Calibrating an inductive tachometer

[Tanshanomi]

I just installed a Runleader RL-HM032C tach on my bike. It's a fairly generic battery-operated inductive digital tach of the type you find all over Amazon and Ebay.

The revs seem to be reading unrealistically high. I'd like to know if anybody has any tips for getting this to read correctly.

I set the firing pattern to 1 spark per crank rev, and wrapped the signal wire around the plug wire 4 times, as instructed. However, in the operating instructions, it has this:



As I said, I have the wire wrapped around the plug lead 4 times, as instructed. But I have to wonder — how am I supposed to determine what's an accurate reading? If I had some way to know for sure whether the RPMs were too high or low, I wouldn't need the damn tach unit!

I am sure I'm no the only person to play with one of these, so any help would be appreciated.

 

[Minimichael]

I messed with the spark per stroke setting on mine and felt the logic was misleading but just found one that was accurate. And by that I mean it sounds more or less true.

I also wrapped it around more than 4 times. Five or six...

 

[BrownStainRacing]

I just installed a Runleader RL-HM032C tach on my bike. It's a fairly generic battery-operated inductive digital tach of the type you find all over Amazon and Ebay.

The revs seem to be reading unrealistically high. I'd like to know if anybody has any tips for getting this to read correctly.

I set the firing pattern to 1 spark per crank rev, and wrapped the signal wire around the plug wire 4 times, as instructed. However, in the operating instructions, it has this:

View attachment 305891

As I said, I have the wire wrapped around the plug lead 4 times, as instructed. But I have to wonder — how am I supposed to determine what's an accurate reading? If I had some way to know for sure whether the RPMs were too high or low, I wouldn't need the damn tach unit!

I am sure I'm no the only person to play with one of these, so any help would be appreciated.

I use the runleader tach/temp, sold and installed a few.

Try 6-8 wrapped around the plug wire, and keep the coils tight against each other.

The stock OHV clones will idle 1400-1800.

 

[Minimichael]

Here's the one I'm using..
Small Engine Tachometer Hour Meter: Timorn Digital Inductive Waterproof Tiny Tach Meter & RPM Meter & HR Meter for Dirt Bike | Chainsaw | Lawn Mower | Generator Motorcycle Boat Marine Outboard https://a.co/d/fj97Cqd

 

[Thepaetsguy]

I have the same run leader tacs about 1200rpm at idle and wound out over 40mph says about 3950rpm’s I have a t/q though. Rain or deep snow they seem pretty durable. I wrapped mine around the plug wire directly as pictured.

 

[Studeman68]

I just installed a Runleader RL-HM032C tach on my bike. It's a fairly generic battery-operated inductive digital tach of the type you find all over Amazon and Ebay.

The revs seem to be reading unrealistically high. I'd like to know if anybody has any tips for getting this to read correctly.

I set the firing pattern to 1 spark per crank rev, and wrapped the signal wire around the plug wire 4 times, as instructed. However, in the operating instructions, it has this:

View attachment 305891

As I said, I have the wire wrapped around the plug lead 4 times, as instructed. But I have to wonder — how am I supposed to determine what's an accurate reading? If I had some way to know for sure whether the RPMs were too high or low, I wouldn't need the damn tach unit!

I am sure I'm no the only person to play with one of these, so any help would be appreciated.

1 spark per rev is a 2 stroke. I would change the setting to reflect a 4 stroke and see what it reads.

 

[sparkwizard]

Magneto ignition sparks every time the magnet passes the coil, doesn't it? With a distributor, you would have one spark per cylinder every 2 revolutions, but a single cylinder magneto fired engine fires at TDC, compression and exhaust, One spark per revolution should be correct.

 

[Tanshanomi]

1 spark per rev is a 2 stroke. I would change the setting to reflect a 4 stroke and see what it reads.

The simple ignitions on these motors rotate with the crank, not off the camshaft. They fire once per revolution, aka “wasted spark” ignition.

 

[Minimichael]

1800rpm sounds different enough from 900rpm, or 3600. I set mine up by ear.

 

[Thepaetsguy]

1800rpm sounds different enough from 900rpm, or 3600. I set mine up by ear.

I do like the hour meter part of it more then the tac.

 

[Tanshanomi]

I bought a $20 optical tach off Amazon. It measures using laser reflections, so it can measure the speed of any rotating shaft. I wrapped black electrical tape around the outside of the clutch and a bit of the reflective tape that comes with the unit. I started up the bike, and after a bit of trial-and-error to get the laser beam positioned properly, got a steady reading at idle. And, waddayaknow, the Runleader tach was spot-on, actually within 15 RPMs of the handheld unit.



Just for the record, here is now I have the wire attached to the spark lead:



So, all of this tells me a couple of different things:

• I had my idle higher than I thought.
• My drive belt starts to engage higher than the 2000-2100 RPM speed I expected.
• My engine is blowing past the 4000 RPM safe limit of the flywheel before the CVT maxes out the gearing, which I was hoping would not be the case.

The biggest conclusion for me is that I truly don't know the first thing about CVT tuning.

 

[Thepaetsguy]

I bought a $20 optical tach off Amazon. It measures using laser reflections, so it can measure the speed of any rotating shaft. I wrapped black electrical tape around the outside of the clutch and a bit of the reflective tape that comes with the unit. I started up the bike, and after a bit of trial-and-error to get the laser beam positioned properly, got a steady reading at idle. And, waddayaknow, the Runleader tach was spot-in, actually within 15 RPMs of the handheld unit.

View attachment 306007

Just for the record, here is now I have the wire attached to the spark lead:

View attachment 306008

So, all of this tells me a couple of different things:

• I had my idle higher than I thought.
• My drive belt starts to engage higher than the 2000-2100 RPM speed I expected.
• My engine is blowing past the 4000 RPM safe limit of the flywheel before the CVT maxes out the gearing, which I was hoping would not be the case.

The biggest conclusion for me is that I truly don't know the first thing about CVT tuning.

my genuine comet belt after running for well over 75 miles and 14 hours looks basically brand new. I pack my t/q with grease and pull it down every four hours for extensive cleaning and re-grease. Your just going to have to put someone else on this bike and follow behind it on something else. watch the t/q at cruising I bet the belt alignment at cruising is way off like both of mine were when I first built these karts. The driver just pushes the belt a bit further towards the engine then you intend. the driven can’t open enough to bring the belt over towards the engine to correct that alignment. So you might need another spacer behind the driver. I found that alignment when the karts is not in use is hard on belts. getting it close not in use THEN setting the alignment based off what the belt does in use has been a massive success twice for me. You can’t look down and eyeball it while riding either.. you have to follow behind it.

 

[Tanshanomi]

my genuine comet belt after running for well over 75 miles and 14 hours looks basically brand new. I pack my t/q with grease and pull it down every four hours for extensive cleaning and re-grease. Your just going to have to put someone else on this bike and follow behind it on something else. watch the t/q at cruising I bet the belt alignment at cruising is way off like both of mine were when I first built these karts. The driver just pushes the belt a bit further towards the engine then you intend. the driven can’t open enough to bring the belt over towards the engine to correct that alignment. So you might need another spacer behind the driver. I found that alignment when the karts is not in use is hard on belts. getting it close not in use THEN setting the alignment based off what the belt does in use has been a massive success twice for me. You can’t look down and eyeball it while riding either.. you have to follow behind it.
View attachment 306009 View attachment 306010

Wow, I didn't even consider alignment as an issue. Viewing it from behind would be difficult on my bike. The frame and swingarm block any view of the belt to the rear. Perhaps I can mount my GoPro somewhere on the bike that will record a proper view of it in action.