Just Installed A Tachometer On My R3T

Araz said:

This is a long read. Stems from the fact that i found tach installation somewhat tricky and decided to do math instead. I've done this because I didn't need tach as such, I needed to know optimal speed for each each gear range

Equation is simple > MPH = (Engine RPM * Radius) / (Final Gear Ratio * 168)

Triumph manual states following gear ratios:

1st 2.929
2nd 1.947
3rd 1.435
4th 1.16
5th 0.964
Primary Drive 1.034
Secondary Drive 1.043
Final Drive 2.846

Radius in the equation stands for the Tire Radius (not just wheel). Using tire size calculator, factory 180/70 R16 (rear) has a tire diameter of 25.9 inches, i.e the radius of 12.95 inches

Final Gear Ratio is the product of gear you are driving at and all the gears on the path to tire. So if you are travelling at 5th gear, Final Gear Ratio would be 5th * Primary * Secondary * Final = 0.964 * 1.034 * 1.043 * 2.846

There was a post earlier in the thread with a chart of RPM vs Speed (corrected mph values) at presumably the fifth gear (attachment 1). I used this chart as a QC to calculations, so i could then calculate speeds for other gears as well

To my surprise when i calculated speed for rpms used in said chart (att 1) the difference started creeping up to 5mph at 90mph and onwards (attachment 2 > speed on the chart vs calculated (as per manual) speed). I wasn't sure what started causing this diff since there shouldn't be uncertainties in tire radius and gear ratios..Nevertheless, I was decisive to match the calculated values, so I used 5th gear ratio, tire radius and rpm as known parameters, and solved for the product of primary, secondary and final drive ratios..resultant calculation was spot on (second rightmost column) with the numbers shown in the chart in att 1.

Finally, using the knowledge of identified true ratios, i have calculated the speed for all the remaining gears..

I you'd derestricted Touring with Power Tripps tune, your engine max RPM should increase from 4500 to 6000 rpm. Also, if you believe torque and hp lines from his chart (attachment 4) it probably would makes sense to change gears roughly at 5000 rpm(for best acceleration)..As per the chart in att 3, if you think that 5000 rpm is ok, gear changes should happen as following:

1st gear - 40mph
2nd gear - 60 mph
3rd gear - 80 mph
4th gear - 100 mph

Happy to hear any feedback and make adjustments where necessary

Click to expand...

Bedifferent said:

I know some of you R3T owners have talked about putting a tachometer on your bike. I've been looking and decided on the Koso BA035103 in chrome...It also comes in black. I spent most of the afternoon working on it, but I'm fussy. I used a Kuryakyn P-Clamp to get it mounted where I wanted it. I tied it into my center coil as it was the easiest to get to. A couple of adjustments and it seems to works fine from the get go. I'm posting this video. As you can see I didn't get it done till after dark. I'll post a few more shots tomorrow in the daylight after I get all the wires neatly dressed and everything buttoned up.

Well, I guess I can't post a video of it in action...I guess a picture or two will have to do for now.

[Add by @Joesmoe - with permission]

The tachometer has four wires, three in one group and one separate. The three 22ga wires are power-switched; power-unswitched, and ground. There is a long single wire, and this is for the pulse. I tied the switched wire into the position light that was in the headlight shell before the LED conversion. I ran a new wire for unswitched back to the auxiliary distribution panel under the seat between the rear fender and battery. The tachometer default count setting is one cylinder, and this is what works on the Rocket. Physically, the tachometer has two small buttons on the bottom, and if one looks closely with good eyes or a magnifying glass, one can see labels "SELECT" (left) and "ADJUST" (right). Having hooked up the sense wire (long blue) using the supplied pigtail (they call it "RPM Wire (Type B)") to the middle coil as described above, must be changed to "Lo". So there are three settings available on the tachometer, in this order: 1) Number of pistons; 2) Hi-Lo sense; 3) backlight brightness setting.
To enter the set mode, with power on the tachometer, push both buttons and hold for three seconds, and you will see the hand of the tachometer move to 500. This is the default setting of one spark for each two revolutions of the engine, and what works on the Rocket Touring. So leave that as is, and press the "SELECT" button once to change to the sense setting. Press the "ADJUST" button once. This should change from the default "Hi" to "Lo". You're done with settings, so push and hold the "SELECT" button to put the tachometer back into the operating mode.

If for some reason, the tachometer is still not reading, repeat the steps above.

Click to expand...

Tripps said:

If I'm running wide open I shift at 8000, but sometimes it gets there so fast I forget to shift in time. I looked down once and saw 9200 on the overrun. Stock crank and bearings.

Click to expand...

Araz said:

@Tripps, is this engine capable of running this fast? I assume it is far away from being stock?

Click to expand...