Bad stuttering at higher rpms

[agentbad]

I took my bike on the highway for the first time and as I was getting into the higher rpms I started to get some really bad stuttering around 6000 to 7000rpm. I have been running seafoam through the carbs but it doesn't seem to be doing much. I have also noticed when I start the bike when I try to give it throttle right away it will die. I can give it a little throttle and it will give out this sound like air is leaking with a sputter on the right side. Does this sound like a carb issue or something else?

[FvnnyL3tt3r1ng]

Originally Posted by agentbad

I took my bike on the highway for the first time and as I was getting into the higher rpms I started to get some really bad stuttering around 6000 to 7000rpm. I have been running seafoam through the carbs but it doesn't seem to be doing much. I have also noticed when I start the bike when I try to give it throttle right away it will die. I can give it a little throttle and it will give out this sound like air is leaking with a sputter on the right side. Does this sound like a carb issue or something else?

You probably need to clean the carbs. Replace the fuel filter while you're at it. How is your idle after the bike warms up? What rpm does it idle at?

After you've warmed up the bike try to lower the rpms to the lowest rpm you can and let us know what you get.

[Live2ride]

Does the bike have a jet kit or shimmed Carb needles? Any mods to the air box? By stuttering do you mean it will not go past 6-7k rpm, or it only stutters during those rpm's but continues running above that rpm?

[agentbad]

It will rev past that but it stutters/jerks when I try to keep a constant cruising speed and it's really distracting. As far as I know it's stock. The original owner said the carbs had been cleaned but they must have done a crap job. It only has 5600 miles or so it's not quite time for a valve check.

You know what I bet when the last owner installed the pod filter he didn't rejet the carbs. That would make sense why it's running bad. I didn't notice it until just now.

[slickt0mmy]

Mine has the exact same problem. Anything from 6k-8k rpm, especially in 5th gear, stutters really badly. I just finished adjusting my valves and syncing my carbs, so I know that isn't the culprit. It's driving me crazy!

[agentbad]

I am pretty sure the previous owner screwed the carb up when he cleaned it last and he also didn't rejet after adding a K&N pod filter. Fortunately that will make getting the carbs off way easier without the air box getting in the way. Mine is running to lean now because of the K&N filter and possibly a bad gasket on one side.

Originally Posted by slickt0mmy

Mine has the exact same problem. Anything from 6k-8k rpm, especially in 5th gear, stutters really badly. I just finished adjusting my valves and syncing my carbs, so I know that isn't the culprit. It's driving me crazy!

You sure all the jets were clean?

[slickt0mmy]

Originally Posted by agentbad

I am pretty sure the previous owner screwed the carb up when he cleaned it last and he also didn't rejet after adding a K&N pod filter. Fortunately that will make getting the carbs off way easier without the air box getting in the way. Mine is running to lean now because of the K&N filter and possibly a bad gasket on one side.



You sure all the jets were clean?

That may well be it. I used the two-bottle method to sync them, so I didn't dig too far into it but now I'm thinking I should have just gone ahead and taken the carbs off while I was at it and given them a good cleaning.

Would shimming the needles help at all?

[agentbad]

Originally Posted by slickt0mmy

That may well be it. I used the two-bottle method to sync them, so I didn't dig too far into it but now I'm thinking I should have just gone ahead and taken the carbs off while I was at it and given them a good cleaning.

Would shimming the needles help at all?

I know for the pod filters you are supposed to but not sure about stock.

[Motofool]

Before attempting surgery, check if you have enough fuel supply (2 cc per second) to the carbs.

If so, try using the choke when the problem appears and note any difference.

[alex.s]

inspect the air cleaner.

edit: oh i see pod filters. check jetting. get rid of the pods.

[agentbad]

Originally Posted by alex.s

inspect the air cleaner.

edit: oh i see pod filters. check jetting. get rid of the pods.

I would put the old air box back in but the guy got rid of it. I agree with rejetting I am reading the ninja faq and it says something between 108, 110, 112 for the main jet. You need one for both carbs correct? Also should I shim the needles as well?

[alex.s]

2 carbs means 2 sets of each jet. you will need to adjust the pilot jets also. jetsrus.com

[Motofool]

Originally Posted by alex.s

2 carbs means 2 sets of each jet. you will need to adjust the pilot jets also. jetsrus.com

Could he partially block the air intake by covering part of the pods?

Originally Posted by agentbad

I took my bike on the highway for the first time and...........

At least temporarily, he could limit the excess of air in the mix and finally start riding that bike.

[alex.s]

its definitely a hack. but it would temporarily get it closer. but correct jetting with a real air cleaner (that isn't wrapped in tape that can come off/shift/do something different) should be a priority


you should be able to buy a used airbox for cheap

[agentbad]

Originally Posted by Motofool

Before attempting surgery, check if you have enough fuel supply (2 cc per second) to the carbs.

If so, try using the choke when the problem appears and note any difference.

How would I check the amount of fuel supply to the carbs? That's a good idea about the choke maybe that will help it not run so lean. If I were to block part of the filter what material would I use? I have duck tape and a old rag ready for Macgyvering.

Originally Posted by alex.s

its definitely a hack. but it would temporarily get it closer. but correct jetting with a real air cleaner (that isn't wrapped in tape that can come off/shift/do something different) should be a priority


you should be able to buy a used airbox for cheap

I'd like to keep the pod filter just because it makes maintenance a lot easier by freeing up space and the little boost in hp seems worth it.

[Motofool]

Originally Posted by agentbad

How would I check the amount of fuel supply to the carbs? That's a good idea about the choke maybe that will help it not run so lean.

Just disconnect the vaccum hose from the petcock and connect another clean hose from which you can suck with your mouth.

Then disconnect the hose that feeds the carbs and place the end inside a glass container of known volume.

Open the petcock and apply vacuum to it and record the time that it takes to fill the container or to reach any pre-made mark.

Don't know how to block the filters; it was just an idea to test if the mix is too lean or if you have other problems.

You may find additional ideas in this concurrent thread:

http://www.ninjette.org/forums/showthread.php?t=137183

[agentbad]

Which jet kit should I get? I am going to have a local shop install it since I am not experienced with carbs yet.

[FvnnyL3tt3r1ng]

I run factory pro jets and I think they're pretty awesome. Best money I've spent on the ninja by far.

It's pretty important you get the jetting right because this stuttering is because your running too lean in the mid range. If you're on a tight budget I would just buy the washers and shim the needles. Ideally you want to buy the jet kit because it's pretty touchy and hard to tune optimally without the right set of main jets.

If you're mid range is suffering (which in your case it is) then your high range is gonna suffer just as well.

Just as an fyi I run 110 main jets and the needles in clip position number 2 w/ one washer underneath. You can check out the "How to pod" thread to see how I tuned mine.

[agentbad]

Thanks for the advice. The Ninja faq wiki suggests factory pro over dyno as well. I am going to take it in this week and get it worked on at one of the local shops. Whats a good online store that sells the factory pro kit for my bike '05 Ninja 250F. I see they have it on there website for around $100 after shipping but I have seen it for $80. Think the model is CRB-K13-3.0.

edit: Going the jetsrus route.