small stutter

[amatthews361]

i have an 07 250r. i usually ride my bike at least a couple times a week, but i went to ride the other day and it starts to stutter when i maintain 6500-7500 rpm. its perfectly fine when accelerating and above 8k rpm. I figured i would just clean the carbs even tho the shouldnt need it since i just did a few months ago, but i did and they are spotless. couldnt even find a single deposit anywhere. the plugs are brand new ngk and the bike has 10k miles. idk what else it could be. any ideas?

[Alex]

Dirty air filter and bad gas are two possibilities.

[amatthews361]

i always get my gas from the same place and its 93 octane and non-ethanol, also just cleaned the airfilter.

[DaBlue1]

Any mods to the bike?
Have you checked the Troubleshooting Guide?

[amatthews361]

nope. its bone stock

[Motofool]

Originally Posted by amatthews361

...........idk what else it could be. any ideas?

I don't know either.

Welcome to Ninjette.org, Andrew !!!

[amatthews361]

thanks for the welcome. but this issue has me stumped and ive been working on gas engines for the past 5 years. thats why im here trying to get more ideas from everyone.

[Motofool]

Originally Posted by amatthews361

thanks for the welcome. but this issue has me stumped and ive been working on gas engines for the past 5 years. thats why im here trying to get more ideas from everyone.

If the carburetors, air intake and fuel supply are OK, I would check for electrical connections and cables of both coils and sparks that could resonate at those rpm's and create some temporary false contact.

I would even disconnect the ignition one side at a time and observe if the symptom is asymmetrical.

The origin of problems like the one puzzling you are very hard to determine most of times.

[amatthews361]

i was wondering if it could possibly be the coil(s). but ive just never had a coil work great at certain rpm ranges and not others. either they work all the time or dont from my experience. other thing i thought about is could it possibly be valves are loose?

[jkv45]

Had the tank been sitting with a low level of fuel in it? If so, you could have enough condensation to cause problems.

You could drain the float bowls and see if there's any water. You may need to remove the tank and dump it to get all of the water out.

If you can get lower octane gas without ethanol, use it. 87 without ethanol will give you the best power and mileage. If you can't get 87 without ethanol then I would use the next highest grade available without ethanol.

[amatthews361]

the only gas i can get that is non ethanol is 93 and no the bike is driven just about every day. only had it 6 months and already put nearly 7k miles on it =). also i checked the gas and it is good, water in my gas was the first thing i thought about bc it happens alot here in the south with all of the humidity.

[Motofool]

Originally Posted by amatthews361

i was wondering if it could possibly be the coil(s). but ive just never had a coil work great at certain rpm ranges and not others. either they work all the time or dont from my experience. other thing i thought about is could it possibly be valves are loose?

My experience about coils coincides with yours.

Valves regulate engine's breathing, which difficulty becomes evident either at idle (unstable rpm's) or WOT (lack of power).

My experience would say that your middle range symptom could only be related to valves if one or more springs are somehow weak and resonates at that range of rpm's.

I have a 2007 with 25K miles, and valves and springs are still in very good condition.

[amatthews361]

im just throwing out ideas. i really dont see where it would be valves especially since it just started doing this in the past few days and like i said, i ride the bike pretty much every day. my experience just keeps telling me that its carb issues. but i just didnt see anything wrong and i did a carb soak anyway since i had them off and they are a pain to get off with the stock airbox in the way.

[jkv45]

Originally Posted by amatthews361

the only gas i can get that is non ethanol is 93 and no the bike is driven just about every day. only had it 6 months and already put nearly 7k miles on it =). also i checked the gas and it is good, water in my gas was the first thing i thought about bc it happens alot here in the south with all of the humidity.

If the carbs look good I would still drain the tank and refill with fresh gas from another location before digging-in too deep.

What do the plugs look like? Have you shimmed the needles or adjusted the idle mixture screws?

I would also run the 93 if it's the only gas you can get without ethanol (I hate ethanol), but if it's not a fast-mover at the station it may have been sitting in the storage tank for a while. Find the busiest station you can are get some fresh.

[DaBlue1]

Originally Posted by amatthews361

the only gas i can get that is non ethanol is 93 and no the bike is driven just about every day. only had it 6 months

Originally Posted by amatthews361

...it just started doing this in the past few days

What part of SC are you in?
I probably wouldn't worry about it too much. Here in the south we've had a nice few 80 degree days and also a switch from winter gas to summer gas in most places. We are also going to see a switch again to some low temps so small engine performance may be a tad bit sluggish. BTW how old is your air filter? It can be clean, but still be old, compressed and restrictive.

Ever considered shimming the needles and doing the airbox mod?

Shimming can help smooth out the range where you have the stutter.

[ninjamunky85]

Drain the gas tank, refill with 87 octane.

[jkv45]

Originally Posted by ninjamunky85

Drain the gas tank, refill with 87 octane.

Usually, yes, but where there's a choice of ethanol-free I always take it - even if it's higher than required octane. He siad 93 is the only grade available in his area without ethanol - so that's the way to go IMO.

In a perfect world you'll get your best performance and mileage from the lowest octane fuel that doesn't detonate (87 for the Ninja), BUT, when there's ethanol added all bets are off.

Ethanol causes all sorts of problems (corrosion, damage of gaskets and seals, rust, lean mixtures, etc...etc...) and I'll avoid it whenever possible.

[MaxxVE]

I have a stock 2006 that does the exact same thing. Like you I haven't been able to figure it out. I'll be shimming the needles this weekend like someone recommended earlier in the thread. I'll try to post back with this results.

[ninjamunky85]

Originally Posted by jkv45

Usually, yes, but where there's a choice of ethanol-free I always take it - even if it's higher than required octane. He siad 93 is the only grade available in his area without ethanol - so that's the way to go IMO.

In a perfect world you'll get your best performance and mileage from the lowest octane fuel that doesn't detonate (87 for the Ninja), BUT, when there's ethanol added all bets are off.

Ethanol causes all sorts of problems (corrosion, damage of gaskets and seals, rust, lean mixtures, etc...etc...) and I'll avoid it whenever possible.

Thing is that not a lot of people buy premium gas so its more likely to sit in the underground tanks at the gas station and collect water.

I live in Ohio. We've had E10 gas for years and I've never had any problems.

[Ninjinsky]

1/
7k is right at the point where the power takes off and all the resonances chime in. Since you can't have your cake and eat it there might be a small 'dissonance' zone at around 6k. I notice that mine feels uncomfortable at that rpm, a bit like an RD stroker just before it gets on the power band.

2/ In a high gear what happens as you whack the throttle or just caress it? ie pulling the needle to the top or keeping it in the mid position which are 2 radicaly different carburations in the same condidtions

3/ Just check that the ht leads are firm in the coils, I have had one come loose and cause much erratic wierdness.

[amatthews361]

when i go WOT its perfectly fine, but if i ease the throttle or try to maintain around 7k rpm it just stutters and doesnt have smooth power at all.

[Ninjinsky]

Hmm, I'd check the diaphragms for slight twist (and small tears if so) and check the slides for stick free movement. The flat slide element is more susceptible to a bit of twist-stick than a round one would be