My YZ 125 is EATING Spark Plugs!!

Less than 20...

Less than 20...

less then 20 hours in 2 years? :thumbsup:

Haha...yeah, I know. It was my friends 2nd bike and it was only ridden on a must need basis....I road it more than they did. So, it didn't get alot of use. One of the reasons why they gave it to me.

That would certainly be in order...but it's got a new bottom end that's less than 2 years old.

the crank that caused me so much problem was only 3 months old. It was a brand new yammy crank and it had a bearing failure off the shelf. Two years on a 125 is a long time. Sure they will last a long time but there is no way of telling how long before they decide to just say no. Most of the ones we pull out are ok and could go a long time more but it's more of a safty thing for me. It's not that expensive to put one in if you can do it yourself but I understand if you have to get a shop to do it.

The chances you have the same problem as I did is not likely but it is highly likely that you have a leaking crank seal at 2 years or even aleak between the cases at some point. Something is causing your detonation problem and you need to find it because it is expensive to keep doing top ends.

you need to find it because it is expensive to keep doing top ends.

Never a more truth to a sentence than that. Thanks Olddude! And yeah, I've learned how to do the top...but I've only been in one bottom end (that sounds bad:devil: ) and don't really know my way around past the crank. I should know more on Saturday. I'm having it pressure tested then. I'll post back with the results.

If you want to make your own leak down tester you can find out how here

http://www.thumpertalk.com/forum/showthread.php?t=506699

I consider a leak down tester to be a neccesity if your going to be doing your own maintenance.

I leak test mine after every top end rebuild and anytime unexpained jetting issues may arise.

AV8R does the pressure tester work well on the newer style YZ250 motors? The reason I ask is because the powervalve is vented to the atmosphere. Would I need to plug that hose as well?

Yes plug the powervalve vent. I use a drill bit that fits tight and stick the smooth part of the shaft into the hose.

I you are leaking air then spray everything, including the tester to see if it has leaks, with a soapy water (dish soap works well as it bubble easily) mix and lots of bubbles will apear where ever the leak is.

It air is escaping from the crankcase vent then the clutch side crank seal is leaking. On the other side you will need to remove the flywheel and stator to spray the crank seal.

If you want to make your own leak down tester you can find out how here

http://www.thumpertalk.com/forum/showthread.php?t=506699

I consider a leak down tester to be a neccesity if your going to be doing your own maintenance.

I leak test mine after every top end rebuild and anytime unexpained jetting issues may arise.

That is pretty neat.:thumbsup: I may have to just test it myself...thanks!

Quick update on this...got it tested this weekend. No leaks. I took the head and barrel back off and am sending those over to him along with the piston to have a look. Hopefully will know more in a couple of days. He said it could be a bad CDI..but he hasn't seen the piston yet....

All right...after seeing the barrel, head and piston, my guy thinks I'm running lean. My first reaction was no way...bike has been jetted the same for at least 4 years and no problems...but being fairly new to MC engines I was also wondering...could clogged jets be causing it run lean and creating this problem?

YES!!!!

YES!!!!

Hmm...are SURE about that? :moon: Thanks snoop...I'm gonna take it apart tonight and find out.:thumbsup:

Ok..pilot jet was completely clogged and the main jet had just a little residue in it. Guess that was the problem. Gonna clean'em up tonight, then drain and rinse the tank. And go from there. Thanks all!!

run a BR9EG

carburetors love to get dirty when you least expect it. It's good that you found the crap and removed it. Combine a clean carb with good pressure test results, good reeds and a good top end and you should be all set :thumbsup:

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now