Yamaha 25 nmo

Service manual give complete details in testing CDI unit

I have 2002 road star midnight. I lost completely spark on all 4 spark plugs. Before bike was running OK but sometimes on low RPM while idling would skip a firing on a at least one cylinder making spufff like sound. I put new spark plugs, and wiggled a little coil wires. Bike with new spurk plugs would not fire up at all. Checked for spark on all 4 spark plugs - no spark., not even an electrical I lost completely spark on all 4 spark plugs. Before bike was running OK but sometimes on low RPM while idling would skip a firing on a at least one cylinder making spufff like sound. I put new spark plugs, and wiggled a little coil wires. Bike with new spark plugs would not fire up at all. Checked for spark on all 4 spark plugs - no spark., not even an electrical charge going to spark plug. Went back to coils. Each coil (there 2 of them) has 2 spark plug wires and 2 ignition timing signal wires connected to them. I realized that these ignition timing wires contacts are corroded to the point they would not conduct a charge from the distributor to coil. CLEAN ALL THE TIMING WIRES Contacts on the coils. I did that and bike fired up right away and started running much better without sputtering or skipping a cylinder firing. SO DISCONNECT ALL THE COIL WIRES AND BRUSH THE CONTACTS WITH A SMALL METAL WIRE BRUSH.

CDI units are generally make and model specific. Some models share a common CDI but very rarely do makes share. So I think I would be right in saying the answer is no.

hi,about the only thing you havent replaced is probably the culprit,it sounds like one of the pickups has failed and gone open circuit,this will tell the cdi unit that the pickup has already fired and not send the voltage pulse through to the coils,hope this helps...cheers

hello, i just purchased a after market cdi from, procom engineering inc. 66 maxwell irvine ca, 92618 usa. tel, 949-748-6338, or www. procomengineering.com, i purchased cdi for 350 warrior,this cdi advances timing, hotter spark, easier to start, i am very pleased with mine, it was 76.00 dollars, this is a aftermarket high performance cdi, beats paying 500.00 from yamaha shop, try it i believe you want be dissapointed, they have warranty with it. check it out, they ship pretty fast too, bubba

Yamaha ignition coils never go bad. It is probably the Stator/ Pulser coil (very common). You can check them with a ohm meter. You'll need the readings from a Yamaha dealership. The CDI box is very seldom bad But there is no checks that can be done on it. If everything else is fine ---than Yamaha says it must be the CDI box.(Rare)