Author Topic: RPM vs MPH chart for Super Meteor 650  (Read 235 times)

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iradel

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on: July 07, 2024, 09:25:40 pm
(Since the Super Meteor 650 doesn’t have a tach,) I’m looking for a RPM vs MPH chart along the lines of this one for the Classic 350: https://forum.classicmotorworks.com/index.php?topic=36062.msg464506#msg464506

Has anyone come across one?


AzCal Retred

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Reply #1 on: July 08, 2024, 12:04:23 am
Calculate with gear ratios/final drive ratio/wheel diameter?
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Hog Head

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Reply #2 on: July 08, 2024, 03:38:34 pm
I did that calculation for both stock and the optional "38T" gearing as part of the belt drive design - data here:

https://www.royalenfieldbeltdrive.com/product-page/super-meteor-shotgun-650-belt-drive-kits

Ducati Supersport S
Harley XR1200
Triumph T-120 Bonnie (Hinkley)
RE 650 Interceptor
Harley XL1200R


axman88

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Reply #3 on: July 08, 2024, 03:41:44 pm
(Since the Super Meteor 650 doesn’t have a tach,) I’m looking for a RPM vs MPH chart along the lines of this one for the Classic 350:

Has anyone come across one?
It's not as simple as a single chart, because one would generally choose some ratio other than top gear at city speeds, while top is most appropriate to economy cruising.

If you can provide the ratios, I can add a column to my spreadsheet that calculates such things for purposes of comparing the known, ( bike's I have owned), to those I might possibly like to own.  My spreadsheet offers an RPMs / MPH number for a few gears, along with Rpms at a couple of speeds.

The calculation requires:
  Primary drive ratio
  Transmission ratios
  Final drive ratio
  Drive tire circumference

The site below offers extensive charting of this relationship for various machines, and also apparently incorporates a horsepower calculator which accounts for air drag, as they display graphs which show top speed limited by power, as well as by rev. limiter value.  Unfortunately, no Royal Enfields.  Here's a Honda Shadow for reference:  https://www.motorbikecatalog.com/performance/1999/64970/honda_shadow_750_vt750c.html

The site generates a lot of data, with mathematical models, but unfortunately, I've found some machines on it, which have incorrect ratio numbers, which means garbage out.


AzCal Retred

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Reply #4 on: July 08, 2024, 05:09:31 pm
School zones and highways often have speed sensing signs. Find one and see what the RPM is for that speed & gear. Speed is proportional to RPM, do the math for 4th & 5th. If you know RPM for 30 & 60 you can stay out of trouble.  (Hint: just because a cop passes you at 75 on a posted 65 MPH road doesn't mean it's a "Snow Day" and you get to follow him 100 feet back off his bumper...) ;D
A trifecta of Pre-Unit Bullets: a Red Deluxe 500, a Green Standard 500, and a Black ES 350.


AzCal Retred

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Reply #5 on: July 09, 2024, 02:34:57 pm
RPM metering at a glance! I love the translated product description - "Intimate and reliable". I'm wondering what they think WE do with tachos...? :o

HOKARUA
1pc Gasoline Engine Digital Tachometer Meter LCD Digital Display Timer Gauge
Free 30-day returns
$4.88

https://www.walmart.com/ip/1pc-Gasoline-Engine-Digital-Tachometer-Meter-LCD-Digital-Display-Timer-Gauge/5254903485

Description
This is a gasoline engine timer, digital display design, LCD screen display, clear and intuitive, convenient for you to watch. It is made with excellent craftsmanship, professional and efficient, and can be widely used in motorcycles, racing vehicles, lawn mowers, etc. This gasoline engine timer is very practical and will be your good choice.

Features
-Color: Black.
-Material: ABS.
-Size: About 7.35X4.67X2.00cm/2.89X1.84X0.79inch
-The timing range is: 0.1-9999.9 hours.
-Support speeds range: 15300 RPM.
-Voltage: 3 (V).
-Power: 0.002-0.03 (W).
-Low voltage design, built-in battery power supply, safe and reliable, and long service life.
-Professional and efficient, with a wide range of applications, it can be used in motorcycles, lawn mowers, etc.
-The design is reasonable, with LCD display screen to facilitate you to read data better and more convenient.
-Intimate and reliable, the maintenance time reminder function can be set, and the LCD screen flashes to remind when the time is up.
-The structure is simple, the application is convenient, you can easily install and use.
Low voltage design, built-in battery power supply, safe and reliable, and long service life
|Professional and efficient, with a wide range of applications, it can be used in motorcycles, lawn mowers, etc
|The design is reasonable, with LCD display screen to facilitate you to read data better and more convenient
|Intimate and reliable, the maintenance time reminder function can be set, and the LCD screen flashes to remind when the time is up
|The structure is simple, the application is convenient, you can easily install and use
info:

A trifecta of Pre-Unit Bullets: a Red Deluxe 500, a Green Standard 500, and a Black ES 350.


axman88

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Reply #6 on: July 09, 2024, 04:21:13 pm
HOKARUA
1pc Gasoline Engine Digital Tachometer Meter LCD Digital Display Timer Gauge
$4.88

I bought a one of these, then another one, when I misplaced the first.  Mine came from Ebay, for about $7.50 ea, shipped.  With this Chinese stuff, it's not impossible that the external appearance is identical, but the circuitry is quite different, from different manufacturers.   The documentation that came with mine was pretty sketchy, and it was difficult to decide from the description, which setting was appropriate to the engine I was trying to work on.  It has settings for wasted spark and multi-cylinders, up to a point.  But, it was kind of obvious, to my somewhat experienced ear, which setting was correct, 450, 900 and 1800 rpms sound pretty different. 

Pro tip:  multiple wraps of the "sense wire" helps.  I use 5 turns, tightly clamped to the spark plug wire.

Although it's been fine and useful for setting idle and diagnostics at low rpm, the circuit seems to have a hard time with accuracy at higher rpms.  Above about 3000rpms, my tacho/hour meter got pretty stupid, slow to react, and values jumped around by a few hundred.  I would anticipate disappointment if I planned on mounting this permanently to my high revving sport bike.  The gadget is designed more for utility engines, so this shouldn't be breaking news.

This weakness shouldn't be a deal killer in this application, since one could putt putt around town in various ratios, and get their measurements.  Personally, I wouldn't trust those speed display road signs, those have a definite agenda, and no requirement to be calibrated.  They may well perform their role better by lying, just as vehicle speedometers do.  I've found different ones will report values both above and below my speedo reading by a good 10%, less accurate than the on-board speedometer.

If I wanted accuracy, I'd use a GPS gadget.  There are free apps for one's phone that do this, Google "Speedometer app". 

And, one is still going to have to measure their rear wheel circumference, and do some math, to get ratios out of speed and rpm data.  I wonder how much one should derate unloaded circumference to get effective circumference at different air pressure values?

There is another way that is arguably safer, more accurate, and less equipment intensive, besides looking up ratio values online, (RE is good about publishing tech. data, unlike SOME manufacturers) and using math.  One can prop. up their rear wheel, take out spark plugs, chalk mark the rear tire, and spin it while engaged to the engine in various ratios, while counting rear wheel revolutions and the number of times the piston does its up and down thing.   I use a nice piece of HDPE plastic rod for poking into spark plug holes.  It's slick, it's soft, it won't splinter, and I'd have to work pretty hard to break something, but I'm still very careful when doing this sort of thing.