Which CDI unit for my '88 TRX 300 ?

So my new CDI unit arrived, only a week or so after ordering it. First thing I noted was how tiny it was! Its about 3/4" smaller in length and narrower too than the original. It came with new plugs but the colours dont match.

So I excitedly plugged it in and still no spark. I'm not upset as I still dont know whether its that, the regulator or the coil. I'm awaiting those other bits. I did query the seller as to why its so much smaller and is it actually the right part. They coulnt find out info and are going to refund me. So I might try another cdi but this time select a seller that deals only in bike parts etc. Or maybe get a slightly more expensive item from a reputable seller on Ebay. Any recommendations welcome

I also have query about my neutral switch. I am wondering if it somehow disables the spark?

I have followed the wiring diagram and can see how it allows the bulb to light and the starter to turn over, which it does fine. However the Honda manual states two different setups- '88 and after '88 to do with both the neutral and the reverse switches. But what its states should have continuity or not conflicts with what my Haynes workshop manual states.

Its all getting a touch confusing so any ideas or pointers would be great.

Plus I have seen a 'reverse/neutral switch hack mod' mentioned a couple of times. What is this?

Here 2 help said:

Also, the regulator has no effect on spark.

Click to expand...

Ahh I wasn't sure. In the wiring diagram it does show a feed to the CDI split off from one of the three yellow alternator feeds. I had also read about this factor in an earlier thread, actually the same thread I quoted you from at the start of this thread. See it pasted below..

Flyingfreeman wrote....

"The answer to your question is one the three leads from the Stator is wired in Parallel with the voltage regulator and the CDI (this is the link between the CDI and the Voltage regulator).

Apparently, at least one of the Diodes in my Regulator / Rectifier is bad affecting the AC current from the stator which feeds the CDI. This is how the Voltage regulator can affect the ignition system. (I did get some different readings between the 3 terminals on the voltage regulator that the stator leads connect to which would have led me to the bad regulator). The Honda Factory Service Manual does not indicate that the Voltage Regulator should be tested, nor do they provide any instruction on testing the Voltage Regulator on a non running engine (diode testing).

If you look at the wiring diagram and follow the stator leads, you'll notice the connection which goes to the CDI from this single stator lead between the stator and the Voltage Regulator.

There is a way to test the voltage regulator diodes (I've seen some posts about it), but I'm not certain that it is absolutely fool proof. And it is truly annoying when someone is asking for help with a no spark condition and guys post about testing the voltage regulator with the engine running... It's not running. That's why they are asking for help...

I never had a problem with the battery charging on this ATV, even when it started acting up. It would run sometimes, sometimes not. But the battery was always fine which would lead you to believe there is no reason to suspect the voltage regulator...

I just wanted to put this information out so that others that have this No Spark problem will hopefully see this which could speed their diagnosis and repair.

The dealerships have the advantage of being able to just plug in a new CDI and Voltage Regulator which only takes a few minutes to determine which is a problem as opposed to having to check every connection, ground, quick connector, and every device that can be tested with a multimeter before buying a replacement part.

If you have a no spark condition and everything tests good, and you've replaced the CDI, DON'T OVERLOOK THE VOLTAGE REGULATOR. IT CAN AFFECT YOUR IGNITION SYSTEM AND CAUSE A NO SPARK CONDITION."


I'm not sure how the feed might affect the CDI other than the CDI needing a separate signal from the alternator to say that the engine is turning over and allow spark?
I've ordered a regulator anyway- just in case and potentially useful to have as a spare

Oh hey. This thread...

I'll just pop back in to say that after ongoing intermittent faults and never really having a strong spark we recently replaced the regulator and the cdi with new Chinese items (both from sellers with good feedback etc) and it's worked a treat. Really good spark! Instant starting and it idles much smoother now!

Because I was not sure if it was the regulator not working consistently and possibly creating voltage spikes that finished off the old cdi unit I did not want to test the new cdi with the old reg in place and risk damaging the new cdi. So I'm afraid that without this the singuling out of either unit I'll never know what was part was faulty but I do suspect it was always the regulator that was the cause.

Here's a link to the cdi unit I bought. This one was the same size and of a similar weight to the original Honda unit-unlike the previous smaller lighter slightly cheaper one I had bought from China.

NZ$ 25.59 26%OFF | For Honda TRX300FW FourTrax 4x4 Red CDI Box Ignition Module Unit For Honda TRX300 FourTrax 1988-1993 FourTrax 4x4 1988,1990-1993

Alex

You are correct - Honda does indicate which pin is for what input - only 4 pins are required for spark: battery, ground, pulse and coil output.

Best to find another TRX300EX and find what each pin is assigned to

Stator yel/wht is for reverse speed limiting - it's just an input to read RPM

Early 400EX ignition - BTW, 400EX is AC ignition while 300EX is battery ignition

Ok - The 4 wheeler is a 250X - motor long gone....It came with a 300EX Motor ~ 99-01???

I was told it was running when pulled - but the kids can't can't get it to run....So I am piecing a bunch of stuff to try and get it to work - How hard can be right????

The wiring harness I have is from a 300, but it was cut to eliminate the Neutral and the Reverse box...safety stuff.

I think it got fried trying to splice in the locations as seen in the attached picture ( I think 5 is not to be used in a DC configuration) - I just read this....

I was thinking my best route would be a 400 because they don't have reverse and the safety DCI box....But I am at a loss...It can't be that hard???

Well - too every one that has read these past comments and to everyone who is the EXPERTS - most people will tell you it can't be done....sure go to school and allow your training to lead the way...

That's not good enough for me...Its called Trouble shooting - Sure DIAGRAMS can help, but factory does not tell you everything. (input to CDI box is not called out).

Its it running better then any stock 300's I have seen...

To every one that wants to know you can make your own wiring harness it is easy...Don't let the SMART People tell you it can't be done...

You Need an Exciter wire - 2 grounds, coil output.....Standard connection for the (4) plug - the (2) plug the Power is opposite what the Diagrams say DO NOT put power in the Pin #6 Slot....put switch power only in #5...

Bike runs great....

• use a CDI box fits the TRX300 Fourtrax 1994 1995 1996 1997

30410-HM5-505 or 30410-HM5-671

"DO NOT USE THE 300EX BOX"....

30410-HM5-505 CDI Box Compatible with TRX300 TRX300FW TRX400 TRX 300 400 Fourtrax FW Foreman 1994-2003

I Made sure I had Good Ground from Battery to Frame - Frame to Motor - I grounded the Green and white out of the Alternator to the Frame and the Coil Mount tab #3/4....You then put the Trigger into #1 the Blue and Yellow out of the Ignition pulse Generator...#2 is positive Coil.....
I ran the Switched Power to the Box into #5....I have been using Alligator clips trying to test connections - the #6 accidently fell off from the 15 amp fuse power lead - BINGO BANGO SPARK!!!!!

DO NOT USE #6 connect it to "AIR"