Power loss under load

Squeaky back brake? Hard to control at 30mph/40kph?
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seh750
250cc
250cc
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Joined: Thu Apr 07, 2011 10:57 pm
Country: USA
City: Beaverton, OR
Year: 2011
Colour: White
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Power loss under load

Post by seh750 » Wed Jul 27, 2016 5:45 am

Did a 1300 mile ride across Oregon, Washington, and Idaho this past weekend. Had a great time except about 120 miles where my 2011 SMT ran horribly.

Bike has about 28,000 miles now. I purchased it new. It has Wings non-cat exhaust, secondary air removed, and a tune I downloaded online and loaded via TuneECU. It's been setup that way for over 20,000 miles and has been running great.

After getting gas in Umatilla OR, adding about 2.5 gallons to fill it up, parked the bike for about an hour to have lunch. It was around 95F. For the next 120 miles, when I tried to open the gas over about 1/3 throttle under load it would run rough and not rev higher. At idle or low speeds it ran totally fine. I turned the bike on/off a couple of times and removed/replaced the fuel cap once. Nothing helped.

Going into a head wind it got worse and I couldn't pass anybody. At one point I slowed down to about 30mph due to traffic and when I tried to speed back up it ran rough and stalled. I restarted and got it going again and back up to road speed which was about 65mph, but still couldn't get it to rev past about 5k in 6th.

I got gas again in Bingen WA, 120 miles later, putting in about 3 gallons to fill it up. From then until I got home it ran completely fine. The change was immediate after I left the gas station.

Fuel filter seems an obvious potential culprit, but it's weird the problem went away. What else should I check?

Thanks!

Stephen
2011 KTM 990 SMT
2007 Suzuki GSXR750 (Track toy)
2004 BMW R1150RT (Keeps the wife happy)

Andy J
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Re: Power loss under load

Post by Andy J » Wed Jul 27, 2016 4:51 pm

I would suggest a bad batch of fuel. Once you refilled it was diluted enough to cure it.
Could have had water in with it if the storage tank was old and corroded or it could have even had a small amount if diesil mixed in with it if the truck transporting the fuel to the gas station hadnt cleaned its tanks correctly between loads.
Could also have had solids in suspension which would have blocked the fuel filter but its unlikely that a fresh tank of gas would solve it so im going with a batch of poor quality fuel.
Just run another few gallons through and if the issue doesnt return then theres your answer!

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seh750
250cc
250cc
Posts: 65
Joined: Thu Apr 07, 2011 10:57 pm
Country: USA
City: Beaverton, OR
Year: 2011
Colour: White
Location: Oregon, USA
Contact:

Re: Power loss under load

Post by seh750 » Thu Jul 28, 2016 5:54 am

Bad fuel is certainly a convenient explanation. I'll have to take it for a few more test rides and see if the problem stays gone.

Thanks for the input.
2011 KTM 990 SMT
2007 Suzuki GSXR750 (Track toy)
2004 BMW R1150RT (Keeps the wife happy)

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