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Message started by emeraldcopnj on 09/24/14 at 08:32:34

Title: Speedometer
Post by emeraldcopnj on 09/24/14 at 08:32:34

I am looking to do a mini speedo on my bobber project. What ratio would I need? Thanks !

Title: Re: Speedometer
Post by mpescatori on 09/25/14 at 01:27:22

+1 I need to know myself.

Many aftermarket speedos are geared for anything from the ubiquitous harley Sportster to "younameit"
but I have obviously shoppet at "Murphy's", 2 speedos, 2 diferent ratios, still reads wrong...

:P

Title: Re: Speedometer
Post by justin_o_guy2 on 09/25/14 at 02:01:59

So,knowing those ratios,which way and how much,,bingo..

Title: Re: Speedometer
Post by PinkHelmet on 09/25/14 at 02:19:43

see if you can find anything from here:
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1345772898

Title: Re: Speedometer
Post by Demin on 09/25/14 at 05:18:22

There is a ratio for this.This is in the Dime City info:

60MPH @ 2240RPM...This is based on a Harley engine though,so don't be alarmed.

Here is one on Flea bay.

http://www.ebay.com/itm/New-Small-Drag-Specialties-Speedometer-2-1-2-Custom-Chopper-B363-/331228645749?pt=Motorcycles_Parts_Accessories&hash=item4d1ec40975&vxp=mtr

I run a 2:1 but I think it might be off.I also run a 150/90 rear tire. I have been thinking about getting this ratio and comparing.

Title: Re: Speedometer
Post by Arnold on 09/25/14 at 06:07:04

I have a 2:1 also, seems fairly accurate enough next to the side road speed radars.

Title: Re: Speedometer
Post by Kris01 on 09/25/14 at 18:28:17

2240:60 means the speedo cable must spin 2240 times for the gauge to read 60 mph.

Stock 140/80-15 = 74.829" circumference
846.731 rpms (of the tire) at 60 mph
2240/846.731 = 2.645

The stock speedo has a ratio of 2.645:1. I doubt the 2:1 ratio speedo is anywhere close to being accurate.

Title: Re: Speedometer
Post by mpescatori on 09/26/14 at 03:16:29

536A716B2829180 wrote:

Sorry, I don't agree.

2240/60 means an assumed 2240rpm (turns per minute) to read 60 mph.

By your own calculations, the Savage needs:
- 846.73 revolutions of the tire
- multiplied by 2.94 (belt drive ratio)
to read the same speed.

846.73 x 2.94 = 2489/60 (let's round this off to 2490/60 or even 2500/60)

So a 2240/60 speedo should read 2490/2240 = 1.11 11% faster than you are actually going.

The sppedo I fitted reads 10% slower than I am actually going, even though I now have a 2.88:1 chain drive and a 150/90x15 rear tire.

Had I a stock bike, it'd be reading 15% slower !!!

Explain THAT to a cop !!! :-X

Title: Re: Speedometer
Post by Dave on 09/26/14 at 04:42:07

Mechanical speedometers are so........yesterday! ::)

There are a whole new batch of electronic speedometers that not only offer the ability to get accurate speed information, you can get accurate odometer readings, trip odometer(s), engine and ambient air temperatures, time logs, altitude readings, turn signal and high beam indicators, shift and engine red line lights, etc. They are not too hard to install, and as time passes they are getting more affordable Entry level one are about $ 200 to install and some really fancy ones go for over $ 400. Some of the more recent ones even have conventional looking cases and swing needles for the tachometer. If accuracy is important and and money issue are not.....the GPS ones are really nice.

A few years ago all the electronic speedometers looked like lab equipment and did not look good on a bike - but the new ones look more like gauges we are used to seeing on motorcycles.

The fact is that s $ 60 mechanical speedometer is not going to read accurately on the wide range of bikes....maybe once in a while someone will get lucky and have the right gear ratio and tires size and it will read close enough.....and if you are building a simple bobber/rat bike and want a small speedo to check speed once in a while....they might read close enough. But if you want something useful and do a lot of riding.....by the time you buy a mechanical speedo, tach, and the cable to get them to work on the Savage - you will have spent about as much as an entry lever electronic speedo/tach will cost.

Title: Re: Speedometer
Post by Kris01 on 09/26/14 at 18:18:30

Mpescatori:
Check your calculations. That 846 tire revolutions per minute at 60 mph will have nothing to do with gearing. You can gear the bike anyway you want and you will still spin the tire the same exact RPM at 60 mph.

Remember, we are talking about tire rpms, not engine rpms. Obviously regearing will affect engine rpms.

Title: Re: Speedometer
Post by Dave on 09/26/14 at 18:31:21

4D746F753637060 wrote:

The reason that gearing affects our speedometer - is that the cable that drives the speedometer is driven from the transmission output shaft. Therefore when you change the gearing by changing the front or rear pulley/sprocket size...you change the number of revolutions of the rear wheel in comparison to the output shaft revolutions. That (and rear wheel spin) is one reason a lot of motorcycles use the front wheel to drive the speedometer.

Title: Re: Speedometer
Post by Kris01 on 09/26/14 at 18:49:37

Correct

Title: Re: Speedometer
Post by verslagen1 on 09/26/14 at 19:35:06

AND... neither one of you have accounted for the worm drive in the speedo gear.

Title: Re: Speedometer
Post by ToesNose on 09/27/14 at 13:59:55

I got the 60MPH @ 2240RPM one from Dime City along with a tach cable from the 73-77 GT550 and it corrected my speedo. ;)

Title: Re: Speedometer
Post by Dave on 09/28/14 at 18:22:57

This is only slightly off topic. Yesterday I saw a 1948 HRD...which later got the name Vincent. This was a Rapide, kind of the early model Black Shadow. (I may have some of that wrong....but that is the was I remember it being told to me). Anyhow....this is a speedometer and headlight set up that I believe looks really nice (no tach).

http://i59.tinypic.com/309iih1.jpg
http://i62.tinypic.com/2w2enf6.jpg
http://i60.tinypic.com/rser03.jpg

So.....I am tempted to look at electronic speedos with the tach integrated....to look a bit like this HRD.

Title: Re: Speedometer
Post by CHANMAN on 10/04/14 at 18:58:23

6C575A4D5C504B4D565E534C3F0 wrote:

So do these electronic speedometers work? If so where do you find them and what model

Title: Re: Speedometer
Post by Dave on 10/06/14 at 03:51:08

68636A65666A652B0 wrote:

So do these electronic speedometers work? If so where do you find them and what model

Yes they work. You have plenty to choose from - the only thing you should avoid is one that is made for a specific bike. Most of the aftermarket kits are universal - and they may offer some model specific parts. I know Acewell has some speedometer sending units that plug into the hole where the mechanical cable is driven. The installation most often requires mounting the speedometer, mounting a magnet and the sensor for the speedometer on the front wheel, and some simple wiring. The simple wiring may include a lot of wires if you get a speedo that show the indicator lights for the high beam, turn signals, and neutral light.

I have a Trail Tech Vapor on mine and it work well, and I have the dashboard that includes the indicator lights.....which unfortunately are not all that visible in the daylight. Acewell has a lot of models and some are flat like the Trail Tech Vapor....others are round and look more like a traditional motorcycle gauge.