Rebuilt a 2003 kx125, started up and then died. Suggestions?

yzaddict106
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yzaddict106
Edited Date/Time 10/8/2015 8:05pm
I did my first top end yesterday. I bought the bike of craigslist a few weeks ago, tore it down, and sent the cylinder and new piston off to Millennium Technologies. I got all my parts back and put everything back together. At first I was having major carb issues (as i did a carb clean as well) and after taking it apart and reassembling it 6 times, I found that the float needle sent in the Moose carb kit was half an inch shorter than the old one and was not creating a proper seal. I put the old float back in and everything was good to go there.

So I started the bike up. It started 3rd kick with choke. It slowly revved up, I killed the choke, which dropped the revs and i gave it a blip of the throttle and it died. Now it wont start.

I'm thinking its carb issues again. I may have got some gunk in there while taking it apart so many times or otherwise there may have been some trash left in the bottom of the tank.

Here is my tentative course of action I'm gonna go to the gas station, get all new gas and fresh premix. I'll pull the carb out, clean it again with carb clean and a wire brush to make sure all my jets are clear. Then I'll pull the plug, cap still on, and set it next to the frame and kick it over to verify spark.

Any other ideas or suggestions on potential causes or fixes?
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mxtech1
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mxtech1 10/7/2015 8:00am
10/7/2015 8:00am
New spark plug
Make sure the air intake is clean and clear

Probably in the carb.
Paw Paw 271
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Paw Paw 271 10/7/2015 8:16am
10/7/2015 8:16am
Also check carb vent lines.

Paw Paw
dbrunski125 10/7/2015 11:07am
10/7/2015 11:07am
If none of the above works. Inspect wiring connections. If that doesn't work replace the stator that's doesn't work replace cdi. Process of elimination
project racer 10/7/2015 11:25am
10/7/2015 11:25am
Does it still have compression ? You got the circlips in properly, I hope.

The Shop

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yzaddict106
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yzaddict106 10/7/2015 12:13pm
10/7/2015 12:13pm
project racer wrote:
Does it still have compression ? You got the circlips in properly, I hope.
God I hope so. Both clips went into their groves nicely, both openings facing down.
Barrettp
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Barrettp 10/7/2015 12:57pm
10/7/2015 12:57pm
Sounds like an air leak to me, check the gasket to the reed block and all the hose clamps
yzaddict106
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yzaddict106 10/8/2015 8:42am
10/8/2015 8:42am
I took the carb apart last night. The bowl was full of nastiness. Pilot jet was clear, main jet was completely clogged up. I cleaned it all up and put fresh gas in and it still doesn't start. I pulled the plug and it has a nice, white spark. Not sure what the deal is but I have a feeling it is a fuel/air/carb issue.

I'm going to ponder on it today and tomorrow and then work on it this weekend. Worse case scenario I guess I go back to square one and pull the cylinder.

Any ideas, let me know.
xnationalwrench 10/8/2015 3:21pm
10/8/2015 3:21pm
Not to question you but it sounds like you need to check the carb again. Usually the main jet doesn't get clogged up because of a large orifice, but the pilot jet has a very tiny passage thru the center of the jet and then side passages also. Old school to see if it is the carb is take a thimble full of fuel and pour it in the spark plug hole then reinstall the spark plug and it should at least pop or try to start, if it does you need to rebuild the carb.
yzaddict106
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yzaddict106 10/8/2015 3:59pm
10/8/2015 3:59pm Edited Date/Time 10/8/2015 3:59pm
xnationalwrench wrote:
Not to question you but it sounds like you need to check the carb again. Usually the main jet doesn't get clogged up because of a...
Not to question you but it sounds like you need to check the carb again. Usually the main jet doesn't get clogged up because of a large orifice, but the pilot jet has a very tiny passage thru the center of the jet and then side passages also. Old school to see if it is the carb is take a thimble full of fuel and pour it in the spark plug hole then reinstall the spark plug and it should at least pop or try to start, if it does you need to rebuild the carb.
I know, that's why it's funny. I pulled the pilot jet first, looked through it, blew through it, and then looked again. It always had a pinhole that I could see through. I pulled the main and it looked like a pilot jet opening until I blew through it and it opened way up.

I went back in today and noticed radiator fluid around the cylinder head. I was having problems getting the outer O-ring to set properly and it looks like it caused a gap. I pulled the head off, there was a bit of residue on the head and piston but nothing major. I wiped it all down and went to my local shop who happened to have that outer O-ring in stock. I installed the new one and still nothing.

So i broke out the ol' starter fluid and sprayed it through the air filter. What do you know, started up 2nd kick, so I know i have a carb issue. Also, once it started, the damn thing revved to the moon. There isn't a chain on it at the moment, so I couldnt kick it in gear, panic mode set in and I pulled the fuel line until it ran out of gas. It wasn't until 5 minutes later that I thought of the kill switch!! Man, I've been off a bike too long.

Now I need to figure out A) why it wont start and B ) what the proper settings are so that when it does turn over, it doesn't run straight to the rev limiter.
Paw Paw 271
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Paw Paw 271 10/8/2015 4:09pm
10/8/2015 4:09pm
It's going to rev out of control if it's running lean due to plugged pilot or an air leak. The pilot jet can look clear when in fact it is plugged. Stick a wire through it to be sure it is open or replace it with a new one. You may have crud in the pilot jet carb passages.

Paw Paw
yzaddict106
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yzaddict106 10/8/2015 4:19pm
10/8/2015 4:19pm
Paw Paw 271 wrote:
It's going to rev out of control if it's running lean due to plugged pilot or an air leak. The pilot jet can look clear when...
It's going to rev out of control if it's running lean due to plugged pilot or an air leak. The pilot jet can look clear when in fact it is plugged. Stick a wire through it to be sure it is open or replace it with a new one. You may have crud in the pilot jet carb passages.

Paw Paw
Ok, I'm gonna pull the carb completely apart this weekend and re-clean everything. I'm also going to check to make sure all the jets are correct. With the sour luck I had with the float needle, who knows what is going on in there.
mxtech1
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mxtech1 10/8/2015 8:05pm
10/8/2015 8:05pm
I suggest you might want to go by a new pilot jet since you have a dealership nearby. You should check your air mixture screw. Turn it all the way in and then back it out 2.25 turns. This will get it close. This might help the lean issues.

Do you have slack in your throttle play? Make sure the slide is fully seated when resting.

How does the plating look on the slide and the inside of the carb? I have seen worn slides and carb bodies mimic the situation you are experiencing.

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