250sx help

[mark38090]

oage 14-2 in the manual, checking the CDI unit. Measure the resistance between the Bu/Y and G/W wire terminals. Standard: 290-360 ohms... the only problem is that there is no Green/White wire... CDI wiring diagram shows wires Bl/W, Lg/R, Bu/Y, G, Bl/Y, Bl/R. So, where is the phantom G/W wire at.

[Dirtcrasher]

There just having you check resistance to ground. If there isn't one, I'd just use the G or ground and check the readings. Whats the problem? I've rarely seen an SX electrical part go bad, it's always been a bad connection for me. I've owned at least 6 SX's.....

[mark38090]

I have no spark... I ohmed the coil and it's way out of spec... I found one on Ebay for less than $20...

[oldred95]

Whats the problem? Crank no spark? Happen all of the sudden? Has the bike sat for a while? If so, take the CDI off and slam it on a concrete floor or steel work bench a few times and plug it back in and check for fire. Something inside the CDI sticks and it stops working. Smack the hell out of it a few times and it works just fine again. My dad and I both have done that on probably half a dozen bikes so far, most of them being 300 fourtrax's and my TRX 125 did it a month or so ago too.

[Huffa]

Whats the problem? Crank no spark? Happen all of the sudden? Has the bike sat for a while? If so, take the CDI off and slam it on a concrete floor or steel work bench a few times and plug it back in and check for fire. Something inside the CDI sticks and it stops working. Smack the hell out of it a few times and it works just fine again. My dad and I both have done that on probably half a dozen bikes so far, most of them being 300 fourtrax's and my TRX 125 did it a month or so ago too.

:wondering Could I try that on a whole motor that does not run, just smack the hell out of it and slam it down on a concrete floor?

:lol: If only other parts would fix themselves that way too!! :lol:

[oldred95]

Its worth a try....


On my 125 it got to where it had a miss fire at WOT and starting slowly got worse and worse and finally one day it lost fire all together. I took the CDI off and smacked it about 5 times and got a very weak spark so I smacked it again probably 10 or 15 times and finally got a strong spark out of it again. I cranked it up yesturday with a nearly dead battery and it fired right up on full choke after sitting a month. It would have never done that before and it doesn't hat the WOT miss fire either.

[mark38090]

The problem is no spark... I've pretty much traced it to the coil being bad... Got one off of Eay for $12.00. Should be here next week... Then I'll start again.

[Howdy]

Check the ohm reading of the black w/red striped wire coming from the stator ( one lead on the terminal and one to a engine bolt ). Let us know what that reading is.
Howdy

[oldred95]

My money is still on the CDI.

[mark38090]

Thanks Howdy, I'll do that in the morning if the rain ever quits...

[mark38090]

Check the ohm reading of the black w/red striped wire coming from the stator ( one lead on the terminal and one to a engine bolt ). Let us know what that reading is.
Howdy

If the terminal is unplugged 0.392 . With the terminal plugged together 0.290. What does that tell me ?

[Howdy]

If the terminal is unplugged 0.392 . With the terminal plugged together 0.290. What does that tell me ?

It needs tested while unplugged. I don't quite understand the .392 reading. It should be in a whole number ( no "." ). According to the one I just fixed it should have around 200 ohms. On that one the stator was the culprit.
Howdy

[mark38090]

Howdy, between 280 and 290 while plugged in...

[Howdy]

Howdy, between 280 and 290 while plugged in...

You have to test the stator while it is not plugged into the wiring harness. You won't get a correct reading any other way. Are you using a digital ohm meter or a analog ( sp? ) one?
Howdy

[mark38090]

Howdy, I have a digital ohm meter and with the stator unplugged I have a reading of 322.5 ohms.

[Dirtcrasher]

It needs tested while unplugged. I don't quite understand the .392 reading. It should be in a whole number ( no "." ). According to the one I just fixed it should have around 200 ohms. On that one the stator was the culprit.
Howdy


I think he was just on the wrong scale. He must have been on 200K or something.

[mark38090]

Its worth a try....


On my 125 it got to where it had a miss fire at WOT and starting slowly got worse and worse and finally one day it lost fire all together. I took the CDI off and smacked it about 5 times and got a very weak spark so I smacked it again probably 10 or 15 times and finally got a strong spark out of it again. I cranked it up yesturday with a nearly dead battery and it fired right up on full choke after sitting a month. It would have never done that before and it doesn't hat the WOT miss fire either.

Is this something that keeps sticing or do I need to replace the CDI...

[Dirtcrasher]

Is this something that keeps sticing or do I need to replace the CDI...

Don't be like 75% of all backyard mechanics. They run out and buy a used CDI, Coil, harness and a new plug and it still doesn't run. Don't be a parts changer, be a mechanic. Unplug every dam electrical unit, get a good meter and test each part. If you get an odd reading, have someone test there's and compare. Your stator has more resistance than spec'd out. But at least it doesn't have zero resistance which would mean "open" or "broken wire" so I would check the rest of the pieces. Then you have to ohm out the harness and check the switches and grounds. If someone who has found electrical problems would give you a hand, you'd see that it's not that bad.

Yes, it's much "easier" to just start changing parts and guessing. But, you won't learn anything and could cost yourself alot of cash.

95% of electrical failures I've had were bad grounds, crappy contacts and broken wires. Thats every ATC,ATV, dirt bike, lawnmower or automobile I have owned and repaired in the past 20 years.


Forgot to mention, lots of electrical problems are cause by previous owners or "hacks". Look for lots of electrical tape or bulky harness areas and untape them to locate a potential problem.

[mark38090]

I've checked everything in the harness, checked the on/off switch and ignition. Whenever it shuts off I can just tapped on the cdi and it will start right up. Everything else checks out fine, the old coil was bad, I had it checked at the local bike shop. That was $12.00 well spent.

[Dirtcrasher]

I've checked everything in the harness, checked the on/off switch and ignition. Whenever it shuts off I can just tapped on the cdi and it will start right up. Everything else checks out fine, the old coil was bad, I had it checked at the local bike shop. That was $12.00 well spent.


So you had a bad coil and bad CDI all at once??


As for the CDI, that sounds like a bad connection. Certainly can't be junk if a little tap gets it going. Possibly inside that CDI there is a soldered joint gone bad. If your gonna junk it, carefully cut it open and maybe it could be resoldered. I'm fairly certain it is a solid state ignition, it doesn't have points or moving parts so it is worth a shot.....:w00t:

[mark38090]

Thats what I was wondering, It's not completely shot so I wonder how hard it is to fix?

[mark38090]

Got my new CDI today, plugged it in and it fired right up...