2009 ninja 250 running rough

[AZninja]

Hey guys, I just got a 2009 Ninja 250 with 13k miles. It runs perfectly during the day. At night though, it has trouble staying alive after i start it. It runs really rough and sounds horrible. It take 10 minutes or so to warm up enough and even then it will still die sometimes. This only happens at night as well.

Is this an issue with the gas or carbs? I'm running 91 octane through it now. Any help would be greatly appreciated.

The previous owner had an aftermarket exhaust(mgp growler) put on and told me he re-jetted for it.

[Jiggles]

Run 87. Has the bike sat without running for over 2 weeks? If so try running some seafoam through it. To me though I think your jetting needs to be changed. Sounds like you have a lean issue?

[AZninja]

I put about a 1/4 can of sea foam when i filled up last time to see if that would help. He said it sat for about 3 weeks but he rode it to the store about once a week. Next time I fill up should I put more seafoam in do you think? Should I buy a whole new Rejet kit like dynojet brand? Sorry i'm new to this stuff.

[Jiggles]

You can try the seafoam if you want but make sure you use 87 octane. 91 has extra crap that isn't good for the bike and will generally make it run not as well, it could be contributing to your problem.

I would guess that either your carbs need to be cleaned or if they are clean then you need to rejet. Either way you need to crack that bad boy open. Are you planning on ever doing some exhaust or intake mods to squeeze some more ponies out of the 250? If so then get a whole dynojet kit, if not you can get away with maybe one size up main jets and 2 shims under the needles. Check the DIY in the tech section to understand what the hell I'm talking about

[AZninja]

Yeah, its starting to sound like a jet issue. It also backfires/Afterfires after I let off the gas at higher rpms and upon engine braking/downshifting. How much does it usually cost to rejet? Like $150 for parts/labor?

[Jiggles]

Originally Posted by AZninja

Yeah, its starting to sound like a jet issue. It also backfires/Afterfires after I let off the gas at higher rpms and upon engine braking/downshifting. How much does it usually cost to rejet? Like $150 for parts/labor?

Do you have a full exhaust or just a slip on? If it's just a slip on you could get away with just buying a one size bigger main jet $10 and some washers to shim the needles $0.25. Then take a few hours to take your bike apart and install the parts. Alternatively you can pay someone else $200 to do something rather straightforward and simple for you.