Was your Tach/Hour meter not accurate ?

Chainlube

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https://www.amazon.com/Maintenance-...39d1e&pd_rd_wg=LiQjy&pd_rd_i=B07PMJH7QV&psc=1

I thought my first meter was defective, but now the replacement acts the same way. Did you experience this ? You can set these for 2 and 4 stroke engines with one or two cylinders depending on your application. Mine is 4 stroke one cylinder. It idles at 4200 rpm and I have seen it over 14,000 rpm at 2/3 throttle. I tried all three possible settings, closet being for a 4 stroke 4 cylinder or 2 stroke 2 cylinder. Without a real tach for reference I feel my idle is around 800 rpm and the tach shows 1150 rpm. I don't have enough hours on this yet to feel comfortable at W.O.T. checking the governor. I'm not sure what that rpm is on a HauSheng f142, do you ?

After riding for 20 minutes the hour meter shows 0.3 which seems to be right on. Maybe you can check the tach calibration by means of the hour meter ??

One thing that confuses me.......this device has a clock timer built in, obviously. To create a tach all you do is count the electrical pulses to the spark plug. The computer does the math. You need to tell it if it's 2 or 4 stroke so it can count correctly. Here's the question: why do the instructions ask "how many cylinders" ? It only triggers off one plug wire. It shouldn't matter if it was a V-8 because, hopefully, all the cylinders are operating at the same rpm. Anyway, I would like to hear about your experiences and how you resolved them. thank you
That one looks like the sealed one I used to have, I think it was $10 at the time, I use it to tune my saw. It's fairly accurate, the saw runs the best at 12,500 and pulls through the wood good. I would still have it, if I could have replaced the battery.

1150 sounds like a good idle for a motorized bike 4t, try turning you idle screw in and watch the tach and listen. You can return to your old idle setting at any time, just to check you device.
 

michael whiteman

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I just shared my issue with a good friend who is an electronics expert. He explained the clock circuit in this meter is totally independent of the rpm function. The only thing they share is: the clock triggers when it see the spark impulse and shuts off when the pulse stops. Great ! ...... so my hour meter is OK and the rpm display is still questionable. I'm going to find an automotive shop with an induction tach to check mine.
 

Karl Snarl

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Problem with using a cheap non shielded tach is whats going on. The em spike is causing it to go ape poop. A resistor plug or a resistor wire( either or dont use both) should help. Id imagine a resistor wire would be a better bet because the. Tach wire wraps around the spark plug cable. If these were better quality ignitions it wouldnt happen, but the tech is old that we use. So it doesnt account for electronics, there were none when these engine designs were made.
 

michael whiteman

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I stopped by a garage today and they said "sure bring your scooter by and I'll check it out". Maybe in a couple days. I don't think the lack of shiending has any thing to do with it Karl. You don't want the pick-up wire shielded because you are trying to pick up the inductive pulses. Contrary to the instruction sheet it makes NO difference as to how many turns I put around the plug wire. Maybe shielding in a multi cylinder engine might be a good idea so as not to pick up a pulse from an adjacent cylinder, but mine only has ONE cylinder. No...........I think it's just an inferior circuit design in the triggering portion of this meter. We'll see................
 

Sidewinder Jerry

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Make a video of what it's doing on all 3 settings. Like I said it has two 4 stroke settings. The 2 firings per revolutions is the first firing happens in the compression stroke. The second firing starts right at the beginning of the exhaust stoke to help burn exhaust gases. This is an EPA thing for motorcycles. You need the firing sequence for every other revolution.
 

michael whiteman

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I don't have a cell phone or a video camera Jerry. There's really nothing to see. The tach goes up and down but I'm not convinced that the numbers displayed are correct. I'll compare it with a professional tach at a local garage soon.
 

Karl Snarl

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I stopped by a garage today and they said "sure bring your scooter by and I'll check it out". Maybe in a couple days. I don't think the lack of shiending has any thing to do with it Karl. You don't want the pick-up wire shielded because you are trying to pick up the inductive pulses. Contrary to the instruction sheet it makes NO difference as to how many turns I put around the plug wire. Maybe shielding in a multi cylinder engine might be a good idea so as not to pick up a pulse from an adjacent cylinder, but mine only has ONE cylinder. No...........I think it's just an inferior circuit design in the triggering portion of this meter. We'll see................
I don't think you realize the size of the spike the ignition system puts out, it's creating a corona around the plugs ceramic. That means it's so powerful it ripped the electrons right off the air molecules. The resistor wire or plug will reduce the spike. You can read about it all on your own. Ever single car made today use's the tech, because they use electronics. The tach is cheap made with cheap parts. the em spike is producing interference in the circuits designed to measure the pulse. exactly why you are seeing wonky readings. Physics, ain't tht stuff great. Many , many , many other people, same problem. get rid of the cheap tach, or get a resistor wire. if it's not an em spike coming from an crazy leaky cdi system using copper wire for a spark plug wire, which happens to transfer great power, but also great interference...... why spark plug wires are carbon wires today, resistor wires.......
 

michael whiteman

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For 25+ years Karl I worked in the automotive field. A lot of my time was spent in R&D developing one of the first aftermarket add on FI systems. Our company had one of only four patents in the world on mass air sensors. Prior to that I can't tell you how many hi performance ignition systems I was involved in. It's a wonder my eyes haven't given out considering how many hundreds of hours I have spent staring at an oscilloscope. The funny car we ran out of the shop had two spark plugs per cylinder and fired at 44,000 volts so I know all about coronas, or better yet unscrewing a plug to find nothing inside except the threads. Back in the day carbon spark plug wires were first designed to keep ignition noise out of your radio. All of our testing was done on an engine dyno. Regarding (what they call) the CDI unit on a 4 stroke engine, I would really like to cut one open. From the outside they look just like an old school lawn mower coil, only with a terminal for a kill switch. Every CDI unit I have ever seen requires an outside 12v power source to activate the transistors in the circuit. I'll let you know if a professional inductive pick up tach gives me a more accurate reading after I take my bike to a local garage.


I want to amend what I said above about CDI systems. Just because I haven't seen them till now does not mean they don't exist. Kinda like flying saucers. Google actually shows internal electrical diagrams for CDI systems on small engines like ours. I can now see that it is possible to trigger a CDI with a very small voltage that is developed by the magnetic flywheel. Basically, it just takes a transistor with a lower threshold voltage. All of this circuitry must be encapsulated in that rectangular area where the plug wire originates. Which is pretty small for sure. One of the circuit diagrams was offered up by GruBee. Just be careful when looking through these that you do not get confused by the motorcycle diagrams that are shown.
 

Karl Snarl

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For 25+ years Karl I worked in the automotive field. A lot of my time was spent in R&D developing one of the first aftermarket add on FI systems. Our company had one of only four patents in the world on mass air sensors. Prior to that I can't tell you how many hi performance ignition systems I was involved in. It's a wonder my eyes haven't given out considering how many hundreds of hours I have spent staring at an oscilloscope. The funny car we ran out of the shop had two spark plugs per cylinder and fired at 44,000 volts so I know all about coronas, or better yet unscrewing a plug to find nothing inside except the threads. Back in the day carbon spark plug wires were first designed to keep ignition noise out of your radio. All of our testing was done on an engine dyno. Regarding (what they call) the CDI unit on a 4 stroke engine, I would really like to cut one open. From the outside they look just like an old school lawn mower coil, only with a terminal for a kill switch. Every CDI unit I have ever seen requires an outside 12v power source to activate the transistors in the circuit. I'll let you know if a professional inductive pick up tach gives me a more accurate reading after I take my bike to a local garage.


I want to amend what I said above about CDI systems. Just because I haven't seen them till now does not mean they don't exist. Kinda like flying saucers. Google actually shows internal electrical diagrams for CDI systems on small engines like ours. I can now see that it is possible to trigger a CDI with a very small voltage that is developed by the magnetic flywheel. Basically, it just takes a transistor with a lower threshold voltage. All of this circuitry must be encapsulated in that rectangular area where the plug wire originates. Which is pretty small for sure. One of the circuit diagrams was offered up by GruBee. Just be careful when looking through these that you do not get confused by the motorcycle diagrams that are shown.
Them cheap tachs cost like 30 cents to make. If that, no quality to em. I tried em as well. They suck, my cell phone to close can sometimes cause them to be a bit wonky. When i say shielded im not talking like military grade stuff. I do know most items are manufactured to accept any and all interference, says right on most things. An i suspect these cheap tachs are no different. Best tach i found was an aftermarket i snagged from a motorcycle grave yard. It got smashed when i wrecked my bike on the trails one day. Worked great though. Just cant remember who made it. Those cheapo golf cart ones dont help most of us out any at all. Most my bikes i don't bother logging hours or anything anymore. They last so long im not to worried. 😆. Plus once i figure the gear it gets out, i know about the speed im going by listening to the engine. I should have a tach on my nitro bike though, like to see how close i g0t with the homemade pipe.
 
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