I have had this 300ex for a couple of years, and it has never let me down, until last week. We were riding all day, and I pulled it straight up and it fell on the left side into sand. The bike stalled. I put it back down, started it went about 50 ft, and then killed the bike w/ the kill switch. After this I could not restart it. (7 miles from the truck too)

In the field we assumed it was the kill switch because of the fall. We disassembled the swithc and manually jumpered the wires to repliate what the switch says. Still no luck. We pulled spark plug out, and we are not getting any visual spark at all. We then towed it back with a strap the 7 or so miles and called it a day.

Yesterday I dug into this thing some more. I pulled the coil off of my 400 and hooked it up to see if the coil was at fault, It did not work. I rigged up the 300 coil to my 400 and it works fine. So coil is not the isssue. I have +12 on the black w/ white wire going to the CDI. After the CDI I do not have a peak voltage tester to see what is coming out. On my 400 When I hook up my cheapo digital volt meter I get something like 18 volts going to the coil. When on the 300 I get 0 untill I stop pressing the switch, and it jumps to around 6v or so for 1/4 of a second or so.

I tried my cdi from the 400 in the 300, but I am not sure if the wiring is the same. (They are physically different sizes, and the 300 has one more wire) It did not work. 300cdi in the 400 did not work either.

Does anyone know how to test the cdi? or what else should I look for? I have a fairly good understanding of electroncs and know how to use my meter.

 

Call a bike shop and see if you jumped the kill switch correctly. Try the switch from the 400 on the 300.....
Good luck, anyway.

 

sherlocktk, You did a good job explaining what you did.
Im not positive I can help, but ill try.
Its not a good idea to make the cdi want to fire....with out a load hooked up(spark plug). Just a reminder.
Seems to me the cdi is pretty dead simple and reliable, and I really doubt, that a crash is gonna wreck it. Id focus on the battery. Some batteries arent built very sturdy, and all it takes is a bit of a knocking around, and the plates can come loose or short. Have you load tested the battery? Some times, due to an internal short, theres enough voltage to operate the starter, but not enough juice to make the coil fire. You could try watching the voltage on the battery while cranking, if it drops below 10 volts, its needs charging and load testing.
Try jump starting, or bump starting. Just remember, if youre jumping from a car or truck, dont have the donor vehicle running.
Let us know what happens.

 

hondabuster

That is a good idea about the battery. I keep forgetting cranking a quad over is a lot less juice than my truck. And a dumb motor will run on anything while electronics are a bit more picky. I will try the jump start thing tongiht. At this point, I am willing to try the most obscure ideas. I know that jumping a quad is a bad idea from a running vehicle as 14v for a quad system is not good obviously. But thanks for looking out for me. I will update tonight or tommorrow morning on the results. If this don't work I am probably gonna get a complete elec system off of e-bay for about 40 bucks delivered, between all that I should be able to get this thing working. Whatever the result I will keep ev1 posted of progress.

Tim

 

K I was lazy the last week. Last night i tried the starter thing to see if it was an undervoltage issuel. Without jumper cables on just battery c power while cranking I got 9.4 volts. When not craning 12.5 or so. So I hooked up jumpers to my trcuk abttery, and while cranking went up to 11 but still no spark. I ordered a n electrical harness off of e-bay for like 40 bucks out the door. A quote on diagnoses was like 65, so I bascailly have all the parts I dont; have any way of testing in duplicate now. Hopefully between all this I can get it working. I also picked up an electrical diagram for the bike, and I have confrmed all my switches are working as expected. Pretty much everything points to CDI. and I guess I will know once ups or whatever delivers the new one.

 

Thats quite a drop when the starter is going.
I think the cdi can be tested, but you need a honda dealer to do it.
One thing I dont think youve tried yet, but have you tried to bump start it? Just put it in 4th, key on,and have someone pull you along at about 7mph or so...itd be interesting to know if itll start then.
Thanks for the update.

 

I finally got my CDI in the mail via e-bay. Replaced it, and the bike now functions great. I guess they really do go bad. Besides that I changed nothing else.

 

At least you got it fixed,.... all thats left to do is ride it.