I have a '85 Tri-Z 250 that is killing sparkplugs witout the engine running. If I put a brand new sparkplug (NGK B8ES) in it will spark great for a few kicks, then the spark will get weaker, then weaker, then after about 15 kicks the sparkplug is dead! I can get a new sparkplug and same thing all over again. I installed another voltage regulator and still same thing. Any ideas? The electrical system is about as simple as it gets with a stator, CDI, regulator, ignition coil, kill switch, headlights and that's about it. Or if anyone has some info on the specs for this stuff I have a multimeter.

 

well if it is the spark getting weaker and weaker and not something else then its most likely the ign. coil or stator, i would definitely start off with those and try to get some specs for them and see if they fall within spec.

 

Yeah, it's definately the spark gets weaker. I took the plug out of the engine and hooked the plug back to the coil, then grounded the plug and kicked the engine over by hand, and watched the spark. It's great for 2-3 kicks then it gets weaker then finally the spark goes away. I've never seen this happen before. Anybody know where to get the specs?

 

I ordered another CDI for it, if it's not bad at least I will have a spare. I hate just replacing parts without proving what's bad. Does anybody know what a CDI actually does? I know it stands for "Capacitor Discharge Ignition", but what does that mean? I already replaced one CDI last year, it just died on me while out on the trail one day. I'm wondering if whatever is killing my plugs could be killing my CDI unit as well? Any input is appreciated.

 

what CDI does is the stator slowly loads up the capacitor(between each fire) and every time it needs to spark it unloads the capacitor or dischages the power into the spark plug wire and then into the plug to create spark. i wonder if the capacitor is done for?

 

Cool, where does the ignition coil come into play? I understand electricity but I never have understood how the electronics work on these old 2 strokes. The capacitor could be bad. I hope it's not the stator.

 

seeing your trike makes me wanna get one, not sure what they go for, id be interested in the yamis and the hondas, how bad is it riding on atv trails though? i would think it would be a pain at times.

 

They are cool and get lots of attention out on the trails and the local ride spots, and usually nobody else will be on a bike like yours, but that's about where the coolness stops. The suspension sucks compared to todays quads and they tip over easily if you're not careful on off-camber hills. I just installed a +4" Lonestar axle on mine to help this, as soon as I get that piece running I'm going to try it out. I can't ride nearly as fast as the YFZ's and Raptors on trails, but I'm getting too old for all that anyway!

You can find these for $300 - 3,000. I paid $1400 for mine and have spent about $2,000 getting it where it is today - way too much invested, but it was a fun experience. I like the look of the Yamaha Tri-Z's the best, but the Honda 250R's and 350X (4 stroke) are more popular and more plentiful.

 

hmm, didn't think it had a ignition coil. i was thinking back to my polaris 340 with cdi ignition, and it doesn't have coils. i can't really help you, but i would take a test light to the wires coming from the stator while someone kicks it over and see what you get.

 

over twenty years ago i remember the same thing happend on my 85' tri-z, it ended up being the coil, is was 13 then so bare with me. i remember it eating pluggs, i had small town sponsorship through our yamaha shop and the mechanic told me he replaced the coil... wow long time ago. any way they say to test the cdi with a known good component rule. that always told me they don't know how to test one lol. i wouldn't worry about a book just yet. ck-to make sure stator, coil, etc. have good component grounds, the stator sends a pulse signal to the cdi, you would notice a wire coming out of the stator pulsing your test light dimly but steady. current goes to the (pre-mapped) cdi. each cdi has been designed with a spark curve, and rev. limit for that specific machine, then current goes to the coil were the coil is just one big resistor, or capacitor(gathers and holds an electric charge), generates a healthy spark20 to 60kv exp. then goes through the hi-tension lead to the spark plug to ground.