Open query!

[Carlo Guzzi]

Hi guys,
I have an MMB Tach that needs 'tuning' via the potentiometer.
So I need to know (for all those that ride a '98 EV Cali) revs versus speed
i.e. what revs is she turning when she's running at 60mph, 80mph, 100mph.
Simple but, oh so essential!
Thanks in anticipation.

 

[john zibell]

It might be more accurate to connect to diagnostic software. The software will read the RPM via the ECU. Then you could calibrate the tachometer to match the software reading. It would be more accurate than trying to judge by the speedometer.

 

[Carlo Guzzi]

It might be more accurate to connect to diagnostic software. The software will read the RPM via the ECU. Then you could calibrate the tachometer to match the software reading. It would be more accurate than trying to judge by the speedometer.

Thanks John, appreciate that but I forgot to mention that this is a de-electronified EV i.e. no EFI or computer just old fashioned carbs and CDI. So, I need actiual readings I suppose.

 

[Dinsdale Piranha]

Speedos are deliberately calibrated to be optimistic - they read high! That's so that you can't blame the speedo manufacturer for your speeding tickets. In Oz the Australian Design Regulations (ADRs) require speedos to be within +10%-0% of actual speed. Your actual speed vs your indicated speed is dependent on factors like: tyre size, tread pattern, tyre wear, tyre inflation, load on the bike and prolly a few minor factors I can't think of right now. That's not to mention where in the +10%-0% your individual instrument lies. Note that that's a %age of actual speed. eg at an actual 100Km/h you speedo could well read (indicated) 110Km/h or even worse if you've played with tyre sizes or haven't pumped them up for a while.

A GPS (even an el cheapo automotive one) should give you something in the order of +-0.5% with good satellite coverage.

Tachos, on the other hand, can be and usually are calibrated quite accurately. Modern mass-production methods can easily give you +-2%. Trying to use a less accurate instrument to calibrate a more accurate instrument just isn't going to happen, except by accident! There are calibration instruments which will take an input from your ign coil or HT lead or CDI output and give you an accurate reading (within the order of +-0.5%). You can even get add-ons for many digital multimeters which will do the same for you. I doubt that you ave access to a small portable CRO, but that's what I use.

If you can get a very accurate idea of your speed then you can do the maths and work out what rpm you should be doing at what speed. Apart from a table of gear ratios (including primary drive and final drive ratios) you'll need to measure the diameter of the wheel from where your speed is being read (front or rear) to within about 1mm. The more accurate the better with this measurement coz each step from here magnifies any measurement error. Do this with the bike loaded for most typical riding. Then convert that to a rolling circumference. It's basic arithmetic from there.

 

[Carlo Guzzi]

Speedos are deliberately calibrated to be optimistic - they read high! That's so that you can't blame the speedo manufacturer for your speeding tickets. In Oz the Australian Design Regulations (ADRs) require speedos to be within +10%-0% of actual speed. Your actual speed vs your indicated speed is dependent on factors like: tyre size, tread pattern, tyre wear, tyre inflation, load on the bike and prolly a few minor factors I can't think of right now. That's not to mention where in the +10%-0% your individual instrument lies. Note that that's a %age of actual speed. eg at an actual 100Km/h you speedo could well read (indicated) 110Km/h or even worse if you've played with tyre sizes or haven't pumped them up for a while.

A GPS (even an el cheapo automotive one) should give you something in the order of +-0.5% with good satellite coverage.

Tachos, on the other hand, can be and usually are calibrated quite accurately. Modern mass-production methods can easily give you +-2%. Trying to use a less accurate instrument to calibrate a more accurate instrument just isn't going to happen, except by accident! There are calibration instruments which will take an input from your ign coil or HT lead or CDI output and give you an accurate reading (within the order of +-0.5%). You can even get add-ons for many digital multimeters which will do the same for you. I doubt that you ave access to a small portable CRO, but that's what I use.

If you can get a very accurate idea of your speed then you can do the maths and work out what rpm you should be doing at what speed. Apart from a table of gear ratios (including primary drive and final drive ratios) you'll need to measure the diameter of the wheel from where your speed is being read (front or rear) to within about 1mm. The more accurate the better with this measurement coz each step from here magnifies any measurement error. Do this with the bike loaded for most typical riding. Then convert that to a rolling circumference. It's basic arithmetic from there.

 

[Carlo Guzzi]

Speedos are deliberately calibrated to be optimistic - they read high! That's so that you can't blame the speedo manufacturer for your speeding tickets. In Oz the Australian Design Regulations (ADRs) require speedos to be within +10%-0% of actual speed. Your actual speed vs your indicated speed is dependent on factors like: tyre size, tread pattern, tyre wear, tyre inflation, load on the bike and prolly a few minor factors I can't think of right now. That's not to mention where in the +10%-0% your individual instrument lies. Note that that's a %age of actual speed. eg at an actual 100Km/h you speedo could well read (indicated) 110Km/h or even worse if you've played with tyre sizes or haven't pumped them up for a while.

A GPS (even an el cheapo automotive one) should give you something in the order of +-0.5% with good satellite coverage.

Tachos, on the other hand, can be and usually are calibrated quite accurately. Modern mass-production methods can easily give you +-2%. Trying to use a less accurate instrument to calibrate a more accurate instrument just isn't going to happen, except by accident! There are calibration instruments which will take an input from your ign coil or HT lead or CDI output and give you an accurate reading (within the order of +-0.5%). You can even get add-ons for many digital multimeters which will do the same for you. I doubt that you ave access to a small portable CRO, but that's what I use.

If you can get a very accurate idea of your speed then you can do the maths and work out what rpm you should be doing at what speed. Apart from a table of gear ratios (including primary drive and final drive ratios) you'll need to measure the diameter of the wheel from where your speed is being read (front or rear) to within about 1mm. The more accurate the better with this measurement coz each step from here magnifies any measurement error. Do this with the bike loaded for most typical riding. Then convert that to a rolling circumference. It's basic arithmetic from there.

Well, that was some extensive monograph - appreciate the effort I'm sure.
But look guys, this isn't complicated.
Will someone who owns a '98 EV (or same geared Cali) just look down at their tach and tell me what the rev reading is at 60 and/or 80mph?
NOT rocket science guys.
N.B. Todd, you have a cafe'd Cali, can you help?

 

[Dinsdale Piranha]

Well, that was some extensive monograph - appreciate the effort I'm sure.
But look guys, this isn't complicated.

Yeh, it is.

Will someone who owns a '98 EV (or same geared Cali) just look down at their tach and tell me what the rev reading is at 60 and/or 80mph?
NOT rocket science guys.
N.B. Todd, you have a cafe'd Cali, can you help?

What you want to do is fine, but I thought you wanted to know what rpm your engine is doing. Your idea is going to compound all of the other blokes inaccuracies with yours. There's little chance of getting any realistic rpm reading - except accidentally!

 

[Carlo Guzzi]

Yeh, it is.

What you want to do is fine, but I thought you wanted to know what rpm your engine is doing. Your idea is going to compound all of the other blokes inaccuracies with yours. There's little chance of getting any realistic rpm reading - except accidentally!

I am continually impressed by the erudite, technical and learned knowledge and opinions of forum members - and of course I am suitably humbled.
Thank you Dinsdale. Good on you mate!
Meantime, while I digest this newly found technical knowledge, will someone (please?) help me to compound their inaccuracies by giving a tach reading, in top gear, at 60 or 80 mph?
I mean, what is the problem here?

 

[Mackers]

My '02 EV (not hydro) is doing 3000rpm at 100km/hr (62mph). Don't know about 128kmh - that would be illegal!

 

[scottmastrocinque]

I have an MMB Tach that needs 'tuning' via the potentiometer....I mean, what is the problem here?

Hmm... I feel your frustration at what you believe should be a simple thing but as a previous owner of a 1998 California EV, I'd wager you couldn't get 2 out of 10 guys to give you the same reading with this instrument. In fact, the below photo I just grabbed off of the internet, is the only one I've ever seen with the tach actually at "zero". Mine and everybody else I ever saw with the same bike, our tachs looked like the second photo. Good Luck!

 

[jr1967]

I get the speed from a Speed app on my phone, plus the rpm's from my stroboscope taped to my tank bag for accurate readings.
Another way is to get the diameter of your rear tire plus gear box and final drive ratio's, so you can calculate rpm's versus speed in every gear. To have the most accurate reading you can measure the rear wheel diameter from the axle to the ground, this will compensate for the weight of the bike on the tire. But is hard to do without another person balancing the bike to keep it perfectly vertical.
The Bridgestone motorcycle tire web page has all the measurements, I compared them with other brand tires and they seem to be identical.
Hope this helps.

 

[jr1967]

From an on line manual of a California Stone. Not sure if it is the same as yours, but you get the idea....

1 2
Gearbox
5-speed, front engaging, constant mesh.
Incorporated Cush drive
Control pedal on left side of machine.
Gear ratios:
1st 1:2
(Z=14/28)
2nd 1:1.3889 (Z=18/25)
3rd 1:1.0476 (Z=21/22)
4th 1:0.8696 (Z=23/20)
5th 1:0.7500 (Z=28/21)
Final drive
Cardan shaft with gears
Ratio: 1:4,125 (Z=8/33)
Overall gear ratios (engine-wheel)
1st gear = 1:10,1912
2nd gear = 1: 7,0772
3rd gear = 1: 5,3382
4th gear = 1: 4,4309
5th gear = 1: 3,8217
Frame
High tensile stress modular duplex tubular cradle.
Suspension
Front: «MARZOCCHI Ø 45 mm" hydraulic telescopic
fork.
Rear: swinging fork with two adjustable SACHS-BOGE.
Wheels
Spoked with steel rims. Rim sizes:
– Front: 18"x2.50 - B-40 H2-T DOT or 18x2.50 B-40
H2-TC and DOT
– Rear: 17"x3.50 - B-40 H2-T DOT or 17x3.50 B-40
H2-TR and DOT
Tyres
– Front: 110/90 - 18 - 61H/61V/61VB
– Rear: 140/80 - 17 - 69H/69V/69VB
Brakes
Front: "BREMBO" semi-floating stainless steel disc with
fixed calliper and 4 differentiated pistons. Hand lever
control located on the right side of the handlebars.
– Ø disc 320 mm;
– Ø brake cylinder 30/34 mm;
– Ø master cylinder 13 mm.
Rear: fixed disc with floating calliper and 2 parallel
pistons. Pedal lever control located in the centre on the
right side of the vehicle;
– Ø disc 282 mm;
– Ø brake cylinder 30/32 mm;
– Ø master cylinder 16 mm

 

[Nordicnorm]

My '01 Jackal runs an Equus aftermarket tach (electronic, off one plug wire). At 3500 RPM I am indicating 120 km, at 4000 rpm 135 km/h.
The speedo is 10% optimistic against my GPS, so that would translate into 108 km/hr and 121.5 km/hr respectively. Because you are probably stuck with the same speedo error that has been around since Christ was a cowboy, (the Carcs are accurate), I would go with the first numbers. I've been staring at them for 10 years.
Hope you are not snowed in up there!