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General Category >> Rubber Side Down! >> Help needed with installing a tachometer.
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Message started by darkstar on 09/16/08 at 18:28:01

Title: Help needed with installing a tachometer.
Post by darkstar on 09/16/08 at 18:28:01

Hi I've got a 07 S40, bought a tachometer for it that I believed to be single fire but turned out to be dual fire. The ebay seller I bought it from says it will work with the savage but I'm confused now as an other seller has an adapter that converts dual fire tachometers into single fire for the savage. So I'm in the dark now and before I do anything I would like to find this out. So my question is, is my S40 single fire or dual Fire...I would imagine it to be single fire...right?, as it only has one cylinder. Any info will be great. Thankz

I will be so >:( if I have to buy an adapter when the seller claims it to work with the Savage650/S40.

Title: Re: Help needed with installing a tachometer.
Post by verslagen1 on 09/16/08 at 20:34:17

The savage is a dual fire, it fires every revolution just cause.

Title: Re: Help needed with installing a tachometer.
Post by mpescatori on 09/17/08 at 02:04:27

73607776696462606B34050 wrote:

The savage is a dual fire, it fires every revolution just cause.

Exactly !

The Savage's ignition module is the same as many twins', it will fire every time the piston goes up, so once it ignites the air/fuel mixture and the engine goes bang! and the bike works... the then it fires again during exhaust phase to burn any unburnt residue and pull down those emissions...

So the bike is a "single cylinder, dual fire" bike, and your tach will do very well. ;)

Title: Re: Help needed with installing a tachometer.
Post by T Mack 1 on 09/17/08 at 03:19:01

Bike is dual fire BUT....... you need a single fire tach to meet the numbers that it is spec'd to.

Why...... has to do with terminology. True RPM, revolutions per minute and the term many companies use on engines which is engine cycles per minutes, which is the Compression strokes per minute.

I had a Honda CM250C which is a 2 cyl bike that fires simialr to the LS650, on the compression stroke and the exhuast stroke. It red-lines at 9500 rpm. Well, when I tried to a 12K Nova-MMB tach on it , it read double the bike's RPM. The tach had 1:1 on the back (single fire). Well, after I sold the Honda and when I got the LS650 running, I hooked up the tach tempoarily to the bike and it read fine.

Soooooooooo ... the Honda used the Engine cycles per minute to get their rpm number. Suzuki used the rev per minute to get their number.

So..... I would only but the tach first, try it and if it reads too high, get the adapter.

Title: Re: Help needed with installing a tachometer.
Post by mpescatori on 09/17/08 at 07:46:59

TMack, I may be wrong, but... the Honda only fired its spark on compression, right?
No spark on exhaust, compression only, right?

This means that, being a twin, it would fire every time the flywheel would rotate to a specific reference point.

The difference is the Honda would share sparks between its two cylinders, while the Suzuki only has one cylinder.

RPM Revolutions per Minute is referred to the engine crank => the flywheel, not the camshaft.

Title: Re: Help needed with installing a tachometer.
Post by T Mack 1 on 09/17/08 at 11:18:43

607D687E6E6C79627F640D0 wrote:

No, the Twinstar 250 engine has two parallel cylinders and the pistons both go up at the same time. One in compression , one exhausting. They have one Ign coil wiith two HV wires coming out, that fires both at same time. So, they fire like the LS650 , on the exhaust & compression strokes. The flywheel pick-up is also like ours, so it fires every revolution. It is only different in that for every up-stroke there will be a power stroke result, first one cylinder, then on the next stroke the other, then the other, then the other.....

I'm trying to get people to understand that there are varying terminology that the manufacturers seem to use as they see fit.

Title: Re: Help needed with installing a tachometer.
Post by T Mack 1 on 09/17/08 at 13:48:35

Started a Thread in the tech ref section to list tachs that are known to work.

Any one readuing this that has a tach that works please reply to the Tech Ref thread......

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1221683647

Title: Re: Help needed with installing a tachometer.
Post by darkstar on 09/17/08 at 18:59:23

Thanks guys for the info, I will see what happens tomorrow when I go to hook her up, I guess if it works it works and if don't I'm mad!