125-200cc 8 miles per plug, this is getting old...

2009 CR125

Was running fine, now it has started fouling plugs on the regular. Nothing has changed jetting wise so I am not looking to start there. It did the same thing last year, fouled 4 plugs in 40 miles. To fix it then I cleaned and dielectric greased all electrical plugs and sanded the coil mount points.

After that the plug lasted 52 engine hours, no jetting changes, nada, nothing has changed then bam started fouling plugs again. The only other symptom that leads up to the plug fouling is hard starting when the engine is cold. It will take 5-6 kicks, then fire, run slowly for a few seconds and die. Repeat 4-5 times at one kick each then it will take off go to normal high idle with the choke on and be fine for the rest of the day.

This time I did everything I did last time, and more. Now it starts fine cold, first kick today. But still fouling plugs. It runs perfect, doesn't load up, doesn't do anything odd then just blahhhhhhhhh dead.

I have done this stuff so far...

Cleaned all connections.
Replaced plug, lots, BR9ES BR9EG BR8ES doesn't seem to matter. Weekend camping trip took 5 plugs to get through 65 miles.
Cleaned, sanded, dielectric greased all connections.
Changed plug
Changed spark plug boot.
Changed plug. 5.8 miles
Cleaned, sanded, dielectric greased all connections.
Added extra ground wire from the coil to the engine.
Changed plug. 7.5 miles
Changed complete coil.
Changed plug. 8.5 miles
Changed CDI...

Have not had a chance to ride it yet, maybe tomorrow. I will try to get helmet cam footage...

I have 2 complete spare bikes to test parts off of, next is the wiring harness, then stator/pulse generator. After that? There better not be an after that.

It is really frustrating having a bike that is not reliable enough to take on the trail without buying stock in NGK. The good rides the last few weeks have been on my trusty 400+ hour 2003 WR250f while my 2 sweet Huskys hold down the floor of my garage. My TXC250 lost the lower rod bearing at just under 200 hours... That doesn't bother me nearly as much as my plug fouling 125 that runs great, 8 miles at a time.


Later,

check your right crank seal

Have you checked your jetting?

Sorry Jake, you know way more about these bikes than me, so the only comment I have is a smart-assed one...

What do the reeds look like ?

I think you should stay focused on the electrics. Try swapping out the stator assembly.

I wonder if you have temperature dependent short in your exciter coils. Producing inconsistant spark strength when it gets hot. Just a thought.

Maybe just an incredible run of bad luck with plugs?? ... Maybe try a plug someone else purchased instead of that bad lot of plugs you have encountered ...

Maybe try a WR ignition. I'll swap you

Seriously though, have you tried a fresh batch of gas? What oil are you running and what ratio?

have you checked the compression on the 125, whats it reading?

Check the reeds and crank seals first.

I am going to go through the electronics first, then to the mechanical items, it is not loosing any oil or smoking badly but you may still be correct.

I will re check my jetting just for you Blake...

They are black, carbon fiber petal looking things... Oh, non smart ass answer is, I looked at them 50 hours ago and they looked fine last time this issue came up. I will pull them if the electronics swap comes up empty.

Good to know, I may be bugging you to try that. Here is how they looked last time I pulled them.

You may have something there, the plug has fouled consistently the last few times within a couple hundred yards of a hot startup. Like something is heat soaking. It also seems that the harder I run it the faster they foul.

I put too many words in my original post for you didn't I Kelly... Here let me quote myself...

Spark plugs have been from 4 different sources, friends, family, NAPA, Bike shop...

Chevron super and Klotz R50 32:1 as I have been for over a year, this gas is shared between 4-5 other bikes and they have been fine.

I have not, but I will try to do that tonight. Anyone want to post the propper method? Cold engine, wide open throttle, 5 kicks? It has been so long I can't remember.

Later,

Jake,

Warm engine, Kick until you don't see any further increase, throttle wide open, kill button engaged. It will never create more pressure on your meter than its actual developed compression. Kick it firmly, no wimpy stabs that are all you need to start it normally.

Just clutching at straws here as you say the coil was changed !
The other week I was looking at a 09 that had lost its spark and after dissconecting the kill switch it ran fine and the rider carried on for the day
New kill switch fitted and no spark, so I looked at again at my house and the bike would spark first kick then nothing with the kill connected !
Tested everything and all seemed fine that is till I got a huge shock from the LT side of the coil, somehow the coil was feeding the HT side back through the LT side (blue wire) fitted a new coil and all was fine
Worth looking at perhaps
And looking at the pic of the reeds the upper right side as viewed looks to have slightly chipped so may have gotten worse

Compression is 156lbs or so.

Not the CDI.

Swapping stator now...

Later,

I owned and operated an auto shop for 20+ years and only had one new spark plug that was defective. It visually looked fine but had a bad pattern on the scope and misfired from the second it was installed. This is after thousands of V-8 tune-ups. I'd bet my house that you won't/didn't get 4 plugs in a row that are bad... if China starts making spark plugs all bets are off.

My Dad rode 11.2 miles today to test THE CDI, it was runing fine when he parked it. I started it and the plug fouled in .3 miles.

Now we swapped the stator and did a 4 mile run. Letting it cool now and will ride it again shortly.

Later,