I'll try to help you as best I can

First of all, the 400EX does not need a battery or rectifier to make spark - the battery is there to turn the engine via the starter motor and the rectifier is there to turn AC into DC to charge the battery

Therefore the ignition system consists of the stator, pulse generator, the CDI box and the coil

Coils seldom go bad, but the plug cap does go bad more often than the coil - stators have the highest failure rate followed by CDI boxes and then pulse generators

To begin with, you have to eliminate the "kill" wire - it's the black wire with the white stripe - connect that wire to ground and the spark goes away

If that does not fix it, then check all the connections - a bad ground at the coil or at the motor mount points (common on powder coated or freshly painted frames) will kill the spark also

The alternator is a 3 phase unit - 2 phases are used for charging the battery and one phase is used to excite the CDI - if the engine does not have a good ground, the stator does not have a complete circuit and the CDI box needs a good ground on the green wire with a white stripe

Hope this helps a bit

 

Hello I’m having the same problem with my Trx400ex I bought everything brand new wire harness,new Cdi,New ignition switch,New pickup coil,new solenoid,new spark plug,new stator,relay rectifier and I’m still not getting any spark where was the black and white wire that you was talking about that if it’s grounded it doesn’t let the spark plug spark ? Or what should I do ??

 

Is there supposed to be 12 volts going to the CDI box? If so, I am not getting anything even when the motor is turning over. The Black/Red Wire is the one I am testing which is on the two wire plug.

 

No - there is not 12 volts to the CDI box

You need a peak voltage tester to check the stator output voltage between the black/red wire and the green/white wire - with the engine cranking (spark plug out) you should get 100 peak volts

 

I have 2013 model no spark after unloading from pickup. The engine was turned backwards.... From that. Has no spark now

 

Got a 04 400ex that has no spark. Been trying to figure out what is wrong with it for about 6 months now. I have replaced the stator, cdi, rectifier, the stator pickup, and coil. I have stripped my wiring harness to check if there were any broken wires. Nothing wrong with main harness or the start/kill/light switch that I can see. Tried a few things I've seen on forums. I don't know what else it could be. I'm stumped and I have worked on multiple 400exs and never have had this problem before. If anyone could help me out, that would be great.
Thanks, Cody

I think i ended up with your quad.

 

I take you are having a no spark issue?

 

The spark plug grounds to the engine and the coil grounds to the frame - if the connection between the engine and frame is lost, so is the spark - of course new parts can have their own faults. I have restored spark by making my own wiring harness eliminating everything except the connections necessary to produce spark.

In the above diagram is the bare bones connections to produce and kill spark - first eliminate the kill function by disconnecting the blk/wht wire. Now use an ohm meter to verify all wiring connections especially grounds - actually start with grounds, when you have verified all the components have good grounds, verify continuity of the wiring from each component to connected component. Verify continuity of each testable component. Finally, get a peak voltage tester and verify the voltage output of each component.

Now although all the parts you say you installed new are available from Honda, I seriously doubt you spent $835 for parts in your quest to fix the issue. I suspect you bought parts from Amazon or Ebay, so you have a collection of Chinese counterfeit parts on your vehicle, so this complicates matters because instead of troubleshooting the parts that were working prior to the failure, you decided to throw parts at it to see if it would stick.

Now the one part of the ignition system you did not replace was the flywheel. I have seen flywheels come loose and the woodruff key that positions it on the crank shears throwing it out of time. Before you started throwing parts at it, did you verify the position of the flywheel with the engine at TDC? You are going to feel really silly if you find out the key sheared and the timing is off.

Compression, fuel and air in the right ratio going in and coming out, spark and spark at the right time and the engine will run, but if the flywheel is out of sync with the CDI unit, there will be no spark, weak spark or spark at the wrong time and the engine will not run. It's actually rather common for a running engine to lose spark suddenly due to the flywheel being out of time.

Let me know if this gets you any closer to getting spark back. I might have to guide you through the peak voltage tests to restore spark.

 

yeah I threw some Chinese parts in there to see if I got it running but I don’t know how to check the wires with the voltage meter I will need help and yes the timing is good but when I put the new parts in I didn’t check if my flywheel was at TDC I just put the parts in and cranked it the plug gave me spark at first but then after no more spark and engine made a weird noise but can you help you on how to do the voltage test and how to check if my flywheel is in good condition and TDC? Thanks!!

 

One step at a time: Remove the spark plug, remove the timing inspection cap and crankshaft nut cover from the LH engine cover (alternator cover) - using a plastic or paper drinking straw position the piston at TDC - the straw is used to insert through the spark plug hole and feel the position of the piston - turn the crankshaft in a counter clockwise direction with a socket on a t-handle or breaker bar - when the piston it at TDC, the straw will begin to move downward whether the crankshaft is turned either way from TDC - you should see the T mark in the inspection hole when the piston is at TDC - if not, turn the crankshaft clockwise until you see the T mark - if the mark shows up within 90 degrees of rotation it is an indication that the flywheel key has sheared throwing the timing off far enough to lose spark. If the T mark is in the inspection hole at TDC, then we will move on to testing the ignition system.

 

Okay so I checked it and it was good at TDC so next step is to test the ignition system how do I do that?? thanks for the help too

 

You will need to buy or borrow a multimeter with a peak voltage function - first test the pulse coil for continuity and if good, check for peak voltage output - typical is .7volts (7/10 - seven tenths of a volt) with the engine cranking normally.

The pulse coil just tells the CDI unit when to fire the plug

The exciter coil has to charge the CDI unit - the exciter coil should generate about 100 volts peak and the voltage to the coil should be about 100 volts also. If the exciter coil has the proper output and the voltage to the coil is low, the CDI unit is the culprit - if the voltage to the coil is OK, then the coil or the spark plug cap or the spark plug are the problem

 

Okay so those are the only things I will be testing with the multimeter? I also have an extra coil incase this one won’t give me the voltage it supposed to and one question is it okay for me to keep the Chinese Wire harness with the rest of the parts would the bike start even tho they Chinese?

 

A leaking head gasket will not cause a loss of spark, but it will keep the engine from running. It needs a minimum of about 110 to 120 psi to start - under 100 it would have to be pull or push started

 

Ohh okay I will try to fix that leaking head gasket problem as well to i will keep you updated if the bike does start I will text you for help if i need. thanks for helping.

 

The plug does not have to be tight for the engine to run, but if it's not tight enough to prevent leakage, carbon from combustion might fill the threads and lock the plug into the hole. Get it running first and then worry about the plug later.

 

Okay so I’m getting spark now and fixed the stripped stud nut and torque all of the stud nuts to 32 foot pounds and brand new head gasket so no compression leaks out but I’m still getting 90 psi for compression. I’m pretty sure now it don’t start because of low compression what should I do to get it started other than push starting it??

 

@Cristofer631 @here to help this forum has been a great help with certain aspects of the diagnosis.

IM in the exact same predicament as chrisofer631 .. no spark changed parts ect

My crank and tdc is fine. Please can i have assistance on the testing of the exciter wire red and black wire would this need testing at the CDI or as soon as it comes from the stator .?

Thanks in advance
Ps trx 400ex
2004

 

IM in the exact same predicament as chrisofer631 .. no spark changed parts ect

My crank and tdc is fine. Please can i have assistance on the testing of the exciter wire red and black wire would this need testing at the CDI or as soon as it comes from the stator .?

Ps trx 400ex
2004

Testing the exciter coil - blk/red wire to ground - should test appx 45v peak - you need a meter with a peak voltage function or a PVA (peak voltage adapter) for a standard DC voltage reading

 

Thanks for the quick response. Okay so i have this multimeter (TIS 258 Digital Multimeter With Temperature Probe)
Unfortunately i dont think this measures peak voltage. Ill buy a adaptor. Ive dont a ac voltage check with the above multimeter, red probe on the black and red wire and the other to ground .. when i crank the engine i get 50acv
Ive checked continuity of all the ground points and all is fine.

Is there any checks i could be doing in regards to voltage checks with my current multimeter to dignose the issue before i buy a new meter.

thanks again

 

please see specs for multimeter

Thanks

 

Forgot to mention kill switch is eliminated.

Thanks

 

For that price it is for indication only, not going to be highly accurate and no, there is no peak voltage selection

 

Thanks for your message. Ill look at buying one asap .. what doed the peak voltage symbol look like. My understanding is that it gives a min and max output.. am i correct with this ?

 

Can't say for sure - each mfg. uses their own marking, but generally min-max is the indication for measuring transient voltages

 

Thanks for your response... ive now ordered a peak voltage adapter. Ive spend the whole day going through my wiring ensuring the issue has nothing to do with the clutch or neutral switch. They seem fine.(Found a wiring diagram online)

I noticed you said to check for continuity from the pulse wire. I guess the purpose of this test is to determine if the wire coming out the stator to the cdi is fully connected to the CDI with no breaks. No issues here

Im wondering whether the pulse wire is correctly gapped when i replaced the stator. I didnt recall seeing any room for ajustment they just bolted in.

Could i do simple resistance check when cranking the engine to see if i get a fluctuating reading from the pulse wires as it spins the crank

Lastly as im inpatient i tested the ac volts with my meter again on the red and black wire (exciter) And got a steady 70 when cranking

I know its not the proper tool but delivery for this is around a week.
ive also tested the black and yellow wire into the spark coil and the ac reading seem low. Does this seem normal.

thanks

 

Normally, I would say no, but if you use an analog meter set on the AC or DC scale and see movement of the needle it is usually a crude indication of a trigger pulse - then the only thing left is the CDI unit, coil, spark plug cap and spark plug.

 

Thanks for your help.

Ill wait for the adaptor and continue my checks.

Will update you very soon.

 

Hi,

So today my peak voltage adapter arrived.

These are the checks ive done so far
Exciter wire
Red probe on black/red wire
Black probe on green/ white wire.

Set the multi meter to dc voltage
My reading i got when cranking was 116.3dcv
I believe this is okay.

Next test i did was ignition pulse generator.
Red probe on blue/yellow
Black probe on green/white

From the front of the atv i get no reading when cranking 0.00

From the back where the wire comes from the stator i get 2.78dcv unplugged from harness and checks stator side)

Now i find this very odd. I have a new loom on the atv and have checked for continuity from the green and white wire going to the cdi plug to the plug on the stator all is fine.

Ive also check the continuity cdi plug and rear of the blue/ yellow all seems fine

Im not sure if 2.78dcv are correct but i definitely know that having nothing at the plug end by the cdi is wrong.

Any advice would be appreciated

Thanks

 

Quick update i now have dc voltage at the cdi socket at the front of the atv . Ignition pulse generator.2.78

Ive done a test on the yellow and black wire going to the coil and get nothing

So red probe on yellow and white wire

Black probe on ground.

Thanks

 

Quick update i now have dc voltage at the cdi socket at the front of the atv . Ignition pulse generator.2.78

Ive done a test on the yellow and black wire going to the coil and get nothing

So red probe on yellow and white wire

Black probe on ground.

Thanks

So what did you do to get the voltage to the front?

 

2 to 5 volts from the pulse generator is nominal (meaning what you are reading is good) - the charge coil generally puts out about 45v nominal, so that's good the last thing needed is about 100v from the CDI to the coil on the blk/yel wire to ground. If all that checks good, then it's most likely a faulty coil, spark plug cap, spark plug or the rare loss of ground between the engine and frame. If the electric starter works, then loss of ground between engine and frame is highly unlikely as a factor.

 

Okay so im not getting any voltage from the cdi to the yellow/black wire . Ive already replaced this units once in trying to fix the fault.. (i did use a aftermarket cdi at 80pound 109 dollars approximately on ebay) is there any other ways i can confirm if it is the cdi. Is there a cheaper box i could buy. Last thing i want to do is buy the cdi to find out its not that.



Thanks for your reply. Means alot.

 

Okay so im not getting any voltage from the cdi to the yellow/black wire . Ive already replaced this units once in trying to fix the fault.. (i did use a aftermarket cdi at 80pound 109 dollars approximately on ebay) is there any other ways i can confirm if it is the cdi. Is there a cheaper box i could buy. Last thing i want to do is buy the cdi to find out its not that.



Thanks for your reply. Means alot.

To discover i had no voltage on my black/yellow wire. I plugged the cdi back in to the harness and cranked the engine

The peak voltage was checked

Black wire to ground
Red to black/yellow.

Thanks

If the peak voltages are good going into the CDI, then the CDI unit has to be the problem

I don't buy from Ebay or Amazon - the part number is 30410-HN1-003 and it retails for $120 USD - I can buy for $80 new from Honda.

 

To discover i had no voltage on my black/yellow wire. I plugged the cdi back in to the harness and cranked the engine

The peak voltage was checked

Black wire to ground
Red to black/yellow.

Thanks