Tach on a single cylinder

[Miles]

Is it possible to attach a car tachometer to a single cylinder engine? or just some types of tach?

 

[Doc Sprocket]

Yes, but it has to be electronically modified to read accurately. Check this thread- http://diygokarts.com/vb/showthread.php?t=7785

Option #2- Google "Tiny Tach"

Option #3 is a pricey one, being a racing unit, can't think of the name right now- somebody will chime in.

 

[anderkart]

Option #3 is a pricey one, being a racing unit, can't think of the name right now- somebody will chime in.

Yeah those race kart tachs are like in the $200-$400 range but they include a temp gauge plus a bunch of other features you probably dont need.
You'll find some here: http://www.cometkartsales.com/store/gauges/gauges.htm

Is it possible to attach a car tachometer to a single cylinder engine? or just some types of tach?

You'd need a 12 volt power source, but an automotive tach should function connected to your kill switch wire.

Your GX340 fires every revolution, on both the power and exhaust strokes.

So a 4 cylinder tach would most likely only read 1/2 of your actual rpm.
A tach calibrated for a 6 cylinder engine would only read out 3/8.
And a V8 tach only 1/4 of your actual rpm.

An electric-tach off a single-cylinder/4-cycle motorcycle should read accurately. Or even a twin/4 stroke if they happened to of fired both cylinders simultaneously with a single coil.

I'd think some 2 cylinder/2-cycle tachs would read accurately too.

But the Tiny-tach is the only reasonably priced option I know you can just slap on and it'll work right: http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GZAZ_enUS369US369&q=tiny+tach

 

[daniel7250]

good ol' ebay http://cgi.ebay.com/Tachometer-Hour...732?pt=LH_DefaultDomain_0&hash=item33657f704c

 

[Miles]

So, I've got this tach, its off a good o'l 6 cylinder john deere, it honestly doesn't matter to me that it will only read 3/8 of the actual speed when hooked up, I'm just wondering if any one can tell what wires go where just to make the thing ''work''. I've got a brown wire, a positive (top) a negative/ground (left) and the ''tach input'' (bottom)
http://www.flickr.com/photos/60812573@N07/5542412200/

 

[anderkart]

Tach INP. goes to engines kill switch wire. (or possibly negative post of external type coil if equipped )

+ goes to positive side of 12-volt battery through any type of on/off switch.

- goes to battery ground.

Your brown wire appears to be attached to a light bulb socket for night time illumination. (that socket should easily pry out to change the bulb) So you could connect it to your light switch if you have one, or just hook it up to your on/off switch if you ride at night. Or you dont have to hook it up at all.

 

[Miles]

Your my hero. thank you soo much, it worked like a charm

 

[anderkart]

Yer welcome.

 

[devino246]

So, I've got this tach, its off a good o'l 6 cylinder john deere, it honestly doesn't matter to me that it will only read 3/8 of the actual speed when hooked up, I'm just wondering if any one can tell what wires go where just to make the thing ''work''. I've got a brown wire, a positive (top) a negative/ground (left) and the ''tach input'' (bottom)
http://www.flickr.com/photos/60812573@N07/5542412200/

Theres an instructables about how to make tacs for multi-cylinder engines read correctly on small engines.

 

[Screendoor]

I think I might order one now!

 

[Miles]

Here's a video of it in action, my quad project isn't running yet, so I just put it on a 5hp briggs to test http://www.youtube.com/watch?v=B4uZBzKBr4E

 

[anderkart]

Cool, good job

 

[devino246]

I suppose if you wanted to, you could pop the glass off that thing and make a new background with the correct scale.

 

[anderkart]

I suppose if you wanted to, you could pop the glass off that thing and make a new background with the correct scale.

Wow that's an freakin awesome idea devino...

I'm impressed and kinda ashamed I didn't think of it.

Most any automotive tach could be fairly easily disassembled and have this done. It would probably still require side by side comparison with an accurate tach to do a 100% accurate re-labeling, but realistically the only truly meaningful tach info most of us here would ever need is just where redline and normal Idle speed is.

Heck to make this simple, someone could just take a high speed ride and use a sharpie to mark the outside of the tachs lens where the max RPM they feel comfortable revving to was, and then also mark their normal Idle speed.

You wouldnt necessarily need to know the exact rpm unless you had a highly modified engine, and those guys should probably just buy a tach that's correctly calibrated for their engine type anyway.

But once again, great Idea man

 

[devino246]

Ive been meaning to get a tach & modify it like in that instructables but Ive been saving for a truck (which Im finally buying ) and im too frugal to spend $30.

 

[anderkart]

I'm not so sure those instructable modded tacks are all that accurate, I'd wanna see a side by side comparison against a racekart tach to totally believe it.

Back when I used to wrench on cars at an auto electrical specialty shop I ran across lots of fuel, temp and oil pressure gauges (or sometimes the sending units ) that still functioned, but they're accuracy had simply drifted. Like the car ran out of gas with the gauge still reading 1/4.

When the new part wasn't available (or the customer couldn't afford it) I used to paint small marks on the front of the gauges faceplate or the lens signifying where the low, mid-point and high readings were accurate.

That's why I was so surprised I didn't even think to do this with these DIY go kart tachs. My brain must be fading and yours still sharp!

 

[devino246]

I'm not so sure those instructable modded tacks are all that accurate, I'd wanna see a side by side comparison against a racekart tach to totally believe it.

Back when I used to wrench on cars at an auto electrical specialty shop I ran across lots of fuel, temp and oil pressure gauges (or sometimes the sending units ) that still functioned, but they're accuracy had simply drifted. Like the car ran out of gas with the gauge still reading 1/4.

When the new part wasn't available (or the customer couldn't afford it) I used to paint small marks on the front of the gauges faceplate or the lens signifying where the low, mid-point and high readings were accurate.

That's why I was so surprised I didn't even think to do this with these DIY go kart tachs. My brain must be fading and yours still sharp!

I dont really see how that mod would alter the accuracy, unless you use the wrong size capacitor or resistor or whatever the thing that you had to switch.

The tach that miles looks like the perfect candidate for a faceplate repainting though, because of the low rpm registry. Maybe Ill eventually try that...

 

[Doc Sprocket]

I'm really going to have to do something like this. The tiny tach may work well, but the digits are small, and I largely prefer analog sweep gauges. I'm not sure I've got the TPI for the electronic mods, so maybe the face-job is a functional idea.

Out of curiosity, how many cylinders was that tach supposed to read, or if it was a 4-6-8, what was it set for?

 

[element10554]

http://www.shipstoday.net/products/Small-Engine-Tachometer-Hours-Meter.html
Figured I would share this with you guys. I just purchased this a few days ago although they are not true to their word about the shipping today part (you only get a tracking number which takes 2 days to actually activate) I will post and let you know how it works on my engine. I only got this as to see the rpm's my engines are actually running at. So it will not be a permanent application to any one of my engines. Simply a tester

 

[Miles]

hey toystory, that tach I used was pulled out of a john deere 710B turbo, I believe it was a 6 cylinder engine