RM125 Carb keeps running fuel out overflow

Boxvan446
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Boxvan446
Edited Date/Time 1/24/2012 11:49am
I have a 2000 Suzuki RM125 that I am in the process of re-doing. Anyway, I got it all back together, rode it, and went great for a little bit and then started to bog like it was going to foul a plug. If I really hammered the throtle I could get it out of the bog, but everytime I looked down or put it on the stand (and shut it off), fuel was running out the overflow hose. So I took it apart and looked at the float and float valve, because that is where everyone says the problem is. I could not see anything wrong with either, but I ordered brand new OEM replacements and installed them. Started the bike up and within 3-4 mins of riding it is doing the same thing. I have the carb apart right now and have just adjusted the float height to the stock recommendation of 16mm. It was at about 15mm before I took I adjusted it. Is there anything I am missing or should be looking at? Any help would be appreciated.
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OldTiddler
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OldTiddler 4/24/2011 7:43pm
4/24/2011 7:43pm
It's normal for some fuel to come out when putting it on a stand, since you're tipping the bike a bit and what's in the bowl will spill over a little, but not while it's sitting still/upright.

All the fuel comes through and is shut off by that float valve, so overflow means it's not stopping the flow for some reason. The valve shouldn't be worn and there should not be any debris that would cause it to not seat well and make a "closed" seal. Also, setting the float height can be tricky, if problems persist even after double checking this you might try even lower just to see if this affects it at all.

What does the plug look like after you run it?
Boxvan446
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Boxvan446 4/25/2011 7:57am
4/25/2011 7:57am
Everything looks good on the plug. It dumps fuel out after being upright on the stand for awhile. Everrything is clean, I've inspected it numerous times. I was leaning toward a float level issue myself. But just wanted to check and see if there was anything else I was missing. Thanks for the reply.
Boxvan446
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Boxvan446 4/25/2011 10:30am
4/25/2011 10:30am
At 16mm right now (stock recommendation). Going to try it later today when work is done.

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lumpy790
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lumpy790 4/25/2011 12:07pm
4/25/2011 12:07pm
shake the float to make sure there isn't a leak.
xnationalwrench 4/25/2011 12:29pm
4/25/2011 12:29pm
Also check the needle in the needle & seat assembly for wear on the tip if it doesn't seal properly it doesn't matter what the level is.
Boxvan446
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Boxvan446 4/26/2011 5:33am
4/26/2011 5:33am
I put it all back together with the new float, float valve and adjusted the floats to the correct height and it still pours gas out the overflow. One thing I did notice is that after the bike is off it keeps running fuel out unless I shut off the gas. I turn the gas back on and it keeps running out. So that leads me to believe that the float valve is not sealing properly. I've checked to make sure that it is full seated when the carb is off and I have it apart. I'm starting to wonder if I'm missing something in the carb (in particular, around where the float valve seats) altogether. I'll take a look at the needle/seat assembly closer tonight. I didn't want to look at it much last night after it failed for the 4th time now.
motofab36
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motofab36 4/26/2011 6:23am
4/26/2011 6:23am
I'm pretty sure that carb has a drain screw on the bowl, take it out and clean the tip of the screw and the area down in the bowl where the screw seats. If the drain screw is not seated and sealing properly it will let gas run out.

Another quick test while you have the carb off and the bowl off the bottom, with the float installed, turn the carb upside down so the wieght of the float holds the needle in the seat and see if you can blow through the fuel inlet. Even better is use a vaccuum guage (like a mighty vac brake bleeder) on the fuel inlet and see if the float needle is leaking by.
zippy895
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zippy895 5/5/2011 12:11pm
5/5/2011 12:11pm
w/ the carb away from engine,gas line still installed or put longer one on ...removed bowl cover, hold bowl w/ hand so it is seated ,open petcock and find out whats causing the leak at seat area.
minidad160 5/5/2011 4:00pm
5/5/2011 4:00pm
I've had the issue with a cr125. It was an oring on the brass part that holds the main jet sorry don't know the correctname.

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