91 kx 250 ignition problems

[Bigdogdaddy69]

on my buddies 91 kx 250 he was riding last summer and he parked the bike after riding all day, he parked it and later went to ride it, the bike wouldn't start. He bought new cdi box well used off ebay but is in working order, same as the coil. He tested the stator and the coils were bad so he replaced them and still nothing. Now hes about to buy that black box that sits right next to the fly wheel. Anyone know if those can be bought separately? also any feed back on my problem would be nice..

 

[Redrodent]

Fairly certain the pick up you speak of has a set ohm value. Either in range or its bad.

Have you checked all the simple items that will make you kick your self when you overlook them? Ground, wire continuity, kill switch, coil cap connection, different plugs, etc?

If you need some resistance values, I can check my 91 for you

 

[Bigdogdaddy69]

yea i checked all the simple stuff first. if you have all those resistance values that would be handy.

 

[Redrodent]

Let me check the pick up resistance. Be right back.....

White/green stripe to white/red stripe (pick up) 207 ohms
Black/red stripe to red (stator) 433 ohms

Anything else?

 

[Bigdogdaddy69]

his pick up read 190. he bought new coils on stator so those must be good. any readings for coil and cdi?

 

[robbieisurfriend]

Ive got a very similar problem with my bike. I though it was the carb, then the stator, and now the cdi box. Since I bought it I would occasionally have it backfire when trying to start it and when it backfired you knew it wasn't going to start for awhile. It is a timing problem. I am 100% sure it is my cdi because when it does that you can push start it really fast and it will run for a second or two before it drops below a certain rpm point. My theory is that the timing curve gets stuck at a high rpm and it will not run without getting it to that rpm. I got a wild hair and went out to start it today and the first few kicks I could hear it not firing at all. Next two it was trying to backfire but still not right. After a few more kicks it started and ran like new. It has to be the cdi, ordered a new one because I don't want to get stranded somewhere. You might have the exact thing going on. I would try to have a couple of buddies push start you really fast to see if it runs at high rpms. If you think thats what it is then check fleabay, I got one off there for $50. Beats $130 anyday, expecially when you cannot return them and you aren't 100% percent sure it is the problem. Good luck, hope you have better luck than I did.

 

[Redrodent]

Yes, the cdi can't be tested with conventional methods. You need to swap with a known good unit.
For the coil, primary black w/white stripe to ground 1 ohm.
Sparkplug lead to ground 12-20k ohms. You swap this with about any other dirt bike coil for testing.

 

[Bigdogdaddy69]

robbie did your bike have spark if you kicked it over? his bike dont have any spark when you kick it. He also bought a cdi box on ebay he did not get it tested. The coil checks out i believe.

 

[robbieisurfriend]

Yea, I had spark but it was weak. I also thought by black box he meant cdi box. My bad, but still might help somebody one day.

 

[helio lucas]

the cdi ignition timing curve can be tested with a stroboscopic timing light, if you can start your bike... the fastest way to test if it´s stuck on full retard is to advance it... but carefull is needed to do this, do not load the engine for much time, just enough to know if it´s the cdi, or may damage the engine...