KX250 help

[-df-]

Hi,

I have a problem with my KX250H. I've asked here before...but now have new information so thought I'd see if anyone knew what was going on as I'm stumped.

When kicking the bike over I get up to 20v AC out of the CDI unit wire going to the coil, and also about the same coming out of the coil (and tried another one that was lying around and got 0v AC out of it) so figured the coil was stuffed. I got a new (2nd hand) coil from a wrecker and tried it just now...and here's what happens.

coil not bolted up to frame: (so no earthing) up to 20v AC going into the coil, and about the same coming out (not sure what the volts should be but got told times it by 10ish...if someone could tell me that would be great).

Coil bolted up to the frame (so its getting earthed): up to 20v AC going in, nothing comes out the other end 0v (set my MM to 750v and 200v both AC).

Is this coil also stuffed or is something else going on? I haven't got the money spare at the moment to take it to the shop as I'm looking to by another road bike so have to fix it on the cheap.

any help would be awesome as I'm lost here.

Cheers,

-df-

[davereid]

The coil should be bolted to the frame to get any kind of useful readings from it.

You wont be able to measure the HT (Spark Plug Lead) output voltage with your meter.

This voltage is going to be around 25000 volts, and would ruin your meter very quickly.

As a quick test the primary of the coil should be 0.28 to 0.34 ohms, and the secondary (Spark Plug Side) 7-10 ohms.

[-df-]

The coil should be bolted to the frame to get any kind of useful readings from it.

You wont be able to measure the HT (Spark Plug Lead) output voltage with your meter.

This voltage is going to be around 25000 volts, and would ruin your meter very quickly.

As a quick test the primary of the coil should be 0.28 to 0.34 ohms, and the secondary (Spark Plug Side) 7-10 ohms.

Thanks for replying so quick Dave.

I'll go test the coil now and see what it comes up with.

maybe the MM is overloaded and ignoring the value...might go put the tank back on and kick it over a few times and see what happens if the values come back correct.

THANKS!!!

[-df-]

well...I know now that I don't know how to check the primary and secondary parts of the coil...are you able to explain that one to me DaveReid?

I tried kicking her over...but now my legs are dead...and I must have flooded her as petrol started to come out from the overflow.

I'm off to buy another spark plug JUST incase the new one I got when I purchased the bike (in its current state) has shagge itself (altho its never run so can't see how).

if this doesn't work I think its time to sell her to someone that knows what they are doing...and put the money towards the new road bike.

EDIT: Got new plug...still no luck (the old one was the wrong type...didn't have a resistor on it...must have given me the wrong one).

[davereid]

Very Easy to test.

1 - Meter on OHMS range

2 - Black lead of meter connected to earth on bike, or if the coil is out, to the earth lug on the coil.

3 - Then the wire that goes to the CDI is connected to your meters red lead. This will give you the primary value. It may be hard to see such a low value if your meter is tragically low cost.

4 - Then move the meters red lead to the wire that goes to the spark plug (big thick wire). This should be easy to read.

This is a basic test and won't find some coil faults, but it should help.

p.s. You have checked the obvious - neutral switch - engine stop switch, etc etc ?

[-df-]

Very Easy to test.

1 - Meter on OHMS range

2 - Black lead of meter connected to earth on bike, or if the coil is out, to the earth lug on the coil.

3 - Then the wire that goes to the CDI is connected to your meters red lead. This will give you the primary value. It may be hard to see such a low value if your meter is tragically low cost.

4 - Then move the meters red lead to the wire that goes to the spark plug (big thick wire). This should be easy to read.

This is a basic test and won't find some coil faults, but it should help.

p.s. You have checked the obvious - neutral switch - engine stop switch, etc etc ?


Cheers for that, just tested it...and...well...I just can't beleive it...

I had 2 coils (original one from the bike and another 2nd hand one) from the guy I purchased it off, both are showing infinite resistance...bugger...tested the new one I got...exactly the same...

The primary was showing 0.9ohms and infinite for the secondary.

I just can't beleive that all 3 are shot...are these the sorts of things that blow very easy? I just don't want to spend $180 for a new one to find out its not the problem.

Again cheers for your help.

[davereid]

It certainly seems unusual to have 3 coils fail the same way !.

What you are measuring is the continuity of the secondary winding of the coil. An open circuit or a short is generally indication of complete failure !.

Why not invest $3 in a post-it bag, and post me a coil, or two. I'll test em, and let you know, just in case you have botched up the test. It will also cost you a beer if I meet you at a rally or whatever.

Courier - Scooters Plus, 7 Hokio Beach Rd, LEVIN

[-df-]

It certainly seems unusual to have 3 coils fail the same way !.

What you are measuring is the continuity of the secondary winding of the coil. An open circuit or a short is generally indication of complete failure !.

Why not invest $3 in a post-it bag, and post me a coil, or two. I'll test em, and let you know, just in case you have botched up the test. It will also cost you a beer if I meet you at a rally or whatever.

Courier - Scooters Plus, 7 Hokio Beach Rd, LEVIN

Definatly already owe you a beer, but going to admit defeat and take it to the shop and find out how much to fix (good old VISA's)... if its to much I'll just chuck her on trademe.

I'll let you know if it was the coil.

Thanks for the help.