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Fuel / Pump / Throttle issue?

15K views 16 replies 7 participants last post by  Kcrook101 
#1 ·
Hey all

So I've been chasing this problem for about two years now. It's one of those sporadic issues that the bike does it, you take it to the shop, they have it for a day and it never shows up. Then I take it home and two days later it happens again.

The main symptom is the bike running sluggish for a period of time. now for the details.

Picture yourself having a drink from a bottle, the contents of which, I'll leave up to you. Bottoms up, that glug glug when you drink, let air in, drink more, let air, etc.


  • With the throttle open that is what the bike feels like: rev, pause, rev, pause. It migt be subtle enough not to hear it much but you'll feel the bike rocking a bit forward and back as it pauses for the slightest moment. If it's bad enough it might sound like I'm running on one cylinder even.
  • When this happens, if I clutch all in or leave it on neutral and rev it up maintaining for a few seconds I'll get a couple backfire pops
  • If I engine brake I might get a few backfire pops
  • If I'm slowing down and let the throttle hang around between just before accelerating and letting the throttle go, it might get a few pops as well
  • Sometimes this will clear it up and I can keep going with no issues, sometimes I'll need to pull the choke out to alleviate until it gets over it.
  • If it is in the middle of this ... asthma atack, for lack of bettter description, and I need to come to a stop, sometimes it will just die on me unless I pull the choke out to keep it alive.

Recently I took the Carb out and had it all cleaned up. Since then it feels like it picked up a new symptom. Lets say im doing 50mph

  • it's having the fit
  • Throttle down
  • Throttle up, nothing happens
  • throttle reaches about where it was to maintain my speed and it kicks back

While it'll do the other symptoms, after having the carbs cleaned, it feels like the symptoms are more organized with the addition of the new symptom.

At this point the shop has mentioned that it might be a fuel pump issue. That, with a full tank, bypass the pump and go to the carb. It should let me ride around for about the first gallon or two aided by the weight of the gas before needing the pump. If the problem doesn't happen then I might have the issue there. The only problem is that the symptoms can show up every day this week on my way to work, and just the one day next week. I might go a full tank with the issues not showing up and next fill up, it might show up after a few days of riding. My paranoid self at this point has started to, probably falsely, notice that if there is a crosswind, chances are higher for the problem to occur.

I've cleaned carbs, changed vacuum lines, put a fuel filter between tank and pump. I' had to even swap out the engine (completely different issue), and the problem survived en engine swap. Needles to say, this is a frustrating problem and I'd rather not keep swapping $100 parts to go deeper down the rabbit hole of an elusive problem.

/rant :blackeye:

Thoughts? Ideas?
 
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#2 ·
The fuel pump in the Volusia is vacuum operated. If you are getting intermittent fueling, then the issue is either with the vacuum source or the fuel pump itself. Inside the gas tank is a vacuum operated diaphragm. These do wear out with time and can cause issues similar to what you are experiencing. Since you have already ruled out vacuum by replacing both the lines, remaining source would be the diaphragm in the fuel pump or possibly a vacuum leak in the carb itself.
 
#3 ·
Any way to further diagnose which side of the equation is most likely to be the problem? I've browsed around for a used fuel pump that i could cheaply drop in and test but not sure if i would trust a used one if age is a factor.
 
#4 ·
The fuel pump operates under positive/negative pressure caused by the crank case.

Info is found here:

 
#6 ·
Alright. So I did some testing and sadly I'm at the same spot.

Tested vacuum lines to the pump and petco with bike running and there is pull.

Tested the vacuum on the pump before the carb, it holds the vacuum. Tested it at the petco valve and it holds.

Tested fuel flow at the petco with the vacuum connected and disconnected and it flows and doesnt flow respectively

Havent tried testing with the hose disconnected from the carb see how the flow is there so I'll probly try that next but it doesnt seem so far that the issue is fuel pump related. I did remove the inline filter from petco to pump cuz it did seem a bit cracked and its been there for a while anyhow, will see if that makes any difference on a ride longer than a few miles.

The hunt continues.
 
#7 ·
Didn't I read about a fuel cap issue causing similar problems?
if you've swapped engines, and the problem still exists, it most certainly lies in the bike, and the tank would be my first inclination. Cap, pump, lines, float etc.
 
#12 ·
Took a longer route home, bout 12 miles or so rather than the straight 8 and with a stop in the middle for a short errand (which sometimes would trigger the issue on the second leg of the trip). The problem did not pop up.

Considering how elusive the issue is, I'll keep running with the cap loose for at least one whole gas tank and see what happens. I might also try to run with the cap fully on for a few trips see if it comes back, and then leave it loose again and hope for it to go away.
 
#14 ·
Update so far.

Was out of town for a bit and it's also been raining quite heavily so haven't had the chance test ot much except for the past few days. Been running with gas cap loose and havent had the issue so far so the hypothesis is looking good so far.

I'll keep running like this for the remainder of the gas in the tank and see. If this were the issue, what's the best way to approach it? is it easy enough to find a cap for the '02 Intruder? how do I go about keying it or is the lock easily swappable? I haven't looked closely at it.

-S
 
#15 ·
So I think I've ruled out the gas cap being an issue. I've run it quite a while with it loose and the problem will come back every so often pretty badly. My work/home commute is now about 20 miles (moved recently) so it has gotten quite frustrating when it does it and Im still 10 miles from home having to wrestle the bike back through endless sputters and backfires. A shame cuz I really want to enjoy my new commute, longer but the ride is great.

Yesterday I decided to try out the test my shop suggested months ago which was to bypass the fuel pump and go straight from petco to carb. With a full tank, weight should be enough to get gas to the carb so I ran it idle for about 10 minutes or so, hopefully enough time for the carb to want more fuel from the tank. It ran fine like that until I decided to take it for a spin around the neighborhood to test it out before going for a longer ride. About 20 seconds out the problem came right back up so I just turned aroudn and went back in.

At this point I'm thinking theres something wrong with the carb, maybe stuck float? I had taken the carbs out and had the shop clean it so one would assume that would not be the issue but nothing else makes sense.

The it-still-runs article below mentions most of the symptoms I experience but I dont want to jump to conclusions. I'm running out of options other than test it by finding a carb on ebay and putting it in.
https://itstillruns.com/signs-symptoms-sticking-carburetor-float-7798023.html
 
#16 ·
I've been reading this Thread and it sounds a lot like the same issue I currently have. Did you finally get it working? if so, what was the issue..

After spending about $1,200.00 and still no fix. I finally took it to the dealership. Hopefully it wont hurt to sit down after they get done.

Thanks.

2009 Suzuki Boulevard C50
 
#17 ·
I've been reading this Thread and it sounds a lot like the same issue I currently have. Did you finally get it working? if so, what was the issue..

After spending about $1,200.00 and still no fix. I finally took it to the dealership. Hopefully it wont hurt to sit down after they get done.

Thanks.

2009 Suzuki Boulevard C50
I am having pretty much same issue did you find the cause?
 
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