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Discussion Starter · #1 ·
I am trying to help a friend (which we all know can be a mistake). It's a '07 Brute Force 750 and has no spark. The ignition switch, and kill switch are both working properly. The primary voltage to the ignition coils is only 8 volts while cranking (using a peak reading adapter). the spec is 130 volts or more.
I followed the manual to test the Vehicle Down Sensor. On the 12v circuit, I have 11.8 volts to the Brown - Black/yellow wires (pass). On the 5v circuit, I have 10.5 volts between the yellow/green - black/yellow wires (fail, should be around 5 volts) Both tests were done with the sensor disconnected and testing voltage from the harness.
On the sensor output circuit, I have .732 volts to the blk/y - y/gn with the sensor pointed UP (pass, spec is 0.4 - 1.4 volts). and 7.4 and 8.4 volts with the sensor tilted (fail, spec is 3.7 - 4.4v) This test was obviously done with the sensor hooked up.
The 10.5 Volts on the 5 volt circuit raises a red flag for me. According to the service manual, the yellow/green wire goes to the Vehicle down sensor from the Igniter. I don't want him to disk out the $$$ for a new Igniter unless I'm sure this is the problem. Is it common for Igniters to fail on these machines?
 

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I don't know if it's common for "this bike' but they do fail. I have purchased used ones off of EBAY, just to have back up ones, the one for my bike is ridiculously expensive new. These run from $170, to $200 bucks used on EBAY. Dynatek sells a new one for $229. If you've checked everything, then it becomes an "Occam's Razor" type thing, the only thing left is most probably what it is (that's an intepretation)

Occam's Razor:
Occam's Razor, put simply, states: “the simplest solution is almost always the best.” It's a problem-solving principle arguing that simplicity is better than complexity. Named after 14th-century logician and theologian William of Ockham, this theory has been helping many great thinkers for centuries...........stolen from Google :)
 

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Wouldn't a light be flashing? On the other hand, if it fails, Maybe the light doesn't flash? Bypassing it should let the bike start. That seems like one of the 1st things you try, as long as the Ignitor doesn't have to "see" the circuit there to start. None of my motorcycles have fuel injection, or a "Vehicle down sensor". I would definitely jump this connection, provided that jumping it just takes it out of the circuit, "as if it didn't exist". Not being a Kawsaki owner till now, I'd only heard of this kind of sensor on my Ford Taurus. It has one if the car is hit in the back. You reach in the trunk and reset the switch manually. Very interesting! :)
 

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Discussion Starter · #5 ·
Wouldn't a light be flashing? On the other hand, if it fails, Maybe the light doesn't flash? Bypassing it should let the bike start. That seems like one of the 1st things you try, as long as the Ignitor doesn't have to "see" the circuit there to start. None of my motorcycles have fuel injection, or a "Vehicle down sensor". I would definitely jump this connection, provided that jumping it just takes it out of the circuit, "as if it didn't exist". Not being a Kawsaki owner till now, I'd only heard of this kind of sensor on my Ford Taurus. It has one if the car is hit in the back. You reach in the trunk and reset the switch manually. Very interesting! :)
I'm not sure that this can be bypassed. If it can, I'm not sure which direction to bypass it. The strange thing is, The 5V circuit is way high but the output voltage, which is measured on the same wires, is within specs with the sensor "UP". I'm not an engineer, but I would think that as long as the voltage was correct with the sensor "UP" then there shouldn't be a problem. Still scratching my head.
 

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"On the 5v circuit, I have 10.5 volts between the yellow/green - black/yellow wires (fail, should be around 5 volts) Both tests were done with the sensor disconnected and testing voltage from the harness."

I think the manual actually wants you to measure the input voltage with the sensor connected to the harness by using needle adapters on your voltmeter. Can you try this and see what you get?
 

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Discussion Starter · #8 ·
"On the 5v circuit, I have 10.5 volts between the yellow/green - black/yellow wires (fail, should be around 5 volts) Both tests were done with the sensor disconnected and testing voltage from the harness."

I think the manual actually wants you to measure the input voltage with the sensor connected to the harness by using needle adapters on your voltmeter. Can you try this and see what you get?
I'll have another look at the manual & re-run the tests. Heading out for the weekend, so I won't be looking at it until Monday evening. I will post the results
 

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I don't know this bike. I'd have to see the schematic, but WFO-KZ probably will know, he always does. ;)
Ha-ha. If only that were true. But thanks for the compliment.

I have the manual for his ATV but one year newer. They don't provide a schematic for the vehicle-down circuit, so that means dealing with the entire, rather complex, two-page wiring diagram. I hate it when they split the diagram into two pages.
 

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You got that right. As a former Kawi tech I rec'd factory training on important new developments in detail that the manuals never go into. But that was so long ago, I have forgotten most of it and it was all in the 1970's.
 

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The '70's were a great time for me. For me, it started falling apart in the early 80's. I was working on parts for the Hubble Space Telescope at Perkin-Elmer corporation. Everyone was so uptight and serious. ;)
 

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I only lasted 6 months there. The security was ridiculous, and the level that I was investigated, well, that opened doors for other places, like Sikorsky Aircraft. That place was stressful too. Working, and creating fabrication techniques that are still classified.
 

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Discussion Starter · #16 ·
"On the 5v circuit, I have 10.5 volts between the yellow/green - black/yellow wires (fail, should be around 5 volts) Both tests were done with the sensor disconnected and testing voltage from the harness."

I think the manual actually wants you to measure the input voltage with the sensor connected to the harness by using needle adapters on your voltmeter. Can you try this and see what you get?
I had a look at the manual. To test the 5V circuit; they state to have the positive tester lead on the harness side of the connector. It does not say to connect the harness to the sensor until you test the sensor output, which uses the needle adapters to back-probe the connector.
 

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Discussion Starter · #17 ·
I wish that I was able to share the service manual information to make sure that I am interpreting it right. It also has wiring diagrams for each circuit, but I don't have any idea how to share it. Most likely due to the fact that it is Copywrited material.
 

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Are you using the factory service manual? This is from the Kawasaki Factory Service Manual for a 2008 Brute Force 750.

Turn the ignition switch ON, and measure the power source voltage with the connector joined.

Input Voltage at Sensor
Standard: DC 4.75 ∼ 5.25 V
•Turn the ignition switch OFF
 

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Discussion Starter · #19 ·
Thanks for the replies. I checked the VIN# and found out that it is a 2005 model KVF750A. The manual that I am using covers KVF750A1 and KVF750B1. It was downloaded from the web., I can't find any indication of when it was printed.
Here's info the I copied and pasted from the manual:
This is for testing the 12V supply
e • Remove: Seat (see Frame chapter) Vehicle-down Sensor Lead Connector • Connect: Vehicle-down Sensor Lead Connector [A] (harness side) Digital Volt Meter I. Connections to Connector (12 V circuit) Meter (+) → Connector BR Lead [C] Meter (–) → Connector BK/Y Lead [D] • Turn the ignition switch ON, and measure the power source voltage. Vehicle-down Sensor Power Source Voltage Standard: Battery Voltage • Turn the ignition switch OFF. If there is no battery voltage, check the following: Main Fuse 30 A Ignition Switch Wiring for Vehicle-down Sensor Power Source
This one is for the 5V circuit
II. Connections to Connector (5 V circuit) Vehicle-down Sensor Lead Connector [A] (harness side) Digital Volt Meter Meter (+) → Connector Y/G Lead [E] Meter (–) → Connector BK/Y Lead [D] • Turn the ignition switch ON, and measure the power source voltage. Vehicle-down Sensor Power Source Voltage Standard: about 5 V • Turn the ignition switch OFF. If there is no standard voltage, check the following: Igniter Wiring for Vehicle-down Sensor Power Source Vehicle-down Sensor Output Voltage • Remove the vehicle-down sensor (see Vehicle-down Sensor Removal). • Connect the vehicle-down sensor [A] to the connector of the harness. • Hold the sensor almost vertical with the arrow mark pointed up. • Connect: Vehicle-down Sensor Lead Connector [C] Digital Volt Meter [D] Needle Adapters [E] Special Tool - Needle Adapter Set: 57001-1457 Connection to Connector (5 V circuit) Meter (+) → Connector Y/G Lead [F] Meter (–) → Connector BK/Y Lead [G] • Turn the ignition switch ON, and measure the output voltage with the connector joined. Vehicle-down Sensor Power Output Voltage Standard: 0.4 ∼ 1.4 V (with sensor arrow mark pointed up) • Tilt the sensor 60 ∼ 70° or more [H] right or left, and measure the output voltage. ○The time lag is from 0.5 to 1 second. Vehicle-down Sensor Power Output Voltage Standard: 3.7 ∼ 4.4 V (with sensor tilted 60 ∼ 70° or more, right or left)
 

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Discussion Starter · #20 ·
I'll have another look at the manual & re-run the tests. Heading out for the weekend, so I won't be looking at it until Monday evening. I will post the results
The 5V circuit test and the sensor output test are both done with the yellow/green and Black/yellow wire. With the sensor disconnected; I have 10.5V. With the sensor hooked up and back-probing the same wires, I have .732V (sensor pointed up). If the sensor is tilted, the voltage on the same wires is 7.5 - 8.5 volts
I also unplugged the igniter to check the continuity of the yellow/green wire which was good. Also there was no voltage on the yellow/green wire with the key ON (the entire plug was disconnected from the igniter) I think maybe I'll remove only the yellow/green wire from the igniter connector to test for stray voltage
 
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