03 XR250R won't stop randomly puking gas

The problem started probably a year ago.  The carb (stock Keihin) has been taken apart and cleaned numerous times after bits of the petcock rubber decided to migrate, replaced the petcock.  I am positive there are no bits left, every time I have taken it apart there aren't any.  Tried a couple new float valves.  Float level is spec.  It doesn't happen all the time, but if the bike sits for a few days it will start puking gas and I take the carb off, take it apart, nothing apparently wrong, put it back together and it will be fine for a little while.  Then, let it sit for a few days, go to start it up and its puking gas like there isn't even a float valve in there.  Float does not appear to be leaking either.  I'm baffled, and don't really feel like spending the money for a new carb, but it may be the only solution.

Edited by cjjeepercreeper

The plunger is new?
Float float float. But the float doesn't actually plug the gas. The plugers tip does. This is actuated by the float. Buy a keihin kit from Honda with all new rubbers in it.
Put new plunger in and double check float height.

5 minutes ago, notoriousE-R-I-C said:

The plunger is new?
Float float float. But the float doesn't actually plug the gas. The plugers tip does. This is actuated by the float. Buy a keihin kit from Honda with all new rubbers in it.
Put new plunger in and double check float height.

Brand new float valve, carb was completely disassembled and rebuilt after the problem with the petcock. This is actually the second new float valve. And like i said, float level is to spec. The baffling thing is this is random.

Btw, I've rebuilt dozens of carbs and never encountered this weird problem.

Gotchya. Take a q tip and valve lapping compound and buff the female seat the plunger sits in/on.
You know what you're doing otherwise. You find it cj

You're turning the petcock to OFF when not being ridden, right?

So this is happening with the petcock OFF? If so, disconnect the fuel line from the petcock and connect a test line, drain to a container. Make sure that where on the petcock you think OFF is, is actually OFF.

If this is happening when the petcock is left on, then like above, float valve and valve seat. Otherwise, make sure the gas cap is venting properly. Even with a good needle and seat, too much head pressure can push fuel past the needle and flood the bowl.

Make sure the fuel is actually coming from the inside of the carb overflow line and not from a hairline crack in the bowl, dripping off or running down the outside of the overflow line.

Edited by Trailryder42
16 minutes ago, Trailryder42 said:

You're turning the petcock to OFF when not being ridden, right?

So this is happening with the petcock OFF? If so, disconnect the fuel line from the petcock and connect a test line, drain to a container. Make sure that where on the petcock you think OFF is, is actually OFF.

If this is happening when the petcock is left on, then like above, float valve and valve seat. Otherwise, make sure the gas cap is venting properly. Even with a good needle and seat, too much head pressure can push fuel past the needle and flood the bowl.

Make sure the fuel is actually coming from the inside of the carb overflow line and not from a hairline crack in the bowl, dripping off or running down the outside of the overflow line.

Petcock on, I turn it off when parked.  New float valve, in fact second new one.  I did clean the seat.  Cap venting properly.  New petcock.  Yep, puking out the overflow, and when it starts it doesn't stop.  Like I said, this just does it randomly.  I think I need to take it apart again and examine the float valve seat with a magnifying glass.  I'm at a loss on this, every time I've ever seen a bike do this it was obvious what the problem was once disassembled. 

52 minutes ago, notoriousE-R-I-C said:

Gotchya. Take a q tip and valve lapping compound and buff the female seat the plunger sits in/on.
You know what you're doing otherwise. You find it cj

This is next once I examine the seat with a magnifying glass like I said in the above post.  I'm just really sick of removing that carb. :rolleyes:

Take a close look at the walls of the needle bore too.

And you know the sleeve of the float arm the the pin goes in? With the float in place and the pin installed, if the float is really sloppy, can be rocked side to side, back and forth, I think that's too much slop. You can squeeze that pin channel in the float arm closed just a touch, without being so tight that it hangs up on the pin, to eliminate a lot of that slop. 

I've had a few carbs, while trying to set float height, I'd set one side, check the other side and it was way off. Floats level with each other, not bent cockeyed from each other on the float arm. It was just the amount of slop in the floats pinning.

^^^^^good points very likely being an intermittent problem. also check the 2 posts cast in the carb body that the float pin sits in, the holes the pin go's in for slop/ware and the inner sides were the float sits if theres any groves or dags they can limit the range of movement on and off. also the tang on the float were the needles spring loaded pin sits. the tang can get worn causing the needle pin to catch on the edges on and off.  when you had the carb off did you put some clean fuel line on it turn the carb upside down and blow  to see if the needle and seat were sealing?

On 11/16/2017 at 10:33 AM, vicxr400 said:

^^^^^good points very likely being an intermittent problem. also check the 2 posts cast in the carb body that the float pin sits in, the holes the pin go's in for slop/ware and the inner sides were the float sits if theres any groves or dags they can limit the range of movement on and off. also the tang on the float were the needles spring loaded pin sits. the tang can get worn causing the needle pin to catch on the edges on and off.  when you had the carb off did you put some clean fuel line on it turn the carb upside down and blow  to see if the needle and seat were sealing?

Yep, all of that.  That's why I posted this here, its frustrating and baffling, but there are a couple things here I haven't thought of and am going to get to today.  I had thought of cleaning the bore with lapping compound and a q tip, just hadn't done it, but now seems the time.

Well,believe it or not it turned out to be MORE black rubber bits.  I have no idea where they even came from, that carb has been totally disassembled and cleaned several times, the petcock and fuel line are brand new,  I did check all the other stuff as suggested, all good.  I guess its time for an inline fuel filter, but I don't know how crap could get past the petcock filter.  I'm mystified, but at least its fixed and runs fantastic, I just got back from ripping some trails, that XR is a joy to ride with the 277 kit.

If the 350s petcock uses a rubber gasket internally, the rubber bits could be coming from there. It's not unheard of for those to deteriorate, and given the age of the 350, well........

11 hours ago, Trailryder42 said:

If the 350s petcock uses a rubber gasket internally, the rubber bits could be coming from there. It's not unheard of for those to deteriorate, and given the age of the 350, well........

LOL, its a 250 with a brand new petcock.  That's what started the original problem though, last year, 13 year old petcock rubber.  Its like there are still little bits hiding to haunt me.  But, that carb has been stripped completely down several times since then and thoroughly cleaned.  Hopefully a fuel filter will take care of any haunted bits for the future.

get a clear inline fuel filter so you can see the crap it collects. easier to know when to back flush and you can see just what is coming out of your fuel tank. fuel flow included. I have a clear inline filter on all my bikes. saves on a lot of carb cleans.   have you flushed the fuel tank?

how did you go did you get it sorted??

I installed an inline filter.  The 2 little bits I found this time must have been hiding somewhere going back to the disintigrating petcock rubber.  I can't imagine where they were hiding, though, that carb has been thoroughly cleaned and stripped several times.

they may have started out bigger and or one piece jammed in. with vibration and fuel flow they have worked there way out.  being that you had a buggered fuel tap not long ago would have been the first place I would have looked with your issue. glad you got it sorted though. and hope the fuel filter will stop this happening again.

I have to say it is interesting trying to diagnose a problem from the other side of the world with little info. good fun.

keep that beast thumpin:thumbsup:

1 hour ago, vicxr400 said:

they may have started out bigger and or one piece jammed in. with vibration and fuel flow they have worked there way out.  being that you had a buggered fuel tap not long ago would have been the first place I would have looked with your issue. glad you got it sorted though. and hope the fuel filter will stop this happening again.

I have to say it is interesting trying to diagnose a problem from the other side of the world with little info. good fun.

keep that beast thumpin:thumbsup:

The first thing that was done after the problem was found a while back was replace the petcock and fuel line.  The petcock rubber disintegrating is a known issue, especially with e gas.  We'll see how this turns out.

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