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1MNeary · June 24th, 2019, 03:40 PM

I have an 08 ninja 250 as the title states, and it recently developed a miss at about 8-9000 rpm. It runs perfect up to 8000rpm and when I take off it will hit redline no issue in first gear, you can barely detect a miss in second, and from third on you get a miss at 8000rpm and it doesn’t want to rev any higher. If you cruise in sixth it starts stumbling intermittently at about 7000 and it gets more frequent as rpm increases until about 8500 where it bogs and won’t go any faster.

Mods: slip on muffler off a big bike, snorkel removed, jet kit(unknown jet sizes), emission delete(done correctly).

Gearing is currently stock

I bought the bike with all mods except emission delete with 8500 miles on it less than a month ago. It ran pretty good for 100 miles but felt a little rough(6000rpm stumble, choppy idle). I did an oil and filter change, put fresh cr8e plugs in it(didn’t adjust gap), ran a fuel system cleaner through it, and did a clean and re oil on the factory filter. The bike ran PERFECT for 700 miles, lots of spirited riding, several 100 mile highway trips at 80mph, then the other day it starts doing the problem I described.

I pulled the tank off and performed the mod where you enlarge 3 holes on the gas cap( I live in FL my bike was beeping constantly), drained the tank, verified no rust or foreign debris, cleaned the filter(it was clean), and checked all hoses on the tank and carb. I also verified the plug wires were snug while I had it apart. I put 1/2 gallon of fresh 93 octane in the bike and took it for a ride, the issue persists.

When riding the bike slowly into high rpm the stumble is felt less but still exists, and still will not go any faster in 5th and 6th. When the choke is applied full the bike backfires constantly and runs worse, at 1/2 choke it does the same thing but runs pretty much the same until you let off the gas, then it backfires. At 1/4 choke it runs no different and also backfires after letting off at wide open throttle.

I have searched all day and found lots of people with this issue but not allot of clear answers to what the fix is. Anybody had this issue and resolved it?

June 24th, 2019, 03:40 PM	#1
1MNeary ninjette.org newbie Name: Matthew Location: Lakeland FL Join Date: Jun 2019 Motorcycle(s): 09 Ninja 250 19 grom Posts: 4	08 250R miss under load at high RPM I have an 08 ninja 250 as the title states, and it recently developed a miss at about 8-9000 rpm. It runs perfect up to 8000rpm and when I take off it will hit redline no issue in first gear, you can barely detect a miss in second, and from third on you get a miss at 8000rpm and it doesn’t want to rev any higher. If you cruise in sixth it starts stumbling intermittently at about 7000 and it gets more frequent as rpm increases until about 8500 where it bogs and won’t go any faster. Mods: slip on muffler off a big bike, snorkel removed, jet kit(unknown jet sizes), emission delete(done correctly). Gearing is currently stock I bought the bike with all mods except emission delete with 8500 miles on it less than a month ago. It ran pretty good for 100 miles but felt a little rough(6000rpm stumble, choppy idle). I did an oil and filter change, put fresh cr8e plugs in it(didn’t adjust gap), ran a fuel system cleaner through it, and did a clean and re oil on the factory filter. The bike ran PERFECT for 700 miles, lots of spirited riding, several 100 mile highway trips at 80mph, then the other day it starts doing the problem I described. I pulled the tank off and performed the mod where you enlarge 3 holes on the gas cap( I live in FL my bike was beeping constantly), drained the tank, verified no rust or foreign debris, cleaned the filter(it was clean), and checked all hoses on the tank and carb. I also verified the plug wires were snug while I had it apart. I put 1/2 gallon of fresh 93 octane in the bike and took it for a ride, the issue persists. When riding the bike slowly into high rpm the stumble is felt less but still exists, and still will not go any faster in 5th and 6th. When the choke is applied full the bike backfires constantly and runs worse, at 1/2 choke it does the same thing but runs pretty much the same until you let off the gas, then it backfires. At 1/4 choke it runs no different and also backfires after letting off at wide open throttle. I have searched all day and found lots of people with this issue but not allot of clear answers to what the fix is. Anybody had this issue and resolved it?