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2005 YZ250f carb drain leaking.... stumped!

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Just bought my first bike -- it's a 2005 yz250f.  It needs a few things but I knew the carb had to be gone through -- I completely disassembled it, ultrasonically cleaned it, replaced all the gaskets and put it back together with new jets.

 

It drip, drip, drips out of the carb drain.  Thinking maybe it was overfilling, I adjusted the float level from where it was (~12mm) to the spec in my manual, 8mm.  Now it does more than drip.... it almost runs out of the carb drain.  Thinking about this, I realize that now the bowl is filling up a lot more than it was previously.  Regardless, if I let the carb sit over night, the bowl completely drains.

 

I replaced the intake needle (the seat seems to be non-serviceable?)  I've cleaned out the drain screw bore and have checked everything else I can think of.

 

Any ideas/thoughts?

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You shouldn't mess with the floats. The seat is dirty. Get some meta polish and polish the seat with a q-tip should fix the problem.

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It could be:

Float set to high. Check and set per the manual. Do not just 'wing it'.

Damaged drain tube. Float bowl removed, you'll see a brass tube, that is the overflow vent tube that shares the drain line on the bottom of the carb

Damaged drain screw. Common from people cranking down on it. It should only have to be snug, the tip is tapered.

Damaged Drain seat. The may be fixable as jeredlee suggests but only if you have a ream of the correct taper. Often if it is damaged, the solution is a new float bowl.

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You shouldn't mess with the floats. The seat is dirty. Get some meta polish and polish the seat with a q-tip should fix the problem.

 

Drain seat or intake seat? 

 

 

It could be:

Float set to high. Check and set per the manual. Do not just 'wing it'.

Damaged drain tube. Float bowl removed, you'll see a brass tube, that is the overflow vent tube that shares the drain line on the bottom of the carb

Damaged drain screw. Common from people cranking down on it. It should only have to be snug, the tip is tapered.

Damaged Drain seat. The may be fixable as jeredlee suggests but only if you have a ream of the correct taper. Often if it is damaged, the solution is a new float bowl.

 

One more detail before I order a new float bowl and drain screw..... My float bowl has a domed decal that says "Boyesen Quick Shot" --- is that an aftermarket piece of some kind or is that stock on this bike?

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Drain seat where the needle for the float seats its brass and can tarnish. I had the same problem on my bike and polishing the seat fixed the problem .

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If it is the float needle seat, it can be polished but... the float bowl would not be drained if it were just leaking there. The fuel tank would be (because the petcock was left on too).

 

You can inspect the drain screw for damage, if not smooth, replace it.

You can try and smooth out the bowl wehre it seats.

The boysen decal is probably just for the AP cover. Or just a decal. Many get just the decal because it is cheaper ;) Post a picture of the float bowl.

 

I would not just run out and buy a new float bowl until you are positive the bowl is bad, they are expensive.

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Petcock is functional and the tank doesn't drain.  I leave the bike for a few hours, pull the bowl off and nothing comes out.  It seems/feels like the drain seat and screw are leaking.  Since I adjusted the float, I suspect it is overfilling but the previous problem of the drip...drip....drip is probably the drain screw.  I'll post photos tonight.

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By going from 12mm to 8mm you raised the fuel level in the bowl before the float shuts off flow by 4mm. I would double check that setting and be sure that 8mm spec is correct. And be sure you're taking your measurements from the proper points.

Edited by Trailryder42

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Here are some photos.....  I did have the float adjusted somewhat high.  I blew into the fuel intake this time and set it properly.  I still have the drip drip drip....

 

20151109_181450_zps7dhhcshy.jpg

20151109_181145_zpsackkg571.jpg

20151109_181127_zpsp0wmztnd.jpg

20151109_181121_zpsw2hyvqbe.jpg

20151109_181134_zps82wwxrby.jpg

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Can you set the bowl on a work bench on a clean paper towel, level it up, and fill it with fuel to about the correct level and just watch it for a few minutes and see if you can locate a leak....?

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Why are you showing us the float bowl cover ?

 

The bowl cover has nothing to do with leaking. It just holds gas.

 

The leaking from the oveflow tube comes from a float valve system that is compromised.

 

Corrosion, wear, missing parts, etc

 

You need to remove the float needle and POLISH the float needle cavity and seat. Then it will stop hanging up and sticking.

 

If you see ANY marks on the float needle rubbe tip, it is toast. Replace it.

If you can see ANY pits or marks on the seat, it is done. Over. Must be replaced.

 

They can be replaced, using a small slide hammer to remove the seat, and getting a new one from Sudco.com or hundreds of other places.

 

https://www.jdjetting.com/xcart/product.php?productid=224

 

FCR rebuild method

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild

 

Vital carb info

 

http://www.pbase.com/jdjetting1/keihin_fcr_manual_views&page=all

 

http://www.pbase.com/jdjetting1/image/35706511

Edited by KRANNIE
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Yup, just a Boysen AP cover.

 

Check the Allen bolt drain screw, ensure the taper still looks good and also (with a bright light) look inside to where it seats. Yuo can see looking at the area the wrench goes into that it has been manhandled.

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oh wait, it's leaking from the drain

 

my BAD

 

Hah!  I was going to say -- the fact that it keeps leaking until it's dry tells me that it's the drain and not the intake needle/seat.

 

I like the idea of filling it with fuel and watching to see what happens.  I'm going to try that!  I'll report back.  Thanks for all the help, guys!

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Damn! I can't even believe it..... Some monster overtightened the drain screw so bad it cracked the casting. Now where do I find a replacement bowl? The fiche doesn't even list a part #.....

rYvCD2e.jpg

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If you're looking at having to replace it anyway, you have nothing to lose in JB Welding the crack to see if you can salvage the bowl.

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Yes JB weld works fine, but you will have to fill it from both sides and re-drill the hole, most likely.

 

You can get bowls on ebay, or if you are in a pinch, I have several available for $60 each

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Sorry, but I kind of thought that was the problem.

Epoxy might work.

 

You can get a new bowl for 200 or less. You might find a person who ruined or wore out their cab but the bowl is still fine for cheap

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Yes JB weld works fine, but you will have to fill it from both sides and re-drill the hole, most likely.

 

You can get bowls on ebay, or if you are in a pinch, I have several available for $60 each

 

I'll try the JB option first and go from there.  Just curious -- are the 2002 - 2008 bowls all interchangeable?  I'm only seeing 07/08 ones on eBay -- they look slightly different but I'm not sure if they can be swapped over?

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