it would be called a motorcycle ! lol Seriously if it had all that your scooter would do 80 mph and a rotary valve would be nice I had a 76 KX 125 with one and the Mid to Top power was crazy ...
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Post by benji on Dec 7, 2018 10:42:03 GMT -5
If your scooter had a gearbox and a you could change cogs , it would be called a motorcycle ! lol Seriously if it had all that your scooter would do 80 mph Vespas have a gearbox and clutch. And I think 80 is actually achievable on one. I think they're 4 speed. And they're definitely scooters |
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