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Throttle Loss at Cruising Speeds

1K views 4 replies 3 participants last post by  WintrSol 
#1 ·
I'm riding a 2008 Suzuki Boulevard C50 and recently had some issues on the highway. When going above ~50mph the bike will occasionally lose power (throttle down) and then sporadically kick back in. When it's throttling down it doesn't respond at all to my throttling unless I release it completely. I ended up needing to pull off and take the back roads because I couldn't keep up with traffic and the issue only seems noticeable while at higher speeds. The bike is fuel injected and I'm not getting any DTCs. Below is the FI system wiring diagram for reference. At first I was thinking TPS but I figure I'd get some fault codes. Any thoughts are appreciated.
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#2 ·
Is there an inline fuel filter? Someone may have added one and it could need a replacement. There may also, and let's hope not, be a screen in the tank that is getting plugged up with gunk these new fuels like to make. That's my best shot at it.(y) (y) (y)
 
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#3 ·
I believe there is but Suzuki doesn't seem to be very clear on this for the C50.
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This whole assembly is in the tank and I replaced the pump portion and mesh filter last year. I tested fuel flow at the time and it passed (messy job). It's a bit harder now since I can only reproduce the issue at cruising speeds. Barring any other suggestions my next step will be to pull this assembly (again) and check for debris.
 
#4 ·
If no other inline filter then the only positive way would be to remove an inspect for the gel that these new fuels create today. It does sound a little like fuel starvation to me anyway. I honestly don't know if a heavy dose of Seafoam or other such products would break down that possible film or not. It would require multiple tanks and you state you can't get up to good cruise speed so it would take a long but it might help. I just know about that gel though. A little varnish is one thing and it works for that I don't know about that gel that may have formed in there. Maybe someone been down this very road and can say for certain one way or the other. I sure can't.
 
#5 ·
Don't assume it's a fuel problem; I suspect you may get a code for that. How about cleaning the run/stop switch, and making sure the spring in there is strong enough to hold it closed? It could also be the side stand switch, the spring that holds the side stand up, the pivot for the side stand needs cleaning and/or lubrication, or the side stand relay, which are known issues.
 
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