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No Fire! whits end

By mx369,
in YZ400F/426F/450F/450FX

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mx369

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2012 yz 450f. Went to start, nothing. Have another running yz 450f. Changed coil, rectifier, smoothing capacitor, ign box, spark plug cap, stator, and flywheel. New spark plug. Unplugged kill switch(left unplugged during changes). Got ohm meter and checked all this stuff with it. All good. Put non running bike parts on running bike one at a time. They all worked on running bike. Bought new wiring harness. Still no start. Looked at every plugin for bent or loose connection pin. All good. And checked with tuner. No codes. No fire at plug at all. Tried another new spark plug. Nothing!!!!!!!!!!!  Any ideas????

 

Did not change temp sensor, throttle position sensor, airbox sensor or the two pressure sensors

Edited by mx369
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Bass Mechanic

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No spark at all.  Did top end day before. But it fired and ran.    Checked cam timing twice after this started.

what does a compression test show?

are you seeing no spark at the plug? or are you assuming there is no spark with the plug installed because your not getting a bang?

if you've replaced the coil, the capacitor the only things left are the TIP coil in the alternator and the ECU

either that or your down on compression. since you did a top end you might re-check your valve clearance and or do a compression test.

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Bass Mechanic

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Put on new wiring harness last night.  All plugs checked.

i would look at the stator, ecu and if you can test that the coil is actually getting a signal from the ecu.

 

i assume if you swapped the coil you can eliminate the plug wire itself.

also its a long shot but you might check all your grounds. im sure the coil ground is hard to mess up but without that there is no path from the plug wire to get back to ground of the coil.

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mx369

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All parts checked for resistence by using Yamaha specs.  Then parts removed and installed on running spare bike. Only 1 ground wire on harness ( NEW harness).  Plug wire is attached to coil. Also new spark plug cap. I have changed EVERTHING except pressure sensors to a RUNNING bike and all worked.

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drtrcr400

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Sounds like it's time to get another set of eyes on it. You're obviously frustrated and not thinking straight. This is just a machine and if you've done everything as you've said the problem should have revealed itself by now. Time to have a knowledgeable friend or shop have a second look. Just my opinion, not trying to offend you.

Edit; I just thought of something and don't even know if it's a possibility but may be worth a look. Is it possible your plugging the coils primary side into the wrong harness plug? I realize this is likely impossible due to Yamaha generally using a different connector on almost each component. Anyways good luck!

Edited by drtrcr400
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mx369

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tried using the other bikes kill switch just to make sure it didn't HAVE to be there. There are a pair of plugs that are the same on this harness.  Both are for pressure sensors but they are marked #1 and #2. Checked running bike to make sure they are plugged to right sensor.

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Bass Mechanic

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tried using the other bikes kill switch just to make sure it didn't HAVE to be there. There are a pair of plugs that are the same on this harness.  Both are for pressure sensors but they are marked #1 and #2. Checked running bike to make sure they are plugged to right sensor.

do you know for a fact your getting signal from the trigger coil? have you tried to monitor the tuner and see if any rpm reading is present when the bike is kicked over? in monitor mode you should be able to monitor the other sensors as well. but i think on a YZ with no battery it may have to be running.

my guess is it has something to do with the power on this bike. how about the rectifier? does a YZ even have a rectifier? have you even plugged a meter into the stator coil and kicked it to see if your getting any AC power from the stator?

just replacing parts is not your solution. i bet if you start at the source of power you'll find your problem.

i think the stator is either disconnected behind the cover or shorted somehow. easy way to test that is to check it with a meter. if you have power there then follow the power through each connector intil it reaches it's destination.

so you have a wiring schematic you can post here?

ive been into electronics since i was 8 years old.

i know i can solve this problem for you.

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mx369

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just plugged in Yamaha tester. no codes. It does not have a battery in system. I have spark plug out. kicked over by hand and got a reading of as high as 450 RPM.  Stator is plugged in. I have tested it by Yamaha instructions. Tests good. I have removed the whole stator( built in to side cover) and installed it on another running YZ450 I have. Fires right up. Installed running 450 stator system on non running bike. No fire.

I had access to some new Yamaha parts( coil  smoothing condenser and wiring harness)  Have installed these for testing. No fire. All old parts and new parts test the same.  Only difference is between the TPS from bike to bike but still in specs.

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