Yz125 kinda runs but not really/no power/ hard to start PLEASE HELP !!

wigglez256
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Location
Hartselle, AL, USA
I have a 2000 yz125 I could use some help with! Now I replaced the top end a few weeks ago. Rode it a little bit here and there and didn't have a problem. A couple days ago I go to go for a ride and try to kick it and nothing. I pulled my plug and it was a little blackish but it looked like it had been dipped in fuel. I pulled the carb off and cleaned it and all the Jets / fuel&air screw. Probably repeated this about 6 or 7 times and still nothing. Noticed my gas was leaking from my bowl so I very tediously adjusted the float height and now I'm not leaking out of my bowl. STILL COULDNT GET IT STARTED. after going through 5 different plugs ranging from 7s to 9s I finally got frustrated and held it WOT and kicked the shit out of it and it finally fired up. It idles decent but underload the thing is a complete turd and will hardly go anywhere. I just cleaned out my powervalve assembly while doing the top end a couple weeks ago so I was pretty confident that wouldn't be the problem. I've heard of the cdi causing some of these symptoms or maybe the stator but like I said it will idle but as soon as you blip the throttle or ride a few feet it wants to bog really bad and die. Could it be the powervalve not working properly or could this be a carb issue even thought I went through it a dozen times cleaning it and making sure nothing was clogged? Any advice would probably help at this point!!

Mixture is 32:1
Plug of choice br8eg
Stock jets
Stock pipe
Vforce reeds (shows no light thru)
Namura 53.94 with maybe 10 hrs on it
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Paw Paw 271
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Benton, LA, USA
2/9/2020 4:03pm
If the bike flooded with fuel from the float setting being too high, then your crank cavity is full of non burnt fuel. It will have to be cleaned out before it will run correctly.
You said a few weeks.... How long exactly? Your fuel could have separated and is now bad.

Paw Paw

1
wigglez256
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Hartselle, AL, USA
2/9/2020 4:23pm
I replaced the top end and cleaned/maintnenced the power valve about 3-4 weeks ago it has maybe 8 hours on it of flawless ride time. I ride it daily weather permitting so it doesn't sit with a tank of gas in it too long by any means I put gas in it maybe 2 days ago. It's been running really good so far my plugs have been usually brownish colored.

Yesterday I went to ride with some guys and it wouldn't start it would putter for maybe half a second then die and I couldn't even get it to do that again. I took my carb off cleaned everything out shot cleaner and air down all passages I could find. Put it all back together and then my bowl starts leaking (still won't start). Noticed my filter on my fuel line wasn't pushing fuel down so I cleaned it and got fuel down in the carb. Still no fire. Made sure I got a nice spark from my plug and I have good spark . Pulled out my reeds and I can't see any light thru them . Adjusted my heights by removing my bowl and attaching my fuel line then i could see exactly by pushing up and down on the floats where it releases fuel. Just a way I was shown a long time ago 🤷 it stopped my bowl from leaking and I finally (under WOT and a buncha kicks) got it started. Idled pretty good but had that slight bog when you blip the throttle. Still rode down the street and as soon as I gave it any juice at all it would just go flat. No acceleration no powerband no anything just a flat bog all the way past 1/4 throttle or so. I've had a faulty powervalve before and it would still go up in rpms under load but it wouldn't hit the pipe and would be super flat. This is like it just won't go when you give it throttle but it will put put around seemingly fine 🤔

Just went to kick it out of curiosity and it will only run with the choke on
Paw Paw 271
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Location
Benton, LA, USA
2/9/2020 7:29pm
If it will only run with the choke on, you have an air leak or your pilot jet is clogged up. Unless you pulled each jet and cleaned them properly, you have not really cleaned the carb.

Paw Paw
wigglez256
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Location
Hartselle, AL, USA
2/9/2020 9:25pm
I cleaned each one by blasting carb cleaner down them then shot them with air. I repeated this probably 6 times over the past 2 days

The Shop

FWYT
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San Diego, CA, USA
2/9/2020 11:55pm
Well, one thing you can check super easy is the power valves. Pop that cover off. Those pins that are in the valves are notorious for falling out rendering the power valves no-worky. At least take a look. If not that, follow Paw Paw's advice.
1
Paw Paw 271
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2/10/2020 6:51am Edited Date/Time 2/10/2020 6:51am
wigglez256 wrote:
I cleaned each one by blasting carb cleaner down them then shot them with air. I repeated this probably 6 times over the past 2 days
Again...Unless you took each jet out of the carb and cleaned each one by hand you have not cleaned the carb!!!!!
Carb cleaner spray and air just will not cut it!

Paw Paw
wigglez256
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Location
Hartselle, AL, USA
2/11/2020 10:17am
Yes by hand multiple times every jet my idle screw air fuel screw etc. It's a mikuni carb very simple to clean and remove jets
wigglez256
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Location
Hartselle, AL, USA
2/16/2020 7:06pm
Update:

Finally got around to taking the jug off and tore into the powervalve. I think I located the culprit! The pins on the exhaust valves had fallen out and we're just chilling. I cleaned everything out and went to put the pins in and noticed one side is easy to slide the pin in where as the other side is really difficult. you really have to push that sucker in there which would make sense. I could see how the other pin fell out as it was easy to push in and out I don't see at all how the other side fell out since it literally takes pliers to pull it out. Any ideas on a simple solution? Some sort of loktite? Or should I try to source some more pins? Thanks !
1
FWYT
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2/17/2020 12:42am
wigglez256 wrote:
Update: Finally got around to taking the jug off and tore into the powervalve. I think I located the culprit! The pins on the exhaust valves...
Update:

Finally got around to taking the jug off and tore into the powervalve. I think I located the culprit! The pins on the exhaust valves had fallen out and we're just chilling. I cleaned everything out and went to put the pins in and noticed one side is easy to slide the pin in where as the other side is really difficult. you really have to push that sucker in there which would make sense. I could see how the other pin fell out as it was easy to push in and out I don't see at all how the other side fell out since it literally takes pliers to pull it out. Any ideas on a simple solution? Some sort of loktite? Or should I try to source some more pins? Thanks !
Ha! I guessed right! Laughing

Anyway, yeah, they are kind of notorious for doing that. Mine did the same thing. (Well, actually my nephew's bike that I am currently refreshing for him like a good uncle.) What I did was take the pins to the local Ace hardware and matched them up with some roll pins. Found a size that was just a hair tight and could be pressed in with a vice. Presto, cheap-o, fix-o.
1
wigglez256
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Location
Hartselle, AL, USA
2/25/2020 11:16am
Update #2 ended up welding the pins in since I had a welder handy powervalve now works like a charm! Now I have another problem as the carb is leaking but it's not leaking out of the bowl overflow it's leaking out of the little vent hose where the reeds go. I don't want to flood my case even though I probably already have. Is this a float height problem? Should I just say screw it and wait a few days for the carb kit to come in? I tried adjusting the Tang a little bit but i think I went the wrong way? Bent it slightly up. I'm having trouble finding good info on adjusting the float height for a mikuni

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