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Discussion Starter #1
Anyone know why when my 1st gen sv650 is OFF the cyclinder head is loading up with gas. Even dripped its way through the exhaust pipe. I did the heads recently but the problem existed before that. Dean
 

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It could be a couple of things.

1st gens are carburated if I recall and later are F.I.

Primarily I believe the petcock for the bike is defective. I think it's vacuum operated and if broken and sticking on then the fuel will run into the carbs all the time. You can test the petcock theory by removing the fuel line into the carbs and see if it leaks with the bike off. Remember fuel is flammable and take the appropriate safety precautions! :)

You may also have a bad float valve in the carb bowl which will leak fuel from the bowl all the time. If they are fine then it's another issue in the carb, perhaps in the choke circuit.

I'd still lean towards the petcock as if it's supposed to be off and stop fuel when the bike isn't running, then it's not working even if the carb has an issue. Looking at some photos I think this is it:

122173


Assuming the setup is similar to my zr7s (it may not be) you may also want to make sure the cranckase hasn't filled up with fuel as well. It's possible it's run thru the vent lines / airbox into the crankcase.
 

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I"m not certain if you can get a rebuild kit for those or if you have to replace the entire petcock. Seeing the 4 Phillips round head bolts by the vacuum line leads me to think you can get a rebuild kit if that's the problem.
 

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Discussion Starter #4
It could be a couple of things.

1st gens are carburated if I recall and later are F.I.

Primarily I believe the petcock for the bike is defective. I think it's vacuum operated and if broken and sticking on then the fuel will run into the carbs all the time. You can test the petcock theory by removing the fuel line into the carbs and see if it leaks with the bike off. Remember fuel is flammable and take the appropriate safety precautions! :)

You may also have a bad float valve in the carb bowl which will leak fuel from the bowl all the time. If they are fine then it's another issue in the carb, perhaps in the choke circuit.

I'd still lean towards the petcock as if it's supposed to be off and stop fuel when the bike isn't running, then it's not working even if the carb has an issue. Looking at some photos I think this is it:

View attachment 122173

Assuming the setup is similar to my zr7s (it may not be) you may also want to make sure the cranckase hasn't filled up with fuel as well. It's possible it's run thru the vent lines / airbox into the crankcase.
Hello, I want to thank you for your response. My first inclination was turn off the gas. Interesting, I had changed the petcock a while back. I don’t remember the issue happening at that time. Then the petcock, new part, started leaking. So I used the gasket and filter and put them on the old one and put it back in. Pardon my ignorance, what’s F.I.? That’s a quick test and will give it a try.

Vacuum? does the choke work off vacuum as well. The choke is not working. And of course the bike runs rich because it is always partially on. With the season ending I should rebuild carbs?

Last time this happened I dropped the oil and it was filled with gas. I will do the same again.

This can be a multitude off problems. Vacuum and faulty parts. This bike had all original parts until I started restoring it and was left outdoors for most of it’s life. Thanks again, I have some work to do. Dean

P.S. That pic shows the setup to be exactly like mine.
 

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F.I. stands for fuel injection. A quick checked showed later versions of the SV650 to be fuel injected vs carb'ed.
Gen1's did not have fuel injection.

I have an 04' Kawasaki zr7s so this is how my bike works. I haven't looked specifically at yours but I assume they are similar.

From the photo above there are 2 hoses. One is the fuel line that goes from the tank down to the carbs. The other hose is a vacuum line, likely also coming from the carbs. When you go to start the bike the bike starts with the fuel that sits in the bottom of the carb float bowls. This creates a vacuum condition (as the engine draws in air/fuel) There should be a hose that runs from the carbs up to the valve pictured above. This vacuum in the hose then "turns on" the fuel valve and lets the gas flow down the other hose to the carbs like it should. Now if that part if broken, and sticks open, the fuel will be able to run down to the carbs all the time, even when the bike is off. This can result in the fuel leaking out of any opening in the carbs into the normal air/fuel mixture path and into the engine head, backwards into the airbox, and then into any open vent lines from the airbox to the crank case (or past the engine rings into the crank case.) When that's full it could leak out the exhaust, down the header and into the exhaust as it's the lowest point - then out onto the floor.

As for the carbs, if you've ever seen one apart, they have a float bowl at the bottom. It has a float that attaches to a needle that lets fuel in when low and stops it when full. If the carbs (or even just 1 carb) has a bad float or float needle, it can stay open - resulting in gas continually flowing into the bowl, and then out everywhere as per above. But, you'd have to have a bad petcock above to be passing fuel even when the bike was off.

Now you could have a bad petcock, and the floats are all fine, but if the choke is bad it could allow fuel to pass thru that part of the carb that is an extra bypass to the bowls, and voila you have a "leak" that causes the fuel to go everywhere again as per above.

Without digging into exactly how your bike works, it may be as simple as the 2 hoses on the bottom of the tank are mixed up (they look the same size) but I don't think the bike would run properly if that was the case (there shouldn't be enough fuel getting into the bowls if it was...)

Assuming there are no other petcocks on the bike the quick fix could be just to put a shut off on the fuel line between the tank and the carbs.

As to your request about the choke working off a vacuum, it shouldn't. Usually it's a cable than runs down to a slider that moves 4 plungers (or 1 plunger per carb if you have less/more carbs) and enriches the air/fuel mixture. This can be done a couple of ways depending on the carb, but most commonly by adding extra fuel bypassing the float bowls. So if nothing else that's why it's running rich - extra fuel when running.

As for should you rebuild the carbs, that's up to you. If that's what needed to fix the choke, then yes. Running rich isn't great. If you feel confident to do it yourself, or you want to pay someone else, then at the least take them apart and inspect them. There are lots of how-to's about cleaning carbs. I've done my 3-4 times and it's not hard if you are up for it.
If you've never done it, just do one at a time, take photos or videos, so if it's not right you can look at the photos/videos or compare it to the other ones, plus you won't mix up parts that may not be the same on each carb.

This is a quick nutshell, simplifying stuff, as it applies to my bike and many others. If yours is different I appologize for leading you astray.

Here's a video kind of condensing what I've said :) I should have given you this first right?

 

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Discussion Starter #7
F.I. stands for fuel injection. A quick checked showed later versions of the SV650 to be fuel injected vs carb'ed.
Gen1's did not have fuel injection.

I have an 04' Kawasaki zr7s so this is how my bike works. I haven't looked specifically at yours but I assume they are similar.

From the photo above there are 2 hoses. One is the fuel line that goes from the tank down to the carbs. The other hose is a vacuum line, likely also coming from the carbs. When you go to start the bike the bike starts with the fuel that sits in the bottom of the carb float bowls. This creates a vacuum condition (as the engine draws in air/fuel) There should be a hose that runs from the carbs up to the valve pictured above. This vacuum in the hose then "turns on" the fuel valve and lets the gas flow down the other hose to the carbs like it should. Now if that part if broken, and sticks open, the fuel will be able to run down to the carbs all the time, even when the bike is off. This can result in the fuel leaking out of any opening in the carbs into the normal air/fuel mixture path and into the engine head, backwards into the airbox, and then into any open vent lines from the airbox to the crank case (or past the engine rings into the crank case.) When that's full it could leak out the exhaust, down the header and into the exhaust as it's the lowest point - then out onto the floor.

As for the carbs, if you've ever seen one apart, they have a float bowl at the bottom. It has a float that attaches to a needle that lets fuel in when low and stops it when full. If the carbs (or even just 1 carb) has a bad float or float needle, it can stay open - resulting in gas continually flowing into the bowl, and then out everywhere as per above. But, you'd have to have a bad petcock above to be passing fuel even when the bike was off.

Now you could have a bad petcock, and the floats are all fine, but if the choke is bad it could allow fuel to pass thru that part of the carb that is an extra bypass to the bowls, and voila you have a "leak" that causes the fuel to go everywhere again as per above.

Without digging into exactly how your bike works, it may be as simple as the 2 hoses on the bottom of the tank are mixed up (they look the same size) but I don't think the bike would run properly if that was the case (there shouldn't be enough fuel getting into the bowls if it was...)

Assuming there are no other petcocks on the bike the quick fix could be just to put a shut off on the fuel line between the tank and the carbs.

As to your request about the choke working off a vacuum, it shouldn't. Usually it's a cable than runs down to a slider that moves 4 plungers (or 1 plunger per carb if you have less/more carbs) and enriches the air/fuel mixture. This can be done a couple of ways depending on the carb, but most commonly by adding extra fuel bypassing the float bowls. So if nothing else that's why it's running rich - extra fuel when running.

As for should you rebuild the carbs, that's up to you. If that's what needed to fix the choke, then yes. Running rich isn't great. If you feel confident to do it yourself, or you want to pay someone else, then at the least take them apart and inspect them. There are lots of how-to's about cleaning carbs. I've done my 3-4 times and it's not hard if you are up for it.
If you've never done it, just do one at a time, take photos or videos, so if it's not right you can look at the photos/videos or compare it to the other ones, plus you won't mix up parts that may not be the same on each carb.

This is a quick nutshell, simplifying stuff, as it applies to my bike and many others. If yours is different I appologize for leading you astray.

Here's a video kind of condensing what I've said :) I should have given you this first right?

Hello, I have to Thank you again for your detail and knowledge. I do posses mechanical skills but clearly didn’t understand the principals you have relayed. Understanding will take me a long way other than "figuring out". I will start with the quick test on the petcock as you suggested above. That makes the most sense.

Okay, so the choke is mechanical. I may have to open it up (carb) just to see all the working parts. There is an issue there than. When I pull the choke back on the handlebar while looking down into the carbs the plungers do not move at all. Running or off. I took the cable off where it connects to the carb and it has total mobility. Full range. So what ever is happening it must be happing in the carb.

I’m following the bowls and the floats thoughts. I learned some principals from my lawn mower. lol
I think it would make sense go from the top down.

Again, I thank you so much for taking the time out to help. I’m new to this Forum and “Wow”. Just printed your notes to bring with me over the weekend. Dean
 

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Discussion Starter #8
Hello again, I think it’s safe to say the petcock is defective like you had suggested. See attached photo with the bike off. The crank case and exhaust were full of gas as well. When I fill it again with oil I thought I would run it for 100 miles and change the oil again getting any contaminants fully out. Let me know if you have any additional thoughts on that. Should have the part and back on the road for the weekend. Thank you again, you saved me a great deal of time!!!
 

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Well glad to help, and sorry you've got a fix or two to do. (petcock now and the broken choke down the road)

When you drain the oil I'd be tempted to let it sit for a bit to allow any fuel to evaporate, and/or blow air thru the oil filler hole and let it come out the drain/filter hole, the same as I'd remove the exhaust and make sure it's drained / empty too. Starting it up with fuel in the exhaust could result in a backfire that damages the exhaust or a flamethrower that lights nearby items on fire. (ok, so this may be unlikely but you never know....)

Some of the others here who've had failures and filled the crank have drained the fuel/oil mix, did a fill with cheap oil, then drained that and refilled with proper oil without driving it. Your 100 mile suggestion is likely a fine idea as well. The goal is to 1.) get out any residual fuel that will thin the oil, and 2.) get out any crud that was happy in the nooks and crannys of the engine oil that the fuel thinning as set free :)

Again if you were worried you could always put in a fuel valve inline with the hose. Something like this: https://fortnine.ca/en/motion-pro-inline-fuel-valve-3-16-inch-od-barbs-08-0038?gclid=EAIaIQobChMIuMispPav5QIVCY7ICh0QfgQbEAQYCCABEgJjRfD_BwE

122185


Not sure if that's the proper hose diameter - it's more just for reference.

A valve is only a few dollars and may be cheaper insurance than losing a tank of fuel, jug of oil and a new filter in the future should a failure happen a third time!
 

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Discussion Starter #10
Yes, I dropped the exhaust pipes and allowed the motor to air out. There was about a cup of fuel in the lower pipe itself. I hand Rotated the motor to get every drop out. I had the same fears of a flame thrower exhaust pipe igniting my garage.lol. I ordered the shut-off. Although everything is tucked up tight and hard to reach I would feel better knowing the fuel is “shut off” when I’m away from home. Worth the little effort. Thanks again!!
 

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Glad to help!
 
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