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Discussion Starter · #1 · (Edited)
Hi guys,

To clarify, this is not an “I didn’t use the search button and have no clue about the throttle body hose, fuel tank drain, or fuel filler gasket”. I am fully aware of the common culprits.

This is an attempt to itemize the steps to diagnose it in the event that the origin is not readily apparent (and further when the throttle body hose shows no signs of leakage when running or sitting and has been tested with UV fuel leak dye with negative result).

Here’s an overview of the circumstances and the efforts I’ve taken to figure out the issue.

Bike:
2005 SV650
Approx 5900 miles

History: largely sat the past 9 years. Went through the bike, changed fluids, fresh battery, new tires on sept 17th, etc. rode 1400 miles the past 8 weeks.

Symptoms: 1) fuel smell the past few weeks, probably 900+ miles.

2) Reduced fuel mileage from 158mpt to 127 miles most recent tank, however that may not be a causation based change.


Searched on here, common culprits for fuel smell appear to be the throttle body fuel line, and to check for fuel near tank drain. Also fuel filler ring seal

1) tank drain and around bike is clean. Zero leaks, confident that is not the source.

2) fuel hose between throttle bodies appears bone dry. Photos showed dust visible on metal armature underneath. I’m assuming if fuel dripped down, it would displace the dust and provide evidence that it is leaking. UPDATE Fuel treated with UV leak detector. Full length of the throttle body hose and connectors wrapped with gauze and then taped to readily absorb the smallest quantity of fuel for UV dye detection. Ran 2 full tanks for 226 miles nov 24 2021. No evidence of UV dye. Will replace for giggles (this test was more expensive than the replacement of the hose but I was after good reference info).

To clarify for anyone searching for answers that may not have been clearly articulated in past threads, these are the questions:

To test for throttle body fuel line leak:

Would evidence of the throttle body hose leak be visible while the bike is off (ex-drip/leak/we line while off) or just while running, as implied by the fuel pump? Don’t know enough about the system to know if that hose is pressurized when the bike stops. For my purposes, this no longer matters as I tested the lines with UV dye while running.

Next, may be the fuel filler seal might fail and create a fuel smell when riding?

So, if no fuel on the ground, no visible fuel dripping from the fuel line between the throttle bodies when sitting (and next checked while running), do we then point to the fuel filler seal?

And do we ignore a mpg variance as attributable to the highway cruise/speed/wind resistance vs a mechanical cause?

Trying to make a step by step list for others to reference as well.

Thanks for any help!
 

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I would just go ahead and replace the fuel line between the throttle bodies first. That is the most common thing--in fact, it's happened to me at least 3x in 10 years and 60k.

Especially if your fuel smell is only apparent while riding or right when you get off the bike, rather than when you first walk up to it in the morning.

Think about how bad a fuel leak you need to have in order to smell it while riding. If it were leaking that badly from somewhere not pressurized while running, then your tank would be empty overnight and your garage would stink.
 

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Bored Sunday morning poring through posts, found this one mentioning FI clamps. I've never heard of FI clamps. The SVR search engine lead me to old posts with pics removed. Finally, Dr. Google explained to me that FI clamps are Fuel Injection Clamps as pictured here:

Clamp
Automotive tire Bicycle part Gas Jewellery Automotive wheel system


No longer a boring Sunday morning. I'm going to replace all of my worm-screw hose clamps with FI clamps. Thanks guys.
 

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They’re ideal but overrated. I had to replace my original fuel line between TBs years ago. FI line from parts store cut to length. Worm gear clamps, and safety wired them. Worked perfect.
 

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Discussion Starter · #7 · (Edited)
Glad to see you were introduced to fuel injection clamps this morning Geo. I’ve been turning wrenches for a couple decades (opened my first small dealership in college with a friend by maxing out our student loans so we didn’t have to work min wage jobs in school). I still rebuild insurance wrecks to supply my never ending need for fleet vehicles but do not do it commercially nor do I enjoy it. I am a sucker for collecting older low mileage things with the intention on preserving them, with 11 currently stored in queue (also why I ended up with this 05 SV as it had 4k on it I couldn’t resist).

Joe, thanks for the advice, however I didn’t intend my post to reflect that I was unaware of the fix to the fuel line leak. My intention was focused on identifying and confirming the origin of the fuel smell.

As noted, a coating of dust was visible on the armature below the fuel line, giving the initial indication that no dripping fuel had displaced the dust, no fuel residue was visible, running a finger all around the existing clamp yielded no fuel smell on the finger. *Updated to reflect that 2 full tanks of fuel have been run with UV dye and the entire hose/clamp area wrapped with absorbent material and heat shield tape. No reaction to UV light after 226 miles over 2 tanks in 1 day with 7 destinations to give it time to cool. I’d consider that relatively conclusive evidence that this particular item is not presently leaking as it tested both cold and warmed up. Did it just because I needed to know, not because I didn’t want to replace it as what I did was both more costly and time intensive than just replacing it, but I wanted to be able to say that “sometimes when you smell fuel, it might be so slight of a leak that you get only a few drops per tank/cold start/etc…so even though there’s no evidence to the naked eye, here’s what it looks like”. Unfortunately it didn’t work out that way here, as I’d be willing to bet $500 that hose is not the source. It will be replaced anyway.

Asking the specific questions with regard to looking for evidence of the existence of that particular leak in hopes to document not only that it exists (which is already well know as you noted), but how to clearly identify the symptoms and in what fashion they manifest is was what I was after.

Naturally I’ll throw a couple clamps on it, and if I still have the fuel smell, the problem was elsewhere.

I was hoping to both verify its existence and create a diagnostic reference for active symptom detection, more for posterity and hopefully someone else’s benefit.
thanks.
 

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If the fuel line leak is bad enough you'll see fuel dripping on the ground at idle. Sometimes the leak can be affected by air temp, as in, it may only leak if it's cold, but once the engine warms up, the leak stops.

All other leaks are passive and should be detectable whether the bike is running or not.

Additionally, my gas cap seal is no longer liquid tight, and probably hasn't been for years. I never smell fuel around the bike from that area.
 

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Like a few others have said, replace the hose and clamps that connect the throttle bodies.
Mine leaked, but since the hose and clamps were replaced, not a drop of gas or smell of gas.
IMO, it's best to replace the short hose with FI rated hose, it's rated for higher pressure than regular fuel line.
 

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Discussion Starter · #10 ·
Like a few others have said, replace the hose and clamps that connect the throttle bodies.
Mine leaked, but since the hose and clamps were replaced, not a drop of gas or smell of gas.
IMO, it's best to replace the short hose with FI rated hose, it's rated for higher pressure than regular fuel line.
Thanks for the reply, and suggesting FI hose. In this instance, I was trying to create a step by step method to diagnose it. It appears that it came off as I failed to understand that the hose should be replaced.

My intent was to more clearly articulate what the problem may be and how the symptoms manifest to help understand vs. a “just replace the hose” approach, as that seems to leave the door open for subsequent questions down the line if it didn’t appear to solve the problem.

I was also hoping to build more of a symptom database for people to reference like:

1)if my hose is leaking, will drips be visible while sitting?

2) Does the line remain pressurized while the bike is off? (Indicating pressure vs no pressure and further elaborating on the possibility of visible drip).

3) For others that have had this fuel smell problem that was subsequently determined to be the hose, is it always readily apparent? Does it go away after the bike comes to temperature and the hose expands (so unless you test cold you’re less likely to be able to see evidence) further indication that the “finger test” of running your finger around the hose ends trying to get fuel on your skin may only work cold or maybe not at all yet you still may have a leak.

In my instance, the hose was tested with UV dye and an absorbent wrap over a series of cold and warm starts and ran for approx 230 miles yesterday with not even a drop of fuel indicated. Yes I’m replacing it. But the question becomes-what is the problem, since it’s highly unlikely that this is it.
 

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1) if the hose is leaking and the engine is cold, yes, you would see fuel dripping, but the hose commonly does not always leak all the time/every time.

2) yes, but only for a short time.

3) no, it is usually intermittent.

The problem is that you have 40+ psi fuel pressure being held in by a fixed clamp and a soft rubber hose. The hose over time and with heat cycles crushes slightly or breaks down/hardens so the clamping force of the fuel clamp no longer squeezes the hose tightly on the barb. When conditions are right (wrong?) the fuel leaks under pressure.

Believe me, I completely understand where you're coming from by trying to come up with a diagnostic tree, but the reality is you're overcomplicating the situation.

We have a known failure point with symptoms exactly as you describe--intermittent fuel leak.

You can do nothing and keep on trying to catch it in the act of leaking. Like I mentioned before, I was able eventually to catch the bike pissing gas as it warmed up, but I've also been 80 miles from home on the freeway with it leaking and ended up pushing the bike the last 1/2 mile to a gas station in the dark. I would've been really screwed if the bike didn't sputter until after I went by that particular off ramp. So you could be proactive and just replace the hose and clamps.

Since I've had to deal with the problem 3x now, I keep a spare piece of hose and a couple of clamps and a leatherman multi-tool in my tank bag.
 
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