Need help troubleshooting

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2009 ninja starts to bog at take off sounds very muffled and will pick up slowly only up to 55mph at times after riding for a while it will start to sputter get higher pitched and pick up speed and ride normal last time I rode it ran crappy and I could smell gas and had to keep on the throttle to keep it on don't want to just throw away my money trying to fix it any idea what it could be maybe carb problem got 41000 miles on it

[Triple Jim]

As a very wild guess, I'd say one cylinder is not firing most of the time. Since it starts working after a while, my guess is that it's carburetor related, but it could be ignition related, and something as simple as a fouled plug. (which could have become fouled because of a carburetor problem)

If you're not firing on one cylinder, its head pipe will stay cold, or at least be less hot than the one that is firing.

[jkv45]

What TJ said ^, and what does the inside of the tank look like?

Have you checked the condition of the air filter lately?

There could be debris from the tank that has made its way down to the carbs and is holding a float up (dumping extra gas in and maybe out the overflow) or the fuel pick-up screen or filter (if there is one on that Gen) may be getting partially plugged.

With that many miles there could be a number of things that need attention, like the plugs if they haven't been changed recently.

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Took out air filter and spayed carb cleaner inside while bike was on a few times and it started to run just fine afterwards any clue why

[highvoltj]

Sounds to me like you have a fuel delivery issue if it ran better when you sprayed carb cleaner into intake...maybe clogged main-jet. However, if it were me, as your bike has 41k on the motor, I would go the distance and start with checking valve clearance, remove carbs and clean, (check jets for clogs) visual carb plate sync while carbs are off and also change plugs ( I use iridiums just cuz it's a PITA to change them) and if that doesn't resolve then go to electronics...bad coil or boot and wire? Sadly there is probably no "quick fix" to this issue.