No sh!t, ill buy one myself and dive into the engine and tranny, bet i could push it to 40bhp from that… but i dont believe it, thats over a 100bhp per litre from a scooter engine.
This ladys and gentlemen is a TUNED honda crf250 motocross bike, it uses alot of F1 technology in its piston design and a very advanced single cam 4 valve head.
and with that i think we can safely be assured that 30bhp from a 300cc scooter engine is nigh on impossible.
Manufacturers measure power at specially extended cranks on a test bench with a blueprinted engine, chilled oxygen rich air bottled below sea level and race fuel don’t they?
I’ve seen a dyno printout for a CPI and it had about 14kw as standard, which I think is about 19hp. I’ll try to find it.
Realistically you can get 10bhp per 100cc from a normal 4 stroke can’t you? The Ninja 250 has 32bhp according to Kawasaki, the Yamaha WR250x motard is meant to have 28 so 30 from 300cc isn’t stretching the bounds of imagination that much. Is it?
In crankshaft hp terms, Moto GP engines make around 20 hp per 100cc. “R” and “RR” stock liter bikes make around 15 hp per 100cc. With small displacement engines, as you mentioned, it’s possible to approach the liter bike ratio. My incredulity is whether Kymco, in a scooter, has an engine at the level of the best JP bikes. I don’t think so, based on all their other engines… but of course, they could have taken a “Taiwanese license” from one of the big 4.
[quote=“jaame”]
Realistically you can get 10bhp per 100cc from a normal 4 stroke can’t you? The Ninja 250 has 32bhp according to Kawasaki, the Yamaha WR250x motard is meant to have 28 so 30 from 300cc isn’t stretching the bounds of imagination that much. Is it?[/quote]
Yes it’s possible. Is it practical in a scooter? Not really.
Think of a 300cc single as 1/4 of a 1200cc four. Then look at the 1200 fours that are out there now with four times the claimed power of this Kymco. Most motors in that class make peak torque around 8,000rpm and peak power around 10,000rpm. The WR250X you mention also makes it’s peaks in this range.
Would most people want a scooter that didn’t come on cam until 6 or 7,000rpm? Remember for a moment that this scooter is not going to be a mere 1/4 of the weight of that 1200… more like somewhere between 1/2 and 3/4 of that.
With a CVT transmission it would take an almost intolerable time to wind up the engine before the automatic clutch started to lock up. Stop and start traffic would be horrible. Scooter engines need to be tuned for midrange torque… something that rules out supersport volumetric efficiency, at least with current naturally-aspirated technology.
[quote=“redwagon”][quote=“jaame”]
Realistically you can get 10bhp per 100cc from a normal 4 stroke can’t you? The Ninja 250 has 32bhp according to Kawasaki, the Yamaha WR250x motard is meant to have 28 so 30 from 300cc isn’t stretching the bounds of imagination that much. Is it?[/quote]
Yes it’s possible. Is it practical in a scooter? Not really.
Think of a 300cc single as 1/4 of a 1200cc four. Then look at the 1200 fours that are out there now with four times the claimed power of this Kymco. Most motors in that class make peak torque around 8,000rpm and peak power around 10,000rpm. The WR250X you mention also makes it’s peaks in this range.
Would most people want a scooter that didn’t come on cam until 6 or 7,000rpm? Remember for a moment that this scooter is not going to be a mere 1/4 of the weight of that 1200… more like somewhere between 1/2 and 3/4 of that.
With a CVT transmission it would take an almost intolerable time to wind up the engine before the automatic clutch started to lock up. Stop and start traffic would be horrible. Scooter engines need to be tuned for midrange torque… something that rules out supersport volumetric efficiency, at least with current naturally-aspirated technology.[/quote]
Yep, scoots are tuned for low rpm torque, not 12,000rpm+ peak power bands and thus will not make the high power you want it to.
im saying 20bhp is about right for this engine.
I finally put it today on the dynometer. These that they’ve told me and wrote in this post proved wrong or at least the numbers I wrote didn’t refer to wheel power but to engine power. I’m very sorry for the false data.
The result on the dyno run for the Kymco Downtown is 24ps on wheel. This is a very good result for a 300cc scooter, the second stronger scooter at 300cc the Honda SH300 on the dyno hits 20ps on wheel. Also it can be compared with 400cc scooters, for example the Suzuki Burgman 400 hits 24,5ps on the wheel.
The Downtown 300i has the strongest motor in its category available today. Well done Kymco!
Where is the torque peak, in rpm? Broad peak? Any chance of a graph?
Here is the plot. Note that this isn’t a good measurement because the rear tyre has a problem and the scooter was bumping on the dyno (this is why there are so many bumps on the graph). Also note that this dyno is said to be “pessimistic”.
The mini-site and the factory page for the Kymco Downtown 300i are online (on the latter page, scroll to 300cc, click on Downtown). Italian designer. Goal is to unseat the Honda SH 300, SH 150, and SH 125 as the three top scooters sold in Italy. The Downtown series is 300cc, 200cc, and 125cc (Specs table in the mini-site). The Honda SH series were also Italian designed… and used Honda MX engine designs. Nothing confirmed yet on the rumor (see next link below) that the 300i 4-valve EFI engine design came from BMW. It appears that the both frame and engine are new AND that the hp claim may be real (at the crankshaft).
One poster in this Kymco forum says the Downtown series is a collaboration with BMW. So, the rumor is that the engine design came from the munchkins in München.
The expectation is that the Downtown series will clobber the Honda SH series. Storage in the Downtown 300i is TWO full face helmets under the seat. The SH cannot store a single helmet under the seat.
It will be sold in the States, EU, not sure about Oz. It would be so like Kymco not to release it in the 'wan.
Updated spec from Kymco for the “production model” of the 300i:
MAX.HORSEPOWER ENGINE (ps/rpm) / kw(r/min)
29.5/8500 (ps/rpm) , 22.0/8500 (kw/rpm)
So, 29 HP at the end of the crank, and then of course you have to push that through the wonder of loss and friction that is a scooter CV transmission, losing 30-40%.
final value: 21 HP at best.
True, but still the most powerful 300cc scooter engine on the market by a significant amount, more than Aprilia, Piaggio, Vespa, SYM, Honda, etc.
Kinda disingenuous when Honda’s CBR250RR puts out more than 40 HP.
… from four cylinders. Apples and oranges?
Scooter, llary, this is a scooter not a Super 4 or Ninja 250.
Doesnt the vespa GTS250 but over 20bhp down… thats been out for about 3 years now.
pardon my ignorance but @ 20ish wheel horsepower… who cares? that’s a power to weight ratio that’s worse than a 4-cylinder econobox car. even at 30whp, we’re still talking about entry-level family sedan levels of power-to-weight ratio.
then again, i never fully understood why people would tune fwd hondas until a buddy of mine showed me his na 240whp k20 swapped, 1850lb eg hatch. but i don’t think anywhere near that equivalent is achievable with a scooter unless we’re talking about something like a TMAX.
nothing againsts scooter, because they serve the purpose of urban transportation infinitely better than say a cbr250, but i am confused as to why people would choose to tune on such a platform.
[quote=“mabagal”]pardon my ignorance but @ 20ish wheel horsepower… who cares? that’s a power to weight ratio that’s worse than a 4-cylinder econobox car. even at 30whp, we’re still talking about entry-level family sedan levels of power-to-weight ratio.
then again, i never fully understood why people would tune fwd hondas until a buddy of mine showed me his na 240whp k20 swapped, 1850lb eg hatch. but I don’t think anywhere near that equivalent is achievable with a scooter unless we’re talking about something like a TMAX.
nothing againsts scooter, because they serve the purpose of urban transportation infinitely better than say a cbr250, but I am confused as to why people would choose to tune on such a platform.[/quote]
Those RS100’s and cygnus’s with 200cc+ engines are a right giggle to ride, try it and let get back to me.
ITs different from almost anything else you have ever ridden.
sbl, is it true that the 125cc four-stroke BWS (stateside, “Zuma”) engine is a bolt-for-bolt swap for the 50cc two-stroke BWS engine? If I understand this mod, just the engine is swapped, but it seems to me that the variator and other CVT parts might be stronger for the 125cc, so wouldn’t the swap include the CVT? I’m thinking of doing this mod stateside, where there are plenty of both models around.
I’m told by a Zuma tuner here that the only downside is that the starter from the 50cc unit won’t work… kick start only after the mod.
Of course, if the swap is possible, the 125cc could be rebuilt with a 171cc kit (or already rebuilt before the swap). 
mabagal, your power to weight comparison between a scooter and a car is way off. I don’t have to get a calculator out to know that a 200kg/20hp scooter has a better power to weight ratio than a 1600kg/100hp car.
I can understand Kymco claiming that a 300cc scooter makes 30hp. All the scooter companies make similar claims of almost 10hp per 100cc for their 4v headed scooters. Sports bikes make their power high in the rev range (CBR250 42hp @ 16000-odd rpm I seem to remember) but that’s a lot more than 10hp/100cc. Almost double in fact. Looking at scooters in Taiwan tells a similar tale of almost 10hp/100cc.
SYM Fighter 150 claimed 13hp from 149.6cc
Yamaha Cygnus claimed 11.9hp from 124cc
Kymco Racing 150 claimed 14hp from 150cc
I want to put my CPI on a dyno. Does anyone know of a place that has a dyno in Taoyuan? How much?