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Discussion Starter · #1 ·
Hey guys, I work on bikes on the side just for my own enjoyment. So I'm not quite the most knowledgeable here but I can usually get my way through different troubles I see.

However, I recently bought a completely stock 2000 SV650 that wasn't running. I rebuilt the carburetors, set the mixture screws back to 2.5 turns out, and tested the bike. The bike started, barely held an idle, had no power, and would shut off after giving it any gas (with or without the choke). So, I tried adjusting the idle RPM screw on the left hand side to no avail.

Next, I checked the spark plugs and they appeared to show a lean condition but showed good spark with an in-line tester and just from grounding the spark plug to the engine. So, I turned the mixture screws on the carburetors all the way to 4.0 turns out (I know it's overkill but I wanted to make sure it still wasn't lean). However, after putting everything back together, I could not see any fuel at all spraying into the carburetors... Until I opened the gas cap on the tank, then there was a tiny amount of spray into the carburetors but not even enough for the bike to start.

The bike still will start with starting fluid fine. I may be missing some other steps I tried, but does anyone have any recommendations for what to try next? I thought about putting a vacuum pump on the fuel petcock but I'm not sure how much pressure to put on it. Any help is appreciated!

TL;DR: bike is not getting enough fuel and I can't figure out why.
 

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I was going to suggest cleaning the carbs again (never a bad idea), but what you said about the gas cap tells me the tank vent is probably blocked, the tank could be rusty and/or full of crud that is blocking the fuel lines, and the fuel lines and petcock themselves could be on the dirty side.
 

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Discussion Starter · #4 ·
I actually did clean the carbs prior to buying a rebuild kit and then re-cleaned them while putting the rebuild kit parts on. They really do appear clean on the inside to me.

I will have to try checking the inside of the tank a bit better and to also check on the vent; however, if it were only the vent then I would have assumed that the bike would run once I take the cap off (which it does not). The carburetors still appear to not spray much fuel even when the gas cap is open.

That does give me an idea to fill the carburetor bowls with gas and disconnect the carbs from the tank entirely. I'm just not sure if that would work since I'm not knowledgeable about how the vacuum (or lack of) would affect the carburetor's performance...

I appreciate y'all's tips by the way!
 

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You probably have them clean enough. What many people miss are the tiny air and fuel passages running through the carb body. Easy for pieces of crud to get stuck in them, and very difficult to dislodge or dissolve…
 

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I actually did clean the carbs prior to buying a rebuild kit and then re-cleaned them while putting the rebuild kit parts on. They really do appear clean on the inside to me.

I will have to try checking the inside of the tank a bit better and to also check on the vent; however, if it were only the vent then I would have assumed that the bike would run once I take the cap off (which it does not). The carburetors still appear to not spray much fuel even when the gas cap is open.

That does give me an idea to fill the carburetor bowls with gas and disconnect the carbs from the tank entirely. I'm just not sure if that would work since I'm not knowledgeable about how the vacuum (or lack of) would affect the carburetor's performance...

I appreciate y'all's tips by the way!
If you spray some volatile mist into the Carbs like WD40 or Carb/Brake cleaner see if the engine runs. When you did the carbs did you check and reset the Floats ?

Does fuel flow from the tank if you take the fuel hose off and suck and nip the Vacuum pipe.



Download and keep this picture as a reference,

 
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I will have to try checking the inside of the tank a bit better
My tank showed no signs of rust. And my white inline fuel filter showed no signs of rust. But when I drained my gas into a clear bowl and let it evaporate, the rust showed its ugly face.

Good Saturday Gone Bad---long post

Check out post #116 in this thread for pics. After I cleaned my tank and lined it with POR15, no more problems. She's been running great ever since.
 
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Discussion Starter · #9 ·
You probably have them clean enough. What many people miss are the tiny air and fuel passages running through the carb body. Easy for pieces of crud to get stuck in them, and very difficult to dislodge or dissolve…
This may be the exact cause then. When I've taken the carbs off the bike I have made sure to notice that there is plenty of fuel in each bowl. So I'm thinking it must be an issue with the carbs or possibly vacuum? I'll take them out again and try looking for the tiny passages you're referring to.

If you spray some volatile mist into the Carbs like WD40 or Carb/Brake cleaner see if the engine runs. When you did the carbs did you check and reset the Floats ?

Does fuel flow from the tank if you take the fuel hose off and suck and nip the Vacuum pipe.



Download and keep this picture as a reference,

Thank you for sending the picture, I appreciate it! I'm not sure if I'm understanding the first part of what you're asking. If you're asking whether the bike will run when the carburetors are hooked up and you spray fluid (like WD40 or starter fluid) through the carburetor, then yes, it will run for a quick second before turning right back off. Also, I have checked and double-checked the floats. They appear to be in spec. Also yes, gas does flow from the tank, through the first hose, fuel pump, and second hose. Like I mentioned in the first reply on this post, the carburetors do have fuel in the bowls. So I'm thinking that the fuel issue is after at least the fuel pump unless if it is some issue with vacuum?
My tank showed no signs of rust. And my white inline fuel filter showed no signs of rust. But when I drained my gas into a clear bowl and let it evaporate, the rust showed its ugly face.

Good Saturday Gone Bad---long post

Check out post #116 in this thread for pics. After I cleaned my tank and lined it with POR15, no more problems. She's been running great ever since.
I'll have to try that out this weekend! I know it is new/good fuel but I'll try checking it to see if it has a lot of rust in it once it evaporates. That post you referenced is crazy, that's a lot of rust!
 

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It was a lot of rust. And I disregarded rust in the tank as my root problem because I saw no rust, and my clear white inline filter was perfectly clean. But after evaporating (over a few days) about a quart of tank gas in a clear glass bowl, my problem showed herself.
 

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I'll take them out again and try looking for the tiny passages you're referring to
Everything with a hole in it required a strong blast of carb cleaner. And seek where it comes out the other end. If it is not coming out somewhere, it's probably clogged. After getting clear streams of carb cleaner from EVERY passage, hole, port, etc., blow it all out with compressed air. BTW, I did this twice, just to make sure each passage was spotless. Refer to:

Dangers of a Lo-Carb Diet

It helped me immensely. The pics no longer show, but Ziptech's writeup is very thorough.
 
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Thank you for sending the picture, I appreciate it! I'm not sure if I'm understanding the first part of what you're asking. If you're asking whether the bike will run when the carburetors are hooked up and you spray fluid (like WD40 or starter fluid) through the carburetor, then yes, it will run for a quick second before turning right back off. Also, I have checked and double-checked the floats. They appear to be in spec. Also yes, gas does flow from the tank, through the first hose, fuel pump, and second hose. Like I mentioned in the first reply on this post, the carburetors do have fuel in the bowls. So I'm thinking that the fuel issue is after at least the fuel pump unless if it is some issue with vacuum?
Start at the Petcock. Take the Vacuum line off and suck on it and nip it like the photo. Then pull the fuel pipe off the Petcock and does the fuel flow? If not then there's a problem with the Petcock.

Also use the forum search for posts on a clogged vent/ pipe at the fuel filler orifice. It has been known that if there is no air allowed into the tank because the venting is blocked it can cause a partial vacuum that will impede the fuel flow.
 
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