I'm stuck waiting a week for the service manual for this ATV to come in. Till then - I'm slowly using meatball diagnosis to rule out each component I can.

I've got a fresh battery and checked all the fuses.
I took the kill switch apart and confirmed it was in good working order - not shorting unless in the off position.
I checked for voltage at the primary coil and it has ZERO.
I checked for proper grounding at the coil and it is fine.
I removed the CDI unit and checked each contact of it's plugs for any voltage coming into the CDI unit. All were zero except one which showed 0.17vdc when the key is on and the neutral light on(yes - it's in neutral)

So thats where I am - I'm thinking the cdi isn't getting proper voltage but I don't know where to look upstream next.

Could one of you fine fellows help me out with any info on what to look at next?
This ATV is a cream-puff w/little wear on it in all these years(think old-man w/farm).

I'm jonesing to ride it and return it cosmetically new condition - but I gotta hear it run!!!!


-Randy

 

When you get your manual make sure to check the pickup/exciter coil resistance. I don't remember what year it was, but there was a problem in that there was no spark while pushing the start button but would spark for a split second as soon as the button was released. If I remember correctly the problem was the CDI, I would have to check to confirm this. It may be something to look for if everything else checks ok.

 

Hello, I was wondering if You figured out Your problem yet? I am having a similar problem. I can't say for sure if it's the same part causing the fault or not. I'm going to My local library tomorrow to get a manual. I was wondering if You could let Me know what was wrong with Yours when You figure it out? I'll post a reply when I get Mine fixed. Thanks

 

I've learned a bit....
Looks like my problem is the coil....at least - I can confirm that the coil tests as bad at this point.
This is after I let the smoke out of the clutch diode experimenting w/o the manual. It's $15 from Honda but a trip to Radio Shack w/$2 will fix it.

I've got the wiring diagram scanned but it's for a 1988 model here:
http://www.linearrow.com/main/trx300fw1.jpg
http://www.linearrow.com/main/trx300fw2.jpg

I'll be happy to scan one of the others if you tell me the year.
Do any of you guys know the purpose of the clutch diode on this ATV? Since the clutch action is automatic(shift-lever activated via cable) - wtf is it for?


Mine smoked pretty good when I applied 12vdc to it. Hope it didn't cook the CDI too [img]i/expressions/face-icon-small-sad.gif[/img]

 

Here is a PDF wiring diagram from the Honda PDF shop manual ... If you need the ignition section post your email or PM it and I will email you the section ..

http://s5.uploadline.com/line/955981...AX_21.pdf.html

 

First - THANK YOU for posting the pdf. Information is king.

Since you obviously are an expert - do you think I damaged my CDI(assuming it was good) when I put 12vdc to my "clutch diode" and it smoked?

I've got a replacement - but I notice the wire coming out the other side of the diode goes straight to the CDI. It was only hot for a second or two but it got hot enough to melt the diode and the wire to it from the solenoid.

I would appreciate any clarification you might bring to how the ignition system works w/respect to the solenoid. I'm familiar w/basic ignition operation but I can't figure out what I did wrong to burn the diode.
There are two wires coming out of the starter solenoid(besides the in/out of the big battery cable).
One is for the starter button and the other goes to this diode and interconnects with the neutral light etc etc...
Where is the input power for the CDI? It looks like it provides power directly to the coil but I can't find any voltage going in other than what I thought came through the diode.

 

I got a manual from the library yesterday, I tested My coil and a coil off a parts bike, they both tested the same. The manual said there should be resistance between the two primary terminals, My ohm meter read zero, so I bought a brand new coil from My Honda dealer today, it reads the same as the other two used ones I have. The manual I have is a clymer I don't know if it has as detailed info as a honda manual. This is getting frustrating. I'ts twelve degrees here so I have to get a fire going in My garage and wait an hour for the garage to warm up, I hate to work on this thing and not get anything accomplished. Dan

 

Mine tests as Zero ohms too...Thats why I'm thinking it's bad. If yours is the same maybe not....

I do have a cheapo meter so maybe thats what's up.
I'll have some resolution to my problem in the next week or so - I got a complete wiring harness w/all the components off ebay for $40 shipped.

 

That's what I did, (buying harness off eBay) the only thing that didn't come with it was the coil. You got a lot better deal than I did, I paid $91.00. With this manual I've tested everything it says to test and the only thing I've found not working is the oil temperature sending unit. I don't know if that will make it have spark or not? It seems kind of odd if that could be My problem. I talked to the guy with the parts bike today and asked if He'd sell Me the whole thing, He said He needed a week to think about it. I bought this bike for $175 and was told it just needed the CDI & alarm boxes. I think He saw Me coming. The back tires wouldn't hold air for more than 5 minutes, $120 on new rubber today so I can roll it around anyway. I think I would have been better off passing on this deal.

 

I wouldn't say it was a bad deal - the parts for this model are cheap and available and it's a damn good design. I bought a 1994 2wd version New and got all my moneys worth out of it many times over. Once you find the problem you are done.