99 yz 125 no spark

Hello, I am new to this forum and would like to try to figure out what is wrong with my (semi) newly acquired bike. I bought the bike about 2 months ago and up to now it has run perfect, about two weeks ago though it started acting up. I had just gotten home from a weeks vacation and wanted to go riding but the bike wouldn't start, I thought this was very odd as i had just ridden it the week prior to when I had been gone. I got a new plug for it figuring that it was just flooded, stuck it in and still wouldn't go. That is when i decided to check for spark, and sure enough there wasn't any. I have already checked the grounds and cleaned out the cap connection, as well as ruling out a bad kill switch. Now I am quite confused as to what would be causing this? Is there a way to test the coil? I am pretty handy so I would like to try to fix this myself if i can! Any help would be greatly appreciated!!

First pull the cap off the coil and cut the wire back a half inch, screw the plug back on the wire and give it a go. If still no spark get yourself a manual and multimeter. Check resistance on the coil and stator. If those check out fine replace CDI.

First pull the cap off the coil and cut the wire back a half inch, screw the plug back on the wire and give it a go. If still no spark get yourself a manual and multimeter. Check resistance on the coil and stator. If those check out fine replace CDI.

Will do! Thanks!

So I finally got out to the garage again today and cut the cap back. I am not sure if I tested the coil with the right procedure though, I took put one point in the cap and one on the coil where the wire connects, I didn't get a reading though? I just find it weird that the bike just suddenly won't start?

  1. service manual use it religiously

  1. service manual use it religiously

I was able to find the reading numbers by doing a Google search, I was hoping someone knew the procedure for testing the coil/stator.

I'll trade mi bike for your yz

So I finally got out to the garage again today and cut the cap back. I am not sure if I tested the coil with the right procedure though, I took put one point in the cap and one on the coil where the wire connects, I didn't get a reading though? I just find it weird that the bike just suddenly won't start?

Not sure what you mean when you say "I didn't get a reading" ? Are you using a ohm meter ? Do you have the ohm meter set to the correct scale ? (should be "1", but some digital meters are self sensing) Might be a good idea to take the coil to your local Yammi dealer and the service dept can check it for you.

Not sure what you mean when you say "I didn't get a reading" ? Are you using a ohm meter ? Do you have the ohm meter set to the correct scale ? (should be "1", but some digital meters are self sensing) Might be a good idea to take the coil to your local Yammi dealer and the service dept can check it for you.

Yes I have the right meter and it was set to 1, maybe that is what I will wind up doing although I would like to rule out the stator too if I can.

replace the spark plug cap with an NGK. It's worth the $8.00 just to rule it out. Some YZ's it that era had fussy caps.

replace the spark plug cap with an NGK. It's worth the $8.00 just to rule it out. Some YZ's it that era had fussy caps.

Would I have to order that online or could I get it from a parts store?

So I got my coil trested at my local dealer today and it is not the problem, I also picked up a cap on the way home. Put it back together and still no spark! Stator?

If you have disconnected the kill switch and ruled out wiring then you're only left with Stator and CDI. I've never heard of anybody needing a CDI on a YZ. I have burned out a couple stators over the years on other bikes. If you did need a CDI that might be available from dirtbike junkyard that is always parting stuff on Ebay.

If you have disconnected the kill switch and ruled out wiring then you're only left with Stator and CDI. I've never heard of anybody needing a CDI on a YZ. I have burned out a couple stators over the years on other bikes. If you did need a CDI that might be available from dirtbike junkyard that is always parting stuff on Ebay.

Is there any way to test a stator?

Is there any way to test a stator?

Pick up coil res use + test lead on white/red lead and - test lead on white/blue lead for 248-372 ohms (100 ohm scale)

Source coil 1 res use + test lead on black/red lead and - test lead on green/white lead for 720-1080 ohm (100 ohm scale)

Source 2 coil res use + test lead on green/blue lead and - test lead on black lead for 44-66 ohm (10 ohm scale)

Pick up coil res use + test lead on white/red lead and - test lead on white/blue lead for 248-372 ohms (100 ohm scale)

Source coil 1 res use + test lead on black/red lead and - test lead on green/white lead for 720-1080 ohm (100 ohm scale)

Source 2 coil res use + test lead on green/blue lead and - test lead on black lead for 44-66 ohm (10 ohm scale)

Thanks! That is exactly what I was looking for!

So I found out my stator was bad, I purchased a brand new one off of EBay for a great price and got the bike running. I also found out from my dealer that it is actually a 98 instead of a 99. Now I have a new problem, the bike idles slower than before and it seems to run different, more "pops" and crackles in the exhaust note. I took it out for a test ride and right away it just started bogging after I got to 1/2-3/4 throttle! Only other thing I did was clean the air filter and re-install...any ideas?

Rebuild the carb and clean out all passages, then remove the upper power-valve cover and spray it out with brake cleaner or WD40 if goo is holding it closed.

Any tips with timing? I did read the "250 timing thread" and got some good tips but the timing marks looked different than on my 125. Any help would be greatly appreciated!

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