WR250f/YZ250f owners around London help!

Hi everyone, first post on here but I've been scouring the topics for a while with plenty of good chit chat.

Anyway long story short...I've stripped my wr250f and completely rebuilt it with new bearings etc no engine work. Gone to start it but I have no spark. Done all the electrical checks using a multimeter following step by step of the owners manual.

The primary coil resistance is meant to be between 0.08-0.10. mine is 0.08 then after a couple of seconds goes down to 0.00. So this could be suspect but not completely sure.

The secondary of the ignition coil is meant to be between 4.6-6.8. Mine is 5.5 so that's average so that's fine.

The only other possible cause is the CDI unit but their isn't any instructions to test its insides.

So before I give Yamaha £100 for a ignition coil or £300 for a CDI, I was hoping someone not to far from me could let me come and attach my ignition coil or possibly the CDI so I can see which one is acting up.

I've found out that the ignition coil fits wr250f's and yz250f's from 2004 - 2009 then just WR's up from 2010 - 2014.

The CDI unit fits only WR's from 2010 - 2014.

If anyone is nice enough to help some poor bugger in need haha I promise il sort you out some beer money for you're troubles I wouldn't be no more than 5mins honestly :)

Kind regards,


Electrical tests like this are hit or miss aa regards values as the quality of your meter affects the readings

Open circuits indicate failed coils

0 ohm continuity indicate short circuit

If you a resistance value when you should then consider it a pass Dont get hung up on values from your meter

Close the plug gap down and see if it generates a spark. This is a good test for a failing coil

Hi Graham thanks for the info I even used a sparks expensive multimeter to test it and had the same results...good tip for the spark plug gap il try that in a bit, thanks

As above, if your primary coil is showing zero ohms, you've got a short.  You should be able to get one from a scrap dealer or ebay.  Very unlikely to be CDI.

As above, if your primary coil is showing zero ohms, you've got a short. You should be able to get one from a scrap dealer or ebay. Very unlikely to be CDI.

Well yesterday I brought the spark plug gap even closer like Graham said and suddenly I had a spark!....put the new spark plug in the coil and I had the spark back with good solid purple/blue ?!?! How strange lol although this is good news it seems their is quite possibly a wire earthing out maybe to the frame or maybe I just didn't push the connectors all in hard enough...il see how it goes. Btw how do I shut this topic down on the iPhone doesn't seem to be any tab to let me

Cool.  If there is still a problem with the coil, you might find that once the engine is under load, it starts mis-firing.

Thanks for yours and Graham's help too guys cheers.

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