Tachometer info?

[Elding]

The thing is, if you have speedometer already on your bike and wanna put this tachometer on, the tachometer is going to interference with speedometer and you will have bulls**t numbers, not all the time tho, happens to me every 2 seconds or so. Maybe its more often when im riding faster. Im gonna fix that by adding shield cable to tachometer. I hope it will fix the problem.

To do with wraping the cable, everything above 5 times is alright.

 

[Whitewill1412]

Not smarty pants stuff. Basic algebra with a sprinkle of geometry.

A standard 4.1:1 primary reduction (20 tooth bevel and 82 tooth clutch gear - standard on most current 2 stroke cg engines) with a 10t drive and 44t driven on a 26 inch wheel means you will see 5812rpm when traveling at 25mph.

If your setup matches the above then you can wrap your wire, go 25mph via semi accurate speedo, and see if the tach reads around 5800rpm.

Thanks. It would have taken me all day to figure that out. You did it for me. You're awesome. If only I had you to copy off of in math class

 

[DAMIEN1307]

The thing is, if you have speedometer already on your bike and wanna put this tachometer on, the tachometer is going to interference with speedometer and you will have bulls**t numbers, not all the time tho, happens to me every 2 seconds or so. Maybe its more often when im riding faster. Im gonna fix that by adding shield cable to tachometer. I hope it will fix the problem.

To do with wraping the cable, everything above 5 times is alright.

You are probably running a Non-resistor spark plug...That is what normally interferes with speedometers and tachometers.

I had that problem of interference myself until I started using Resistor spark plugs only, now the electronics have no more RF interference or erroneous numbers being thrown out at me...lol.

 

[ImpulseRocket]

The whole kit and kaboodle...lol...lol.

My last name is not exactly Einstein when it comes to math formula's...lol.

Gear ratios multiply torque and divide rpm by the ratio. Since they multiply and divide, you also do the same for any subsequent gear ratio in the chain of the drive system. So the 4.1:1 ratio off the clutch gear is multiplied by the sprocket ratio. 4.1 x 4.4 = total gear reduction, which is 18.04:1

In a practical scenario let's say the engine makes 5lb-ft of torque at a peak rpm of 5000.

Since the ratio multiplies that torque and divides the rpm, at the drive sprocket on the motor (your 10 tooth) you would now have 20.5 lb-ft and the sprocket would turn at 1,219.5 rpm.

Take those figures and pass it through the 4.4:1 ratio of a 10 tooth drive and 44 tooth driven on the wheel, and you end up with 90.2lb-ft at 277.16 rpm at the wheel hub.

Or, since we already know the total gear reduction we can simply multiply and divide by 18.04.
5 x 18.04 = 90.2
5,000 ÷ 18.04 = 277.16

 

[Elding]

You are probably running a Non-resistor spark plug...That is what normally interferes with speedometers and tachometers.

I had that problem of interference myself until I started using Resistor spark plugs only, now the electronics have no more RF interference or erroneous numbersC being thrown out at me...lol.

I dont think sir. I have CR8HIX which has 5K ohm resistor. Yeah my speedometer give normal readings and then suddenly it jumps up to like 40 mph which is pretty weird if you are really going 25 XD

 

[Elding]

Gear ratios multiply torque and divide rpm by the ratio. Since they multiply and divide, you also do the same for any subsequent gear ratio in the chain of the drive system. So the 4.1:1 ratio off the clutch gear is multiplied by the sprocket ratio. 4.1 x 4.4 = total gear reduction, which is 18.04:1

In a practical scenario let's say the engine makes 5lb-ft of torque at a peak rpm of 5000.

Since the ratio multiplies that torque and divides the rpm, at the drive sprocket on the motor (your 10 tooth) you would now have 20.5 lb-ft and the sprocket would turn at 1,219.5 rpm.

Take those figures and pass it through the 4.4:1 ratio of a 10 tooth drive and 44 tooth driven on the wheel, and you end up with 90.2lb-ft at 277.16 rpm at the wheel hub.

Or, since we already know the total gear reduction we can simply multiply and divide by 18.04.
5 x 18.04 = 90.2
5 ÷ 18.04 = 277.16

I always wonder why engine makes peak torque at lower rpm than at high, I mean more volume more power nah?

 

[DAMIEN1307]

Gear ratios multiply torque and divide rpm by the ratio. Since they multiply and divide, you also do the same for any subsequent gear ratio in the chain of the drive system. So the 4.1:1 ratio off the clutch gear is multiplied by the sprocket ratio. 4.1 x 4.4 = total gear reduction, which is 18.04:1

In a practical scenario let's say the engine makes 5lb-ft of torque at a peak rpm of 5000.

Since the ratio multiplies that torque and divides the rpm, at the drive sprocket on the motor (your 10 tooth) you would now have 20.5 lb-ft and the sprocket would turn at 1,219.5 rpm.

Take those figures and pass it through the 4.4:1 ratio of a 10 tooth drive and 44 tooth driven on the wheel, and you end up with 90.2lb-ft at 277.16 rpm at the wheel hub.

Or, since we already know the total gear reduction we can simply multiply and divide by 18.04.
5 x 18.04 = 90.2
5,000 ÷ 18.04 = 277.16

Let's simplify this for me, the mathematically mentally impared old fart...lol.

Knowing that I have the stock P-85, with 26 inch mag rims, 26 X 1.75 tires front and back, stock 10 tooth drive gear in the front, 36 tooth drive gear in the rear, and custom cut chain for no tensioner...What does that mean for my build set-up???

What does the math say it should do, keeping in mind that I have had it up to 51 MPH just once and still had plenty of throttle left to go and didn't sound like it was even breaking a sweat doing it???...lol...lol.

 

[ImpulseRocket]

Let's simplify this for me, the mathematically mentally impared old fart...lol.

Knowing that I have the stock P-85, with 26 inch mag rims, 26 X 1.75 tires front and back, stock 10 tooth drive gear in the front, 36 tooth drive gear in the rear, and custom cut chain for no tensioner...What does that mean for my build set-up???

What does the math say it should do, keeping in mind that I have had it up to 51 MPH just once and still had plenty of throttle left to go and didn't sound like it was even breaking a sweat doing it???...lol...lol.

To go 51mph with a total gear reduction of 14.76 (4.1 x 3.6) you would have the engine cranking at around 9700rpm. There is some margin of error here, but by strict numbers, that's the reality.

Chain doesn't factor. Just the sprockets.

 

[DAMIEN1307]

engine cranking at around 9700rpm.

These Phantoms can actually rev that high???...I don't have a tach but it didn't seem to me it was revving up as high as this when I did it.

 

[ImpulseRocket]

These Phantoms can actually rev that high???...I don't have a tach but it didn't seem to me it was revving up as high as this when I did it.

Oh, yeah, they can manage the higher RPM no problem. The bottom ends probably won't last too long turning that fast, but the cylinder port timing figures can do it, no sweat.

My bike sits right at about 9000rpm to do 50 with my setup, and it can do it with enough space to stretch its legs. Since I am geared a bit taller overall thanks to my larger wheel diameter, and a bit of a large sail sat atop my bike, it probably struggles a bit more than it does with you on yours.

I spend 99% of my time around 5500 and 6500rpm and never going past 7000rpm. That keeps me between 30 to 35ish, and around 7k is about 40mph, or just shy of it. I don't even take my speedo with me much anymore. I have a.good idea of my speed based on my tach.