Homie was right!!! 13g better than 12g rollers!

[ScooterMan]

12g vs 13g rollers...that is the question!

Well, I got curious. Seeing as peak HP arrives at 8200rpm, and Homie was hitting 7400 RPM with 13g rollers (albeit with larger tires) I decided to order some 12g rollers and see for myself.

Did some 0-50 runs and compared them to my video of my timed 0-60 run with the 13g and the concensus is they're the same!!! And yet, it doesn't wheelie as easy with the 12g rollers. So, considering they have the identical time to 50, might as well keep the revs lower for engine longevity, and less chance of overheating due to the engine revving higher at the same speeds than with the 13g's. Here's my thought...

Yes, max HP is at 8200rpm, but max tq is undoubtedly lower by about 1700rpm if I had to guess. So, maybe instead of aiming for 8200rpm (the hp peak) we should be aiming mid way between the HP and tq peaks which would make that 7350RPM! Would be nice to see a graph showing tq, not just hp so I don't have to guess. Anyway, seems 13g is the sweet spot putting the motor between the HP and TQ peaks allowing it to launch hard yet pull strongly as possible, while keeping the revs as low as possible to achieve this result.

Ok, discuss if you need to!:geek:

Also, did the swap without pulling the bodywork for the first time. =)

[SECoda]

Well I have the 13's sitting in the drawer along side the Variator and face plate.

See how my font color matches the bikes colors? My wife made fun of it.

[yak]

Your mention of "wheelies" reminds me of a video with a guy doing spins and loops and wheelies on his scooter. He treated that scooter like a skateboard. It was on a tv show... i don't have a link.

[homie]

ScooterMan .... I don't know half the stuff you talk about but I am ONE with all my machines I was not impressed with the lighter rollers and I felt it. I would like to boast about that but the next header would be 'Homie was wrong'. So I will just not and let the force be with me

[SmellyTofu]

Your mention of "wheelies" reminds me of a video with a guy doing spins and loops and wheelies on his scooter. He treated that scooter like a skateboard. It was on a tv show... i don't have a link.

[Steph]

@Smellytofu - That is one on my fav PCX videos!

[sendler2112]

Not sure why it would pull a wheelie any better one way or the other with different weights since the engine is at a lower rpm to begin with when you yank it. But rear wheel torque is always the highest for any given speed when the engine is at the rpm of the power peak, not the torque peak, because the gearing multiplication of any transmission at the higher rpm power peak more than makes up for the slightly lower torque. We had a good engineering discussion about this at CBR250.net. Try your timed runs again. My timed runs, and weighted hill climb, improved with the pulling rpm at 8,000.
.

[sendler2112]

A good discussion of torque vs horsepower erupted here:
.
http://www.cbr250.net/forum/cbr250-perf ... alf-2.html
.
Too bad CBR250.net decided to erase all my photos in it's dying days which showed some of the charts.

[homie]

A good discussion of torque vs horsepower erupted here:
http://www.cbr250.net/forum/cbr250-perf ... alf-2.html
Too bad CBR250.net decided to erase all my photos in it's dying days which showed some of the charts.

how does a forum die and why did they go to the trouble to dump images?

[Pcxdemon]

Not sure why it would pull a wheelie any better one way or the other with different weights since the engine is at a lower rpm to begin with when you yank it. But rear wheel torque is always the highest for any given speed when the engine is at the rpm of the power peak, not the torque peak, because the gearing multiplication of any transmission at the higher rpm power peak more than makes up for the slightly lower torque. We had a good engineering discussion about this at CBR250.net. Try your timed runs again. My timed runs, and weighted hill climb, improved with the pulling rpm at 8,000.
.

Ditto!
Also setting your rpm for 8k does not mean your engine will work harder all the time. Infact it will still cruise same speeds with same rpm but on full throttle it will punch out to 8k for max performance, just imagine having an extra gear or two ratio going from 3sp gearbox to a 5sp gearbox.
Of course going too light and beyond 8k rpm with weights will have negative results top speed only as it will redline before it tops out max v..8k is a magic number.

[sendler2112]

how does a forum die and why did they go to the trouble to dump images?

It was a new model and was a great deal taking over for the venerable Ninja250 with more low end power and fuel injection and great fuel economy. So the forum grew rapidly to 1,400 active members and 3-400 logged on at any average time. It was interesting how many middle aged engineers were attracted by this bike. But lately it is about 1/10 the traffic it once had for a variety of reasons. Mostly because it seems that most everything had been said. Why they would dump our photos, I have no idea because there was some great stuff archived there. Maybe they wanted the space for the new CBR300R forum that they split off. They should have left it together on the 250 site as it is the exact same bike with just a different nose and a longer stroke.

[nribeiro]

Not sure why it would pull a wheelie any better one way or the other with different weights since the engine is at a lower rpm to begin with when you yank it. But rear wheel torque is always the highest for any given speed when the engine is at the rpm of the power peak, not the torque peak, because the gearing multiplication of any transmission at the higher rpm power peak more than makes up for the slightly lower torque. We had a good engineering discussion about this at CBR250.net. Try your timed runs again. My timed runs, and weighted hill climb, improved with the pulling rpm at 8,000.
.

Ditto!
Also setting your rpm for 8k does not mean your engine will work harder all the time. Infact it will still cruise same speeds with same rpm but on full throttle it will punch out to 8k for max performance, just imagine having an extra gear or two ratio going from 3sp gearbox to a 5sp gearbox.
Of course going too light and beyond 8k rpm with weights will have negative results top speed only as it will redline before it tops out max v..8k is a magic number.

Agreed!! In this moment I have JCosta vario instead of 12gr Dr. Pulley on stock vario and I have better acceleration of the line but on flats it's worst since the rev's at 100kph are at 9100 or more!!!

With 12gr sliders I'm around 8040 or litle more and it seems that keeps more speed with wind etc etc... Up hill's with sliders are better too.

I will try 14.50gr or 13gr... I have to test.

[sendler2112]

9,100 rpm at 100 kph would be normal for the stock vario also. And you would experience that rpm vs speed regardless of any reasonable selection of weights. Once the rpm goes greater than the pulling rpm of the weights, 8,000 rpm for instance, the weights are locked all the way out and have no further activity.

[nribeiro]

Disagree sendler2112. I'm not an expert but what I can see in the tacho is: stock vario with Pulley sliders at 100 I'm around 8040 rpm at full throttle.

[sendler2112]

Something is weird there because the original PCX125 was limited to 100kph for Euro A1 licensing and this was accomplished by a rev limiter at 9,200.

[Pcxdemon]

Disagree sendler2112. I'm not an expert but what I can see in the tacho is: stock vario with Pulley sliders at 100 I'm around 8040 rpm at full throttle.

I think sendler meant stock vario and rollers...makes sense as top speed is only 108kmh at 9300 stock pcx

[sendler2112]

With rollers or sliders. Either way. The rpm should be about 9,200 at 100 kph. If you change the vario to something like the NCY which has been machined out to give taller gearing, the rpm will be less.

[homie]

With rollers or sliders. Either way. The rpm should be about 9,200 at 100 kph. If you change the vario to something like the NCY which has been machined out to give taller gearing, the rpm will be less.

ie... that "crazy long gearing" you said was me

[sendler2112]

Crazy long gearing in a good way. I am going to order an NCY variator as soon as they get the NCY drive face back in stock.

[DeaninMilwaukee]

With the nyc drive face can you still use Dr pulley sliders, or is that not a good idea?