8k rpm or better bike stumbles where to begin

[RockyCapone]

Now that I'm learning how to drive better I've discovered that the bike stumbles at 8500 rpm under full throttle. Ive tried to unthrottle and get back in and seems to help but no big deal. The bike has a single exhaust on it by Kerker and other than that i believe its stock. Ive redone the valves, new correct NGK plugs, oil and filter is new, the tank vent is not plugged, set the idle mixture screws to 2 turns out and air filter is clean. Unsure of history because I bought bike off of a guy selling it for his son who move out of state, the alltitude there is about 500. From idle to 8k rpms it feels perfectly fine but like I said if I full throttle from a stop it always breaks up at 8. I dont think shiming the needle would do I thing because thats for low rpm problems correct? As far as choke my lever on the bar moves half way and sticks is that right? Also choke don't do anything to my idle speed. What size main jet are other running at 3000 altitude? I will this weekend check my carb syn and float heights but curious what others have done to jetting and sizes with aftermarket exhaust-as long as I'm in there might as well document everything.

[csmith12]

If your bike has a full exhaust without proper jetting, it will do that. Was a jet kit installed along with the single sided exhaust? I would start there.

[RockyCapone]

Originally Posted by csmith12

If your bike has a full exhaust without proper jetting, it will do that. Was a jet kit installed along with the single sided exhaust? I would start there.

That's my thought. Im a noob to bikes so my biggest question is stock jetting is what? Where to go and find correct jetting number size or at least the ballpark area.

[lgk]

You can look here and see if any of the data matches.

http://www.ninjette.org/forums/showt...TTING+DATABASE

[Jiggles]

I have that too, granted my jetting is way off but I think with aftermarket exhausts and jets its bound to stumble there. The BRT ignition or w/e is supposed to fix that

[alex.s]

Originally Posted by Jiggles

I have that too, granted my jetting is way off but I think with aftermarket exhausts and jets its bound to stumble there. The BRT ignition or w/e is supposed to fix that

drop your needle and it will fix that rich spot

[RockyCapone]

Well for a start I'm going this route, supposed to rain here in Arizona tomorrow and Thrursday so it'll give me some time, http://www.ninjette.org/forums/showt...jets+carb+bike
What pisses me off is guy said carbs just redone by local guy-maybe maybe not-I'll know when I open it up and look at it. So I guess my baseline will be this and even though it wont be no full throttle run in top gear I will check the plugs and so how white they are or black. Looks like my jetting area should be around 108 to 110 based on others here from a link someone else just put up, probably more 108 or even smaller because of my alltitude. For me I can drive 30 minutes and be at sea level, 30 again back home at 3000, or 30 the other way and be at 5500, was a bitch with the dirtbikes.
So glad I bought this bike vs the Honda-the info here is super and detailed. but the search engine here really, really sucks.

[choneofakind]

Originally Posted by RockyCapone

but the search engine here really, really sucks.

use google. www.ninjette.org: search words



Sounds like you need new mains. FYI, stock main jets are 105. Going up from there, test the 108's and 110's. Your elevation changes kind suck! that would be really annoying.

[RockyCapone]

Removed carbs yesterday and what I found was lots of crap and typical wanna be mechanic work. So here's what I found along with some questions for some of you that know. First I knew I had a problem with the fuel enrichment "choke" but wasnt sure but when I pulled it apart I found the right side carbs choke was frozen in the middle and the other working just fine. Second lots and lots of crud in the bowls-from what I've seen shouldnt I have a very small screen to the inlet line at the black elbow? 3rd and this has to be wrong the main jets I cant the sizes but one jet sits deeper than the other-gotta be wrong right? LOL. The butterflies not perfectly the same. I'm sure I'll remember more but I'm uploading pics right now to show you guys what I mean. I found simple carb kits on Ebay for like 16 each and a jet kit for like roughly 50. Ohh yea do I have to seperate the carbs to soak in a gallon drum of carb cleaner or do you never seperate those guys?

[RockyCapone]

test pics

[RockyCapone]

This hose I lost track of somehow and it fell out of the bike, should this be capped of like this or is the jerry rigged?

[Fappy]

You're not really alone...Mine has a hesitation between 8-9k rpms too. I've just decided that it's a result of my exhaust having some holes drilled into it from the previous owner, and am just living with it.

That dyno chart from Jiggles seems to reflect its natural tendency to have some slop right at that RPM range.

[RockyCapone]

Originally Posted by Fappy

You're not really alone...Mine has a hesitation between 8-9k rpms too. I've just decided that it's a result of my exhaust having some holes drilled into it from the previous owner, and am just living with it.

That dyno chart from Jiggles seems to reflect its natural tendency to have some slop right at that RPM range.

Ya but mines the direct result of horsecrap work. Whats worse is the owner told me the carsb just rebuilt-yea right. If I would of left it that way I would of melted down one cylinder and maybe washed the rings down on the other side. At least I'm learning my machine inside and out. Besides this is my learner bike for driving and maintenance so when I step up to my 08-12 250 next year I wont be lost.

[02337]

More than likely a vaccuum hose, why it's capped is a little shadey. If you google ninja 250 carb vacuum hoses there's a nice diagram that shows where each hose goes.

[choneofakind]

There's a little capped hose that comes off the bottom of the airbox. Should be about a foot long, give or take a bit. Check your airbox before you freak out about missing a hose from your carbs.

[RockyCapone]

so far by soaking carb the choke has released and works fine. The housing is all clean and blown out. Turns out the squid/dick before did have 2 different jets a 106 and 108 and both different heights. The needles I understand originally made out of brass or copper and these are steel so rather than by a jet kit I'll just rebuy new 108 jets. Air bleeds are 38, going research those to see if I'm in the ballpark for those also.

[choneofakind]

The jets are brass.

The stock needles are Aluminum. You sure yours are steel? Try a magnet.

here's some info on needles: http://faq.ninja250.org/wiki/Ninja_2...le_Information

[RockyCapone]

Originally Posted by choneofakind

The jets are brass.

The stock needles are Aluminum. You sure yours are steel? Try a magnet.

here's some info on needles: http://faq.ninja250.org/wiki/Ninja_2...le_Information

From the link:
The Ninja 250's stock carburetor is a Keihin CVK30.

The stock needle is marked N16I at the top, and is Kawasaki part number 16009-1461. It's made of brass.
Mine are aluminum.

[choneofakind]

Maybe the oem needles are brass then? But they seem too light to me to be brass. How are you sure that yours are Aluminum?

Do your needles have e-clips and slots in them to adjust the height of the e-clips? If not, they're the stock needles.

This is a stock needle for a new-gen, right next to a jet-kit needle for a new-gen:

Which one of these needles do your needles look most like?

[RockyCapone]

Originally Posted by choneofakind

Maybe the oem needles are brass then? But they seem too light to me to be brass. How are you sure that yours are Aluminum?

Do your needles have e-clips and slots in them to adjust the height of the e-clips? If not, they're the stock needles.

This is a stock needle for a new-gen, right next to a jet-kit needle for a new-gen:

Which one of these needles do your needles look most like?

Mine looks just like the left one with a washer under it. Interesting. I'll get pic tonight, all I brought to work today was housing and bowls.

[choneofakind]

That's likely the stock needle. Check just under the top of the needle to see if it has the N16I markings.

[RockyCapone]

Results after everyones help and all the info here is awesome. Whats unreal and i did coppy Choneofakinds setup it was right on from the start even rpms only 200 off. I thought originally the power i had was expected now its a whole new animal 14k rpms thru 3 gears at that point had to slow down. So for my bike it liked 108s/38s/3 washers/ and 2.5 turns out on the mixture. Very nice. Before mismatched jets 108&106 AND different heights and bowls set at 19mm vs stock and reset toat 17. Very happy right. Oh and choke now works.

[choneofakind]

Nice!!! Glad someone besides me got good results from my jetting setup That setup ripped pretty well for me, and did well at the track. Now I'm working on my efi tuning, which is a whole new animal. I think I got some good ideas from Scattcatt though, so I'll check that out in the spring.

Did I post that jetting setup in this thread or did you get that somewhere else?? I post so much here I forget where I post things

[RockyCapone]

Originally Posted by choneofakind

Nice!!! Glad someone besides me got good results from my jetting setup

did I post that in this thread or did you get that somewhere else?? I post so much here I forget where I post things

Honestly dont remember where i found it. All remember was you had a older pregen like mine and colored green so if its green it had to be the faster setup. Efi would be nice but i cant see spending that much on a this bike. Maybe next year if i buy a 08-12 model. Damn did i learn a lot quick on this bike. I have a hard time getting over the exhaust note but i guess its like when i was younger we all had big blocks and we heard a honda something with a fart can exhaust but they did move and got my respect. So it is what it is. Thanks

[RockyCapone]

Originally Posted by choneofakind

There's a little capped hose that comes off the bottom of the airbox. Should be about a foot long, give or take a bit. Check your airbox before you freak out about missing a hose from your carbs.

Having a beer and just seen this guy, tomorrow ill find it. Enjoy now. Now thinking do i take it to work or wait. Ill go for it hope no stories of a push tomorrow. Lol

[choneofakind]

Originally Posted by RockyCapone

Honestly dont remember where i found it. All remember was you had a older pregen like mine and colored green so if its green it had to be the faster setup. Efi would be nice but i cant see spending that much on a this bike. Maybe next year if i buy a 08-12 model. Damn did i learn a lot quick on this bike. I have a hard time getting over the exhaust note but i guess its like when i was younger we all had big blocks and we heard a honda something with a fart can exhaust but they did move and got my respect. So it is what it is. Thanks

No problem! Glad it's helping.

I got the bike practically new. The EFI is a tuning project to keep me busy, and the benefits of EFI really compliment the other changes I've made to the bike as well. The bike is now officially everything I want it to be. I just need to tune my fuel table and it will be perfect.

You'll come to like the exhaust a little more. But yeah, it's the farty civic of motorcycles

and yes, green is obviously the fastest.

[RockyCapone]

BTW took bike to work this morning and got on expressway, total different animal, much more power and no problems.