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First Post: DRZ400s petcock... About to give up.

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I have an 04 drz400s, and a few weeks ago my friend (who knows a lot about this bike and has the E) and I pull the carb and checked out the jet kit the previous owner had done. It was all wrong and we got it all put right. I left town and he threw it all back together for me. While I'm out of town he is telling me it runs great. I get back and we go to start it and gas comes running out of the air box. So first thought is petcock failed. We clamped the vacuum line and let it run to see if it would die after a while and it didn't. I changed the smilly face gasket & large o-ring on the front. Then the small O-ring on the back. I found these gaskets on TT. I did not change the deframs because a. Seems you can't buy them & b. They looked to be in good shape.

I didn't notice leaks when I plugged the Vac line so I hooked it up and took off. Next day, bike is flooded again. I currently am using a C-clamp to shut off the gas. I know many will say switch to the non-vacuum style, but I like the vacuum. If I absolutely have to I will but is there something I'm missing? If I have to switch which is the best/cheapest non-vac petcock to switch too?

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seems to me your pal got the float stuck. you need to look at the carb again, not the petcock. my tank valve stated leaking and i had to replace it. but it wasnt flooding the engine, just my driveway. 👍

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I asked him and he said he set the float level and checked it. And the valve is fine.

So if the float was sticking it would still allow fuel to flow into the carb when the bike was off?

Edited by BFB62185

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So if the float was sticking it would still allow fuel to flow into the carb when the bike was off?

only on prime.

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Did you change the seat and the valve body O-ring?

I put a Pingle petcock on mine...when turn the key off my left hand automatically shuts off the fuel.

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The advantage of a vacuum operated petcock is it shuts off automatically. The disadvantage is it gives the fuel 2 places to leak past, the large selector seal and the "O" ring.

You need to do some more testing. If the carb floods with the motor off and the petcock set to ON or RES, it is a petcock problem regardless of if the float valve is good or not.

Disconnect both the fuel hose and the vacuum hose. Use a catch container and operate the petcock with a vacuum pump or just suck on the hose by mouth. Observe the result. If it seems to shut off, let it sit over night with the hose in a catch container. If it leaks past the shut off, you will have to determine if it is the "O" ring or the selector gasket. Surface finish is important for the metal parts that contact the seals.

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You need to do some more testing. If the carb floods with the motor off and the petcock set to ON or RES, it is a petcock problem regardless of if the float valve is good or not.

sorry to be blunt, but that is BS. the float and shut off needle close the fuel. the other stuff is good when parked, at an angle, whatever, it will not cause fuel to flow out the airbox or cause anything other than a little harder start, maybe. i am sure, like me, we have left it parked in "prime" with no drained fuel tank.

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sorry to be blunt, but that is BS. the float and shut off needle close the fuel. the other stuff is good when parked, at an angle, whatever, it will not cause fuel to flow out the airbox or cause anything other than a little harder start, maybe. i am sure, like me, we have left it parked in "prime" with no drained fuel tank.

you're at least half wrong here. a vacuum petcock flows fuel when there's vacuum applied to the diaphragm in the petcock. when there's no vacuum, the fuel can't flow. the needle and seat do stop fuel flow, however anything over 5 or 6 pounds of pressure will push past it depending on the condition it's in. if the OP has the bike on "on" or "res" and the bike is off and still flowing fuel, then Noble is right and there's a problem with the petcock. it's irrelevant whether or not the needle and seat are even in the carb for this post.

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mongoose - I think you need to re-read my statement in context. No BS. "If the carb floods with the motor off and the petcock set to ON or RES, it is a petcock problem". I am talking about a vacuum operated petcock here that is off when the motor is not running. If the motor floods with the fuel supposedly off, it is a petcock problem - simple as that.

The purpose of the float valve is to regulate and stabilize the fuel level in the carb. Sure, when the motor is not running the float valve needs to shut off completely to stabilize the fuel level. But is is not the design intent for the float valve to hold back fuel over long periods. Some will, some will not. If the gas is on and the motor not running and the carb floods immediately that is a float valve problem. The S carb makes it hard to tell if the float valve is leaking abnormally. But regardless of what the float valve is doing, if the gas is supposedly off (vacuum petcock set to ON or RES, motor not running) and the carb still floods, that is a petcock problem.

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sorry to be blunt, but that is BS. the float and shut off needle close the fuel. the other stuff is good when parked, at an angle, whatever, it will not cause fuel to flow out the airbox or cause anything other than a little harder start, maybe. i am sure, like me, we have left it parked in "prime" with no drained fuel tank.

I can only assume from what you posted you’re a young guy, or someone who has not been around motorcycles very long..

Your position is flawed, and erroneous. On several points.

Prior to vacuum operated petcocks, it was required knowledge to turn the petcock off after stopping the motor,,, not doing so was a guarantee to have a carb flooded upon return, and likely a air box and crank case full of fuel. This is not a guess, this is not something I read about on the internet.

Post vacuum operated petcocks, it is common for this same thing to happen, when the vacuum operated petcock fails to shut off fuel flow complete, for any number of reason.

A carb float bowl needle and seat is not designed, and often will not positively stop fuel flow when the petcock allows flow to the carb and the engine is not running.

This is not a guess, it is not just something I read on the internet.

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Okay

1. I have never once switched the petcock to prime since purchasing the bike. 2. If it is rubber and in the petcock, I have replaced it. When I did I used new fuel resistant rubber.

3. I'm almost sure it has nothing to do with the carb.

All I can think of is the two rubber deframs. (which they don't have replacements for). At this point I think I am just going to switch to a non-vac. Do I go with the wr400f petcock? And what should I use to plug my vac line?

PS. I'm broke

Edited by BFB62185

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.... And what shoulni use to plug my vac line. (I'm broke)

Any automotive store will have caps to block vacuum lines. If you are unsure of the size most stores offer a package containing various sizes, pick the one that fits the tightest. After loosing the first one I put on I used a zip tie to hold the second one on.

The rubber vacuum line goes onto a metal tube coming out of the right side of the Mikuni carb. Place the cap over that metal tube to block the vacuum line.

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BFB - I hate to give up so easily. You have a petcock problem, you have replaced some parts in the petcock, that did not completely fix the problem. It is worth looking at it again before you give up and replace it with a new petcock. As you posted early on, you would like to stay with the vacuum operated petcock and there is not that much to go wrong with the original. Take another look. Do some testing.

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Yes float valve can and do leak a little which is why we use vacuum operated petcocks or manual petcocks to shut off the fuel. It shouldn't be leaking enough to cause trouble overnight though. Having to shut off the fuel to prevent the fuel from draining into the carb overnight is a bandaide. By all means fix or replace he petcock for now, but you'll need to get back into that carb eventually because if fuel is leaking past the float valve that fast it's going to cause running issues as well, if not now at some point in the near future when it gets worse.

My KTM can sit for days with the manual petcock left on with no signs of fuel coming out the overflow. If the float valve is doing it's job that's how it should be.

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I have the same problem. I replaced mine with a WR400 petcock about a year ago. I wish the stock would still work. I tested it with the line off the carb and it leaked. Now with the manual petcock I have to remember to turn it off EVERY time I turn off the engine. In the 2 minutes it takes the fill up the at the gas stop it will flood the engine. I shouldn't have to change my oil after every ride.

I looked up a replacement needle valve since the cone-shaped o-ring is hard as plastic. You have to buy the assembly which is 4 parts, maybe. $53!!

Windblown, I know what you mean about the KTM. My 300 can sit for a month with no problem.

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lodom89 - I do not have the metric size for just the "O" ring but you can measure the old one and/or the "O" ring gland and order just the "O" ring from several on line sources. I use Air-Oil Products but there are others. Even with min purchase and shipping it is pretty cheap compared to buying the whole valve from Suzuki or SUDCO. I you have a well stocked auto parts or hardware store you may be able to find what you need for under a buck.

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Noble is right, they are not hard to find. Take the valve body O ring to a NAPA store and match it. They stock O rings that are fuel resistant.

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BFB, if you do replace the fuel valve I got one from a raptor for $16. I cant use it with my FCR because of where the line exits, but i think others have with good luck. You will need to use the washers from your stock bolts but you will need shorter bolts in order to make it work.

I guess from starting in motorcycles on Dirtbikes its not a big deal to turn the fuel on/off for me. Even though i still have a vac operated valve i check it every time i get off the bike.

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I had this same problem and went through mutiple petcocks before purchasing the E model, non-vac one. It's the right length and fits the best in my experience. The only thing I had to do was twist the nipple a little so it lined up towards the carb better.

I also noticed no one mentioned (unless I just missed it) that the vac operated petcock doesn't always fail in the same manner. Some have said it fails by not stopping the fuel flow into the carb in the normal direction (from fuel line to carb float bowl same as leaving a manual petcock in the 'on' position), but sometimes it fails and allows fuel to flow down the vac line to the carb effectively flooding the carb from the top down. This is what was wrong with mine. I suggest (for your sake) you pull both the vac line AND the fuel line from the petcock and see what's leaking. If you have a faulty petcock, you will surely get fuel out of one or both places. If you do, just do yourself a favor and get a manual petcock, you won't regret it...

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