RM 250, weak/no spark

[mxman2000]

Hi,

I have been having a problem with my 01 rm250 that it cuts out. today it started and then when going just lost all its revs and died. now i have what appears to be no spark at all. I have touched the plug while kicking and no shock off it but sometimes it looks like there is a very weak spark. i have changed the spark plug and looked to see if there are any shorted cables. Also dissconnected kill switch.

Another thing i tried was checking for continuity from the cdi units plug to all the ends and all the ones i tested seemed fine.

Any ideas anyone?

 

[jsantapau]

if the spark is any color than blue ohm test the coil I am not sure how you tested the cdi since any manual I have seen doesn't have values for a cdi

 

[RM_guy]

The RM manual has all of the values for the CDI but I've never had luck measuring them. Check for breaks in the harness by measuring the continuity when wiggling the wires. I didn't find a break in mine until I did that and actually replaced the stator before I found the break. I have a good stator if you need one.

Here's a picture of the manual for testing the CDI. I hope it comes out clear enough to read.

 

[jsantapau]

wow that is a lot better than anything i have seen! so you test for stored voltage in the diodes? am I reading that manual page correct? I need some schooling here on how this works. I thought diodes where like one way valves and capacitors stored elecricity. Are using voltage from the ohmeter to check the one way effectiveness of the diode? did I just answer myself with that last question?

 

[mxman2000]

The RM manual has all of the values for the CDI but I've never had luck measuring them. Check for breaks in the harness by measuring the continuity when wiggling the wires. I didn't find a break in mine until I did that and actually replaced the stator before I found the break. I have a good stator if you need one.

Here's a picture of the manual for testing the CDI. I hope it comes out clear enough to read.

I have not actually tested the cdi unit but i have the book and tomorrow will take some readings. Things i have done are.

-test continuity from cdi plug to all connectors coming off it.
-change spark plug
-cut about 20mm of the spark plug cable
-wd40 over all the connectors incase of water
-fiddle about with wires incase of a break


If its not a break in one of the wires i think it could possibly be either the stator or the ignition coil. hopefully find out tomorrow.


The fault is definately electrical though, i had the same problem before but taking the tank off and then putting it back on seemed to solve the problem. This made me think it was a short in one of the wires but maybe the coil was dying anyway. Sometimes could be difficult to kick but would always bump. Although now nothing seems to start it :(


can anyone tell me, will any coil from another mx bike work in mine or will this cause problems. Ie could i use a of a ktm/cr/kx/yz? or only a coil of an 01 rm 250?

 

[RM_guy]

jsantapau, I’m mechanical, not electrical so I’m just a lost. I can usually muddle through it but this was beyond me. Luckily I found the break and didn’t have to deal with it ;)

Mxman2000, If removing and replacing the tank corrected the issue in the past then it’s most likely an intermittent break that finally became open. Recheck continuity around the tank area first and really pull on the harness, trying to stretch it, to open up any breaks that may be there. It took me a while to find it and I was ready to take it top the shop to have everything checked out with the proper meters.

Good luck.

 

[mxman2000]

jsantapau, I’m mechanical, not electrical so I’m just a lost. I can usually muddle through it but this was beyond me. Luckily I found the break and didn’t have to deal with it ;)

Mxman2000, If removing and replacing the tank corrected the issue in the past then it’s most likely an intermittent break that finally became open. Recheck continuity around the tank area first and really pull on the harness, trying to stretch it, to open up any breaks that may be there. It took me a while to find it and I was ready to take it top the shop to have everything checked out with the proper meters.

Good luck.

I had the whole lot off today, tested the stator and the coil and the cdi, all gave me the correct readings. So just when i was about to give up i completely peeled off all the sheathes off every cable and found the break. Although it beeped out with a continuity check it was just enougbh to not start. Later this week i will get it all put back together properly. :)

so problem is now

FIXED

Thx for everyones help.

 

[RM_guy]

:cool: