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Discussion Starter · #1 · (Edited)
Recently paid a well-respected local mechanic to do a triple-bypass on my 650T. When I got it back, it's running like crap. She starts and runs but runs rough and doesn't want to rev.

The ECU error code points to the Crankshaft Position Sensor. I have checked the sensor and the Ohm test is within the factory service manual specs. I also checked the speed sensors and they both checkout ok as well. This is the stock speed sensors, so I don't think the polarity is wrong.

I have checked all the connections and, so far, everything looks good.

Anything else someone could recommend checking before I start pulling the motor out of her (again) to see what's up?

Bringing it back to the mechanic is not an option at this point as I no longer trust him in any way.

Thank you in advance for any assistance.
Darren

 

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There are two sensors in the water pump housing. One probably failed just from being disturbed during the work. The bike will run like crap with one sensor.

They're easy to replace without removing the engine. Also very inexpensive.

I wouldn't blame the mechanic. Cascading problems go along with owning any 40 year old vehicle, especially something as complex as a CXT. This is why no dealerships and most bike shops won't touch an older bike.
 

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George - do you understand why the ECU would be giving me a cam sensor error though?

Trying to wrap my head around that.
What error code lights are you seeing on the ECU?
We need to determine if this is a SPEED sensor (Ne) or a CRANKSHAFT angle sensor (Ns) error?
You mentioned speed and cam sensors which are different names for the same thing.
If it's a speed sensor, the ECU will tell you if the left or right has failed by reporting a specific code.

The fact you have some sort of error code leads me to believe your timing is NOT off a tooth.

Not saying it can't happen, but I've never heard of someone having issues with the Crankshaft sensor. Speed sensor failures are very common. The water pump mechanical seal weeps coolant which eventually destroys the Ne sensors.
 

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Discussion Starter · #6 · (Edited)
Lights 0 and 3 are blinking. According to the FSM, that is crankshaft angle sensor (Ns). I mentioned the Ne sensors just because I had read many posts where bikes were having similar symptoms and the consensus was to check those. (Also, I corrected the original post which did say Cam Position Sensor - should have read Crankshaft Angle Sensor).

I spoke with Greg Goss today for about an hour. He built this bike initially. He feels like the mechanic may have pinched the crank angle sensor wires when he put the motor back together. His advice was to pull the motor and check it out.

I trust Greg a shit ton, but always open to an option that would NOT involve pulling the motor :). So if you have another suggestion.... :)

Thanks everyone.
 

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You threw me off when you mentioned speed and cam in the original post...was hoping that's all it was. Yeah, crank angle is going to suck as it all needs to be torn down again. :mad:

What ohm reading did you get on that sensor? If it's within spec (85 to 115 ohms), I would be really hesitant to start pulling the engine. For the heck of it, check each sensor wire to ground, that'll show if it got pinched and shorted.

One time my 650T left me stranded, the ECU kept reporting a bad sensor, yet the sensor was fine. Should have also run in limp mode, but didn't. Ohmed out the wiring all the way to the ECU pins and all was fine. Turned out to be a bad ECU.

Where are you located? We're spread pretty thin, but I'm sure a few of us would be willing to help out a local.
 

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Discussion Starter · #8 ·
I don't remember the exact number on the reading, but it was within specs outlined in the factory service manual.

I am in Louisiana.

I plan to pull off the fairings and tank when I get back from Barber Vintage and starting to go over all the wiring. There are a few other electrical issues (gas gauge isn't working, blinkers are wired wrong) that makes me suspect the "mechanic" may have taken some short cuts when he put it back together.

Thanks George.
 

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I ran into a similar scenario just a few days ago.
I had a code showing 3,0,W, indicating I had an (Ns) crankshaft sensor issue.
I checked the resistance of the Ns sensor and it measured in spec.
The only thing I had changed were the engine speed sensors , (Ne), so figured that it was related to the Ne speed sensors.
So I looked at my old pics when I refurbed the sensor rotor, see second pic.
Notice the blue and blue/white wires are on the right hand side, and the yellow and yellow/white wires are on the left hand side.
Now look at the electrical schematic, it shows that the Blue and Blue/White wires go to Left hand Ne sensor, and the Yellow and Yellow/White wires go to right hand Ne sensor.
So once I found this I realized that my left and right were switched.
To correct this, all I had to do was switch the Blue/White wire (Left Ne sensor) to the Yellow/White wire of the 4P connector and the Yellow/White wire (right Ne sensor) to the Blue/White wire of the 4P connector.
Now the bike starts and runs no problem.
I suggest you trace the Blue and Blue white wires with a multimeter back to the ECU pins, 7, 25, and 8. This will tell you quickly if your Right and Left Ne sensors are reversed.
There was also a discussion on the forum that replacement Ne sensors are polarity sensitive, although I didn't have this issue.

Rectangle Font Parallel Number Engineering
Output device Gadget Font Personal computer Flat panel display
 

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Hard to know what exactly your mechanic did or did wrong, spend some time with your multimeter and go over every electrical connector you can get to and trace back wires through connectors and to ECU, especially the coils, Ne sensors, spark units, etc.
It took me a good number of days to methodically go through it all, but of course my bike is stripped down and easy access. Now I know the bike better than ever.
There is a post here for ECU pin layout, a great guide.
 

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So once I found this I realized that my left and right were switched.
To correct this, all I had to do was switch the Blue/White wire (Left Ne sensor) to the Yellow/White wire of the 4P connector and the Yellow/White wire (right Ne sensor) to the Blue/White wire of the 4P connector.
Now the bike starts and runs no problem.
Did your bike actually start but just run poorly like the OP's? When those wires are swapped, the ECU shouldn't see a run signal. The bike starts (because of the initial fuel pump prime when the key is turned on) but dies out after only a few seconds due to no power to the fuel pump.
 

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Bike starts and runs, does not die out, and no ECU codes, the bike has only been idling for a short time, but found an oil leak, so need to figure that out before running the bike.
 

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Discussion Starter · #14 ·
UPDATE: Checked the speed sensors to ensure they were not swapped L to R and R to L. Did this by un-pinning the wires from the plug and swapping them out. It got worse when we swapped them, so I am guessing the mechanic didn't swap them L ro R and R to L. I drained all the fuel out the tank and ran about a quart of 1/2 and 1/2 fuel and Seafoam. That seemed to make the bike idle much better, but it still won't rev like it's supposed to. Also still have the W 0 and lights on the ECU.

Went back through all the sensor and double checked on ohm readings and they all check out fine.

Any other thoughts?
 

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Gas Composite material Electrical wiring Cable Cleanliness

This is how it should be in the connector. Yellow/white and blue/white on the right and yelow and blue without stripe on the left.
Yellow at the connector lock side.
But........if the mechanic changed the wires inside the other way around then you have to search further

Which lights are blinking on the ECU. W is always on and others can blink. This is important to know where the fault is.
 

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Discussion Starter · #20 ·
I de-pinned the plugs again and wired it according to dutchturbo's picture and it won't even start. It starts and runs (horribly) when wired to the factory service manual spec (pic below)

Also also tried to swap the grounds to see if they were reversed and it wouldn't start that way either. It only starts and runs in this configuration.
 
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