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Old 12-12-2010, 10:25 AM   #1
blackj
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Default Power Loss at 7000rpm follow by a backfire

On a rider last weekend on my 2002 SV650S the bike started loosing power when I tried to maintain a speed just of 80 mph or 7000rpm. It would accelerate up to it fine. But just over 80mph there was loss of power with a drop in rpm. This happend until about 6500rpm when the bike would backfire/pop and then start to accelerate again.

I'm not sure if the bacfire is part of the problem or is a result of the power loss resulting in unburn gas getting expelled into the exhaust system.

Has anybody encountered a similar problem before? and has a fix?

Thanks
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Old 12-12-2010, 11:23 AM   #2
MOKE1K
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There is something your leaving out. Perhaps it's been sitting?
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Old 12-13-2010, 05:34 AM   #3
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That bike has carbs; they may be seriously out of sync and/or in need of cleaning and adjustment. When was the last time the bike was tuned up?

Or: did somebody change the stock exhaust for a performance system? If so, the loss of backpressure could cause your symptoms, especially if there was not a corresponding re-jet on the carbs done with the exhaust change.
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Old 12-13-2010, 07:54 AM   #4
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The bike hasn't been sitting, I pretty much ride to work everyday. Its just a short 9 mile trip so I don't get into that speed range.

The bike is all stock but maybe it could do with a tune up or the carbs being cleaned. I bought the bike nearly two years ago with 22k miles on it just after a service and since then I had it serviced after 3k miles but I didn't have the carb cleaned or adjusted.
Is there anything I could look for that might indicate that this could be the problem?

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Old 12-13-2010, 08:14 AM   #5
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You could pull the sparking plugs and see if they're wet, black, etc. Aside from that, tune up need is symptomatic.

Maybe you just got a bad batch of gasoline, or high-ethanol gas.
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Old 12-13-2010, 09:45 AM   #6
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Looks like you blew a seal.....
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Old 12-13-2010, 10:12 AM   #7
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That would be a little abnormal to have blown a seal this early, but not that it couldn't happen. I think it's from lack of use even though he admits he rides it everyday, you and I both know it needs a little flogging once in awhile. They aren't meant to be babied.
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Old 12-13-2010, 10:12 AM   #8
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Check the inside of the tank for rust, or possibly bad smelling fuel. Pop the tank and inspect the throttle linkage aswell. Then I'd pull the plugs. My guess is the rear cylinder plug possibly. Your not leaving the choke
open are you?
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Old 12-13-2010, 11:09 AM   #9
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I don't think its bad gas as it happened once during the summer, I was on the I-10 in Arizona and it was 114F heat . But at around exactly the same speed.

I might not be running it too hard on the daily commute but I do have a couple of freeway miles so it is getting up to 70mph "without issue" daily.
I replaced the spark plugs about 1000miles ago.

I'm not leaving the choke open, although it wouldn't be past something I could do.
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Old 07-20-2011, 03:49 PM   #10
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Sounds like fuel is not getting to the carbs. Clean everything. you will need a blow-gun on low pressure.

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