KX 125 won't start have tried everything

Ok I need some help I have a 99 KX 125. My buddy has a KX 125 and I was riding it and it died on me. It hasn't started since. we have gone through the manuel and tried the suggestions in the troubleshooting guide. The carb is getting fuel but it won't leave the carb. The bikes compression is good, we have cheked the jetting, replaced the sparkplug, tested the Fuel Cut valve, we are starting to think it maybe the capacitor, not sure what else it could be any suggestions? Has had a lot of motor work recently prior to this ride.

Do you have spark ? Are any jets blocked ?

Air + Fuel + Spark + Compression = ignition

IF the carb is getting Fuel but it is not getting into the cylinder, I would check the AIR. bad reeds may cause a loss of velocity.

It could also be bad compression but you state that the fuel is not leaving the carb.

rip apart the whole intake and clean, inspect and reassemble.

easy test for the ignition is to get a buddy to hold the sparkplu against the engine block and then give the bike a gentle kick over.

DO NOT hold the spark plug itself, I realized this after I picked myself up 20 feet away from a bike when I was 13 :lol:

DO NOT hold the spark plug itself, I realized this after I picked myself up 20 feet away from a bike when I was 13 :lol:

SHOCKED into reality @ 13.:lol::busted::worthy::banghead:

J/K man.That is a great bit of advise however and one that I should have been aware of @47(last year) as I was messing around w/my lawn tractor-I turned the key,spinning the starter as i was arcing(misspelled?) the plug holding it in my bare hand.DUH.

it was a moment of clarity that had escaped me over the years I assume-

The pilot circuit is plugged. How much compression did you have on the test?

we did the spark test while on the trail and it sparks. (luckily we knew not to hold the spark plug so we didn't set shocked)

The jetts are brand new could they still be bad?

I don't know about the compression test i'll ask my buddy.

You did turn on the fuel right???

Yeah the fuel is on

we did the spark test while on the trail and it sparks. (luckily we knew not to hold the spark plug so we didn't set shocked)

The jetts are brand new could they still be bad?

I don't know about the compression test i'll ask my buddy.

someone dumped in your gas tank when you werent looking im tellin you man thats always the problem
or theres a poop in the carb blocking everything:ride: :foul::banana::bonk::p:moon::lol: :lol: :p:banana::foul::lol::moon::lol::mad::ride:
Yeah the fuel is on

Pretty much worthless advice here.

I would check the spark quality. Fat blue spark. What was the compression reading?

Check the reeds, they may be split and/or missing pieces.

Another thing to look at is crank seals. If they leak, it will run lean and be hard to start.

Have you tried push starting it?

DO NOT hold the spark plug itself, I realized this after I picked myself up 20 feet away from a bike when I was 13 :p

I just learned this last night, its not cool. I was holding a metal table with my other hand also.

we haven't tried to push start it yet. I never thought about giving that a try. We won't be able to get to it til wed but will update when we give the push start a try.

Just a quick thought.

when you say fuel is getting to the carb, do you mean that the fuel runs through the fuel line, or is the float bowl filling with fuel?

you could have a situation where the float bowl is not filing.

have you torn the intake apart and cleaned it.

and Yes I mean from a clean air filter to a carb disassemble and cleaning, verify the carb is set to stock, the jets are in properly and not clogged and that you are at base settings for the area (or at least factory settings).

as said, the pilot cicuit. otherwise, you said it has compression. How much though? does it feel like it has compression or did you actually test it. At 90psi, it'll feel like good compression but 95% chance it won't start. Do a legitimate compression check then let us know and we might be able to narrow it down a little better. Also check for any gaps in the reeds against the block.

Fuel is getting to the bowl.

if its the compression what would be causing that? I don't know much about 2 strokes. My friend told me though that he had it in the shop a month prior to our ride for a leak in the the water pump. They did a compression test while it was in the shop and it was fine and they also replaced the jetts then. Is it possible that the jetts can go bad at one ride?

what was the compression ? it should be about 160-190. 175 is prime.

the compression was at 170.

The compression WAS at 170 but what is it now? You need to test it now and not rely on what it WAS. You can get all the fuel you need with a fat blue spark but with little to no compression it still won't run. Push starting a bike will run with low compression. It needs to be 100PSI + to be able to kick start. If you test it and get a reading above 100psi then the pilot jet is plugged.

it WAS at 170 when we tested it yesterday

You may be getting spark yes, but check your timing and make sure its spot on. it may have came loose.

tear down your carb and verify everything is clear, this only takes 15 minutes or so.

another thing you can do (if you have a spare reed to carb adaptor, dont do this with your only one) tie in a vacuum gauge and kick it over with the throttle shut, if you have vacuum you will know you dont have a major air leak.

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

  • Similar Content

    • By luke8500
      Hi all,
      I have a 2004 Kawasaki kx250 that died suddenly on me the other day. all i can get it to do is backfire every once in awhile. Tested the resistance and everything of the magneto and stator with a multi-meter and all is good.  Coil is new oem Kawasaki the reeds are brand new vforce and the top end and carb have been completely rebuilt.  key on crank is intact and all the timing marks are lined up. I hooked a timing light to it and spun the motor over really fast and found that it is sparking way to late.  The service manual says that it is supposed to fire 14 degrees before TDC but it is sparking way after TDC.  Im thinking its a fried CDI box since its the only thing i wasnt able to check.  Any help would be appreciated
    • By luke8500
      Hi all,
      I have a 2004 kx 250 2 stroke and it wont start.  it only backfires.  I was out riding it one day and came up to a stop so the bike was just idling and it started to try and die so i revved it up a few times then let it die and now it wont start back up.  It only pops or backfires when you kick it.  Its getting good spark and i just put a brand new plug and coil in it. I took the reeds apart and they look like they're brand new.  It was running great before so i dont know what happened.  Im thinking it could be a fuel problem even tho the plug is a little wet if you take it out after a bunch of kicking.  Any help would be greatly appreciated 
    • By Zach121
      Alright, found three bikes all located where i live in Texas. I know they're all very different, but if you could tell me what you think each bike is worth, and which one would be the best deal. Thanks.
      Notes: Both 2 strokes have new top ends. I think the front brake lever is broken on the kawasaki.
      KX250 2002 $800-$1000?

      YZ125 2000 $1250

      KTM 400SX 2002 $1200

    • By Ryan Turner
      So I'm at a bit of a cross roads, I currently own a 06 rm250 and I love it. I also have a 02 kx250 which I'm selling with intent to buy a newer two stroke. I can't afford a newer ktm and the older ones aren't that great and kawasaki never impressed me. so I'm stuck between 06 yz250 and 05 cr250. I've heard the yz and rm after 06 are almost the same bike just the Suzuki handles better and the Yamaha has better suspension. So I'm not sure if I wanna buy carbon copy of my bike with slight differences. That's why I'm interested in a cr250 I heard the 02+ models RC valves are shit garbage but was mostly fixed in the 05-07 models. I ride at a track and at some bogs down the road from me. So from people who have owned both, what would you recommend. I know the cr is known for a hard hitting power band which I enjoy since im an aggressive rider. Should i just see which deal comes my way first.
    • By dirtbikesrule
      If you own a 2 stroke dirtbike,please reply once. Im just wondering how many people on this site have them.