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gas in engine after petcock rebuild

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i rebuilt the petcock, replaced all the gasket and what not because the petcock was leaking and flooded the engine (gas in oil, bike not starting....)

i cleaned my carb too since it sat in the garage for a few months not running.

it fired up nice and easy last night like it always has.

now when i tried to fire up this am.....the top end is once again full of gas!!!! now i need to flush the whole thing again. 

WTF????

what did i miss???

 

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The petcock is only half the problem , the second half is the o-ring under the needle valve in the carb . When you take your float out there is a pointed needle with rubber tip, that goes down into a brass plug that's held in by a small screw. That plug needs to be taken out and under it is an o-ring , that is what lets fuel leak by , basically bypasses the float needle and seat.

Look at part #18 , the o-ring is with that assembly , but you can get the o-ring separate if the needle-n-seat is in good condition otherwise you can get the whole assembly and start with new again . http://www.partzilla.com/parts/search/Suzuki/Motorcycle/2006/DR-Z400S/CARBURETOR/parts.html

Ebay has aftermarket that are cheaper but usually the o-ring is all that's needed , I like to start with the whole assembly if it's been 10-12 years old already.

 

 

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Edited by jjktmrider
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thanks for the reply.

that makes sense. of course that's the only one i didn t check :banghead:

i checked the petcock again and it actuates the way it's supposed to when you pull vacuum.

however, at rest, there is a very very tiny amount of air leaking thru (when you blow in it) is it suppose to let out a small amount after a rebuild?

i even cleaned and "buffed" the seat for the oring, replaced the spring an it did not make any difference.

do i need to order another rebuild kit??? seems like the only defective part is that oring in the rebuild kit. can you get that somewhere separate?

Also maybe a stiffer spring?

 

thanks

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The key elements of the petcock are the O ring on the end of the plunger operated by vacuum and the selector seal under the lever.  Either one or both can leak to allow fuel to pass.  When working properly the petcock should not leak at all.  The O ring on the plunger is the usual suspect when the petcock leaks.  There is very little pressure from the spring seating the O ring.  O ring material, condition and size arecritical.  I don't know anything about the quality or reliability of the rebuild kits.  Some people just instal a $10 in-line shutoff valve after the tank petcock. Some people replace the vacuum operated petcock with manual, some people buy a new Vacuum petcock.

Yes you also need to deal with the carb float valve.

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Is this a Mikuni problem only ? Could it happen with Fcr ? Or would the Fcr leak on floor . 

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Regarding the o rings and fuel valve seat, Are there two separate O rings that go in there or is it just the one that goes around the valve seat? There is also a little dome shaped piece that goes at the same end which I assume is s fuel filter of sorts? 

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There is just one o-ring ,7.8mm x 1.7mm or something close , 5/16 x 1/16 works though a bit tight . That dome piece is indeed a filter , I like to use them but others throw them out because they tend to plug up , but that's what they're for , thus why I use them if not an inline filter . Just an option , up to you .

 

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Edited by jjktmrider
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i finally decided to replace the stock pos with the Yamaha 5LP245000100 Fuel Cock Assembly

The hell with their "safety feature" of having the fuel always on when you start the bike; what's the point of having a bike you won t ride because you don't trust? 

i never had this vacuum nonsense on my other bikes and never had a problem anyway,

i also found a Carburetor Repair Kit on amazon:

All Balls 26-1107 Carburetor Repair Kit (26-1107 Kawasaki KLX400SR 2003 and Suzuki DRZ400S/SM 2000-2014)

that contains the oring and float valve needle and seat for 1/2 the price. we'll see how that works.

 

thanks for all the replies, i hope to get it running next week.

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I went ahead and installed that filter considering I had a brand new one and removed an old brittle one from the original. Seat. It wouldn't hurt to also run another fuel filter from the tank to the carb would it?

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There are quite a few of those filter ends on stock petcocks inside the tank that are brittle from age and all broken up or simply washed off from sloshing fuel so that little filter is a last stand against junk in the carb that plugs jets or causes a stuck needle valve and gas pouring on the floor or into the motor. 

 

Scheckaet , if you have the stock steel fuel tank those Yamaha petcocks don't fit very good with the Mikuni carbs and I won't suggest one . The outlet comes out right against the carb and the hose ends up either kinked or having to do some goofy around the carb , in -out, up-down-around and through jumbo , yet still not right . A down outlet version is the way to go , even one that comes out forward is better . YZ125 petcock is one that comes out down(but most only have on/off no res, there are a few aftermarket version with res though) or there is one on ebay that I have , though it is a Chinese model , so not perfect but it has been working fine .

http://www.ebay.com/itm/OEM-FUEL-PETCOCK-ASSEMBLY-WITH-RESERVE-YAMAHA-YZ125-YZ250-YZ-125-250-1989-2015-/322496476420?fits=Make%3AYamaha|Model%3AYZ125&hash=item4b1649b504:m:mkdLqqse9up6AR-966_uH9g&vxp=mtr

 

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Edited by jjktmrider

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