Idleing too high and slow acceleration problem

[Arkangel1200]

So I have a 2008 ninja 250 (duh) but my bike has almost 50,000 miles on it. It has a K&N air intake, a two brothers carbon slip on. The bike seems to be idling weird. I set the idle after warm-up to about 1250rpms. But when riding it idles up above 3,000-4,000. Only sometimes though. Sometimes it doesn't. I have the air filter in and the slip on installed but I don't believe it's tuned with them on. So is that the issue. And will this problem of it not being tuned make me get bad gas mileage? I drove 1,380 miles straight from california to texas. And my average gas mileage was 45mpg. Which is pretty bad for a 250 if you ask me. That's cruizing at around 80-85mph. With being all freeway riding I was expecting at least 65mpg.

[csmith12]

Welcome Zack!

Actually... in nearly stock form, that don't sound too far off mgp wise. 45mph @80mph is near the top end of the bike's abilities, that is NOT where the mpg shines. Your gunna have to slow down a bit or do some mods to see higher mpg @ higher mph.

As far as your high idle and such. My guess is..
The bike is slightly lean in stock form and that was made worse by the filter and slip on. It aint much, but it can be enough. Pull a plug and see what it looks like. Has it been sitting for the off season? Since I would suspect your gunna be in the carbs doing some jetting/shimming anyway, might as well give em a good cleaning while you're there.

[Arkangel1200]

Originally Posted by csmith12

Welcome Zack!

Actually... in nearly stock form, that don't sound too far off mgp wise. 45mph @80mph is near the top end of the bike's abilities, that is NOT where the mpg shines. Your gunna have to slow down a bit or do some mods to see higher mpg @ higher mph.

As far as your high idle and such. My guess is..
The bike is slightly lean in stock form and that was made worse by the filter and slip on. It aint much, but it can be enough. Pull a plug and see what it looks like. Has it been sitting for the off season? Since I would suspect your gunna be in the carbs doing some jetting/shimming anyway, might as well give em a good cleaning while you're there.

So I'm riding back to California tomorrow. What is the best speed for the best gas mileage? 65mph? And also, I replaced the spark plugs right before I left and it seemed like one looked a bit lean but nothing crazy. But I should tune it anyhow?