Good tach, bad _________ ? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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Where does this wire go?
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post #1 of 26 (permalink) Old 02-20-2016, 11:47 PM Thread Starter
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Good tach, bad _________ ?

My tach 'works' as well as the alleged "test" in the service manual goes. In fact, my tach acts like a crazy spooked cat on LSD chasing imaginary flies. When the bike is off, the tach is at zero. When the bike idles, the tach sort of tries to make up its mind between 1k and 2k rpm about 5 times per second... ( just keeps bouncing between the two ). On the road, occasionally, somewhere past 35 mph, it decides to suddenly jump up to 7k then bobbles between 7k and red line ( same sort of bobbling it does at idle ). My tach couldn't care less how fast the engine is turning, but, i am convinced it at least "works".

Which leads me to my questions... The service manual states right up front that the tach "test" presumes the entire electrical system is working. Okay... so... the question is... what does the "other end" of the tach wiring hook up to? Is it a sensor someplace? Is it the ignitor? The R/R? both? Is it hooked to the wire that drags the crushed beer can behind the exhaust pipes with the antennae on top? That would certainly explain the way it acts.

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post #2 of 26 (permalink) Old 02-21-2016, 12:46 AM
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the take gets a signal from the black wire on the front coil.. the connector could be loose causing your symptoms
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post #3 of 26 (permalink) Old 02-21-2016, 02:43 AM Thread Starter
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Quote:
Originally Posted by slimvulcanrider View Post
the take gets a signal from the black wire on the front coil.. the connector could be loose causing your symptoms
Thank you! I've taken the entire assembly apart. Cleaned it, etc. I decided not to replace the bee inside the tach, or the spider inside the speedo. Other than that though, i went as far as pulling the bulbs in the entire assembly and washing the plastic parts in the sink. Cleaned all of the connectors in the harness, etc.

So, the black wire on the front coil will be tomorrow morning's task at first light. Thank you again!

P.S. When i am comfortable enough with pulling off the fuel tank, i intend on building a brand new harness from scratch; actually two, one for each side instead of the huge single trunk. I'll be using the modern kind of automotive conduit instead of electricians tape as well.

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post #4 of 26 (permalink) Old 02-21-2016, 05:52 PM Thread Starter
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Originally Posted by slimvulcanrider View Post
the take gets a signal from the black wire on the front coil.. the connector could be loose causing your symptoms
Coil has a red wire and a black wire, but the black wire goes back up into the harness. So i guess i need to cut the harness up and trace it back up the neck.

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post #5 of 26 (permalink) Old 02-21-2016, 07:26 PM
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yup just looked at my diagram.. deifnantly the black wire to the tac from the coil.. both wires come from the cdi.. but the red goes to the other coil as well.

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P.S. When i am comfortable enough with pulling off the fuel tank, i intend on building a brand new harness from scratch; actually two, one for each side instead of the huge single trunk. I'll be using the modern kind of automotive conduit instead of electricians tape as well.
been there done that. scrapped about 50 miles of spaghetti lost 90% of the redundant electrical BS. is it worth the time and effort.. depends on whats going on in the rats nest.
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post #6 of 26 (permalink) Old 02-21-2016, 07:59 PM Thread Starter
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Quote:
Originally Posted by slimvulcanrider View Post

been there done that. scrapped about 50 miles of spaghetti lost 90% of the redundant electrical BS. is it worth the time and effort.. depends on whats going on in the rats nest.
I am also thinking about pulling out all of the bulbs and replacing them with LED's with a resistor on the back. Need to do some homework on that first though to see if it's worth the effort in regards to saving current drain on the battery. LED technology has improved 1000 fold over the past 30 years. So if i can find a good LED that has at least the same candle power as the stock bulbs, uses less current to drive one, . . .
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post #7 of 26 (permalink) Old 02-21-2016, 08:05 PM
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Quote:
Originally Posted by RoadHopper View Post
I am also thinking about pulling out all of the bulbs and replacing them with LED's with a resistor on the back. Need to do some homework on that first though to see if it's worth the effort in regards to saving current drain on the battery. LED technology has improved 1000 fold over the past 30 years. So if i can find a good LED that has at least the same candle power as the stock bulbs, uses less current to drive one, . . .
LEDs are worth the effort, but if you use a resistor it cancels out the power savings. Just swap the flasher to the one compatible with LED. I have the number somewhere, been posted here too, have one on my bike.

The cheapest LEDs aren't so bright, best to pay a bit more. Have a couple of $3 bulbs in my tail light, now I need the good ones. The el cheapo license plate bulb is plenty bright though.

Before I would yank the harness, I'd test both ends of the wire in question.

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__________________________________________________ ____________
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post #8 of 26 (permalink) Old 02-21-2016, 08:11 PM
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Quote:
Originally Posted by RoadHopper View Post
I am also thinking about pulling out all of the bulbs and replacing them with LED's with a resistor on the back. Need to do some homework on that first though to see if it's worth the effort in regards to saving current drain on the battery. LED technology has improved 1000 fold over the past 30 years. So if i can find a good LED that has at least the same candle power as the stock bulbs, uses less current to drive one, . . .
again its been done before.. although i didn't use resistors. i was lightening the load to add it back elsewhere.
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post #9 of 26 (permalink) Old 02-21-2016, 08:13 PM
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Quote:
Originally Posted by Spockster View Post
LEDs are worth the effort, but if you use a resistor it cancels out the power savings. Just swap the flasher to the one compatible with LED. I have the number somewhere, been posted here too, have one on my bike.

The cheapest LEDs aren't so bright, best to pay a bit more. Have a couple of $3 bulbs in my tail light, now I need the good ones. The el cheapo license plate bulb is plenty bright though.

Before I would yank the harness, I'd test both ends of the wire in question.
all 4 ends of wire in question... both sides of the 9 pin connector under the neck cover, the plug on the coil, and then the plug on the tac.
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post #10 of 26 (permalink) Old 02-21-2016, 08:34 PM Thread Starter
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Originally Posted by slimvulcanrider View Post
yup just looked at my diagram.. deifnantly the black wire to the tac from the coil.. both wires come from the cdi.. but the red goes to the other coil as well.
.
Okay, so, i disconnected the 6P and took the black wire off the coil. The connection is fine ( wire is intact in the harness ). That leaves the black node to ground which is the "arrow" end in the diagram. That gave me a reading of 40 ohms to ground.

The bike fires just fine. the 6p connector is clean, but i'll need to rig up a mount of some kind to test the tach circuit any further since i only have two hands and work in a parking lot.

What kind of reading should that 40 ohms be? It's the primary side of the coil, correct?
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