Forum

[ChrisD]

Hi guys. A while back I acquired a digital 2inch dia tachometer which I was assured would work with a Bullet (having one spark every 2 revolutions of the engine) providing I used a “single fire adaptor”.
So I bought the tachy and adaptor for my bullet.

Now I’ve fitted it, it is true that the tachy, without the adaptor, records only half the actual revs. But fitting the adaptor brings its own issues - because the adaptor has 3 wires, 2 to attach to both cylinders and one to attach to the tachy. I suspect the company that sold it didn’t tell me the whole truth (or at least didn’t understand their own answer).

BUT, now that I have this gear, can it be made to work?
I have a twin-plugged bullet but with a single coil, one of our hosts “dual” coils. If I used 2 separate coils, do you think that would make the single fire adaptor work correctly?
Alternatively could I fit both wires to my dual coil, and get the right response?
I’d appreciate any comments on this dilemma
Cheers, ChrisD

[KenKZN]

Hi ChrisD, perhaps the tacho is designed for two-stroke engines where each pulse (derived from ignition coil) represents one rev? Perhaps also the "single-fire adaptor" is for a two-stroke twin and outputs one pulse for every two (one from each cyl) to give correct revs/min on this tacho?

If the above is true then you'll need a different adaptor to create two pulses from every one (from low-voltage primary) from your coil, or a different tacho with 4-stroke single cyl option.

Also curious. Can you post pic and info on the units?

[Beezabryan]

Might work with Boyer or othr "lost sprk" set up ?

[Paul M H]

Even with a duel coil you will still only get one spark every two revolutions on the firing stroke with points. I think Beezabryan is correct you will need a lost spark set up as he suggests.

[ChrisD]

Thanks for the input guys.
KenKZN (in South Africa too?) The tachy was designed for a Harley-D. Early models seem to have a double-ended single coil hence the single-fire adaptor. Yes, I need to create 2 impulses for every fire. So I connected both leads from the ‘single-fire adaptor’ onto my dual coil negative terminal so that, essentially, there were 2 input signals from the coil. To no avail as the tachy still records half revs.

PaulMH, yes that’s what my dual coil does – one spark per 2 engine revs but I need 2 sparks hence my thought about two separate coils instead of my dual.

Beezabryan – yes, either an electronic system or another tachy. Both options way too expensive for me especially here in South Africa (Cape Town area). Also the twin plug Boyer system doesn’t have a wasted spark either.
Posting pictures – yes let me get back to Scaley’s notes and try later. I will copy onto photobucket (Chrisd200)
Cheers, ChrisD

[Beezabryan]

OK Chris I understand your predicament. How about a nice cheap option of somehow marking the face of the tcho with the correct rpm which weas something
Years back I did jus that with our Flash. It had a sidecar speedo but I was running it on solo gearing (before anyone gets it wrong the Flash speedo is driven from the gear box so the speedo does not know if you've changed the rear sprocket) With waterproof marker I marked the glasss to show true road speeds.

[Revband]

"The twin plug Boyer doesn't have a wasted spark". I think you will find that it does.

[Beezabryan]

Correct, one/two or more plugs make no difference Boyer will still fire twice

[Exile]

This really makes me wonder. We can put men on the moon, land a mini spacecraft full of all sorts of technical stuff on an asteroid millions of miles away in space, we have computers that can work almost anything out, artificial body organs, you name it, but NOBODY can make a simple plug and play tachometer for a Royal Enfield Bullet..??

Beggars belief....

[papasmurf]

I successfully fitted and electronic tacho my Electra X, BUT it was not simple to fit because it came with no instructions only three wired and finding the coil took time then no-one seemed to know which was the negative terminal on the coil when I did.