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Discussion Starter #1
Hi, recently bought an sv650 that needed some love and a good clean. It wouldn't start before i bought it but new plugs fixed it and it ran great. The clutch is slipping but the bike revved fine and went strong. Now however the bike will not rev past 6k, it's like the redline has been lowered. The bike runs fine under 6k.

I've cleaned the carbs again today but it will still not rev, one jet was clogged but the rest were fine
The tank is up and airbox off
Good fuel
New plugs
Both exhausts seem to be at the same temperature (measured)

Could it be some vacuum lines? The carbs not getting enough fuel from the tank? It worked perfectly fine one day and the next it just stopped. Without being ridden.
 

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Vacuum lines are always suspect, but I would flush out the tank next. If one jet clogged after it was running well it could just be a continuing supply of crud from an old tank.
 

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How old is the gas? Any chance it got water in it?

Gas with ethanol can go bad quickly and hold a lot of water.

I've had old/bad gas do what you described.

Does it sputter or surge as it flattens out, or just stop revving?

Will it accelerate smoothly at WOT at lower RPMs?
 

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Discussion Starter #4

Haven't tried accelerating WOT with it but close and it was fine. The response under 6k is fine. Idles fine but sometimes cuts out.

The video is with fresh gas fed straight into newly cleaned carbs. It backfires sometimes and i saw that the front plug hat isn't flush with the valve cover like the rear plug hat is. I don't think i properly screwed in the front spark plug, could this cause these symptoms?
 

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Haven't tried accelerating WOT with it but close and it was fine. The response under 6k is fine. Idles fine but sometimes cuts out.

The video is with fresh gas fed straight into newly cleaned carbs. It backfires sometimes and i saw that the front plug hat isn't flush with the valve cover like the rear plug hat is. I don't think i properly screwed in the front spark plug, could this cause these symptoms?
I would expect a loose plug would cause problems.

Check your battery voltage. It should be over 12.7V before cranking and over 10 V during cranking.

Does it sputter and only hold 6000 RPMs wide open? If so, I'd say something in the carbs isn't right. The video ended rather abruptly.
 

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Hi everyone, I'd like to chime in to get help with what seems to be the exact same problem. I've bought the 01 SV and it had this problem from start, a few days ago the plugs were changed, carbs cleaned and synced, oil and filters changed... Standard service stuff, but the problem is still there.
Not much I can contribute to thread with my knowledge other than I noticed that back cylinder gets a bit hotter sooner than the front one. And the previous owner changed the battery a few months ago, so there might be some electrical problems that cause this.
 

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Discussion Starter #8
It has been solved, running it without the filter makes it run like shit. Never had such a dramatic difference with any of my other bikes but that was the problem this time. Put the filter back on and now it runs beautifully.

Thanks for everyones advice!
 

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Good you got it figured out.

Goes to show you really need everything assembled completely and operating under normal riding conditions to diagnose a problem accurately.
 

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It has been solved, running it without the filter makes it run like shit. Never had such a dramatic difference with any of my other bikes but that was the problem this time. Put the filter back on and now it runs beautifully.

Thanks for everyones advice!
Glad you found the problem. Constant Velocity carbs are a semi-sealed system and rely on the correct partial vacuum. Removing the Air-Filter interferes with this as do any Air-Leaks onto the system.The Air-Filter system can be changed for things like pods but then other tweaks/mods have to be applied to compensate.

:)
 
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