125-200cc 125 Troubleshooting???

OK, so a little background....Went to Canada for the summer with a good running 125 with about 5hrs on a fresh ring(125hours total on bike, 25 on newest piston). Two months in and roughly 30hrs she lost the off idle lug/grunt. I figured it was time for another new ring, so I tore in and found a ton of little gunky black residue(assuming this was from running castor 927, know better now). There was to much to clean by hand so I put the whole cylinder in boiling water under a close eye(maybe this is my problem, but I had no choice, it was my vacation and I was up at the lake), all seemed well the cylinder cleaned right up, slapped it back together did a couple heat cycles and was on my way( big shout out to ScottyR for overnighting some gaskets to me, saved my vacay). Bike ran great, just as before, made it through week no problems. Well I still had a week left in Canada and right before I left after my grandfathers 80th surprise party I decided to hit the lake one more time. The bike fired up, but had no low end again, decided it might be jetting or worse so I just took my Dad's xr250 out.

Fast Forward a month and a half and back in Florida. Finally have a bit of a break from school and work to hit the trails, new ones at that, and decide to chance it with the 125, it's that or the old IT 200(my 250 grenaded on me in canada and have yet to fix it). So I get to my buddys fire her up, very little low end again, played with the air screw a bit, but not much head way. Figure I'll just have to ride it like a jap 125,lol. The bike runs fine from the midrange on up and I'm really feeling right back at home in the sand and battling it out with my buds freshly rebuilt 01 Honda CR 250. Here's where it gets funky, a handful of times when I'm coming off full throttle back down to idle the bike bogs real bad; sometimes causing me to stall out. When starting the bike back up after these scenarios, it will only start with the choke, sometimes I actually had to ride on the choke a few feet to get rolling. What's weird is when I killed the bike on purpose with the switch I did not need the choke, just the old 1/4 throttle and kick. So we end up riding some more and it happens one last time, except the bike will barely fire and will not run, changed plugs, checked the stator(went through some water), but no luck, ended up pushing the bike out in the sand, I lost like 5lbs(at least something good came of this, lol)

So I went over the bike on Sunday, checked the reeds(fine), cleaned the carb/went one step richer on the pilot to 45(PWK), changed the oil/and air filter, checked the fuel line for obstruction(fine), and tried to start it, but nothing won't start at all, the headlight starts to come on but the bike does not fire, bump start nothing. So I just did three compression tests, all came out in the 150-155 range, low but the bike should still run.

Wondering what you all think, is it time for a full rebuild crank and EG 144 or? Just came to me Woodruff key? I was hoping to sell/trade her in for an 09 WR125, but doesn't look like that's gonna happen now,

Maybe I jinxed myself with part out thread.

155 is way low. im guessing thats with the engine cold. the only way to get a true reading is with the enig warmed up to running temps.

mine was 120 before i ringed it. it was a turd too. how old is your piston? what year is your bike?

have you checked and cleande all of you carb vent hoses? and are you running the right plug?

ps. i love my 144 from Mr. Gorr

Check for spark. The headlight bulb may still light up when you kick even if there's no spark.

I had bad low-end performance and hard starting when I was running that KTM stator. That is, until it completely quit and I had to get towed out of the woods. It would still light up the headlight when kicking and trying to bump start it, but there was simply no spark.

hmm.....only wanting to run with choke...


crk seal....try some carb cleaner spray or alcohol spray under the stator cover...rpm increase suggests it leaking.....

and also the vent hose..to check the clutch side


strange.....

Bike won't start at all, not even giving any signs of firing. It is getting spark, as said before the reeds look fine, compression is low, but it was running pretty good in the midrange and up top. Can't do the crank seal test cause bike won't start, I replaced the RHS crank seal 60 hrs ago. If the woodruff key had sheared are there any telltale signs without taking apart the flywheel, the ignition nut isn't loose and the stator spins when I kick it over. Is it just me or have I not had my fair share of problems with this bike?

A sheared keyway I had once.....but your right the nut backs off as a result....

Well, go back to basics, I guess. If the bike has fuel, air, spark and compression, it should start. Check for fuel flow from the tank, fuel in the carb, quality/contamination of the fuel, check for dislodged/clogged jets, make sure the needle and slide move properly. Look for obstruction in the air box and intake. If you're getting spark, perhaps the timing is off. Pull the flywheel and make sure the stator timing marks align. If all these things check out, then I suppose you have to suspect the compression.

Definitely check that all the carb parts are where they're supposed to be. A buddy of mine couldn't get his bike to run off-idle. As soon as he cracked the throttle, it would die. Turns out the clip came off his needle, so the needle wasn't moving upwards with the slide when he cracked the throttle. Took us a while to figure that one out.

It ended up being the carb, I'm guessing the pwk just needs a thorough cleaning(preferably by machine), and probably a rebuild kit. I just put the TMX back on and she fired right up(oh the irony), needs a little jetting, but at least I have one modern bike running now. I still think I'm going to sell my IT and the 125 and try to get on an 09, that one in the classifieds is tormenting me.