The carbs work on a vacuum so that's why you get a small lag when cracking open the throttle at idle. With the HMF Exhaust you may want to consider at least shimming the needles if it has not already been done. If you plan to remove the snorkel then you will definitely have too.
250R is bogging down (or something?)
I've got a 2008 Ninja 250R. The previous owner put a HMF Performance muffler on it. (It sounds fantastic btw) But it doesn't idle very smooth, and the throttle response is wonky. I got a hold of HMF, and they informed me that it was a low restriction pipe and the bike would need a high performance air filter and re-jetted to run right.
I picked up a K&N air filter today, but if anything, the throttle response is worse. If I roll on the throttle real slow, I get a nice steady climb in the RPM's. (This is just sitting on the stand, no load). If I snap the throttle real quick though, it hits 2K RPM and waits a bit, before it starts to climb. I'm not terribly familiar with engines, let alone ones with carburetors. Is it not getting enough fuel now? Why does it behave differently when I throttle up slow? Should I put the original filter back in for now? Does anyone have any experience with jetting a 250?
I would have rather left it alone, but with the muffler it has on it currently I think I need to finish the job.
Thanks for any advice.
Also, to everyone affected by the recent storms I hope you and your family are safe and well.
I picked up a K&N air filter today, but if anything, the throttle response is worse. If I roll on the throttle real slow, I get a nice steady climb in the RPM's. (This is just sitting on the stand, no load). If I snap the throttle real quick though, it hits 2K RPM and waits a bit, before it starts to climb. I'm not terribly familiar with engines, let alone ones with carburetors. Is it not getting enough fuel now? Why does it behave differently when I throttle up slow? Should I put the original filter back in for now? Does anyone have any experience with jetting a 250?
I would have rather left it alone, but with the muffler it has on it currently I think I need to finish the job.
Thanks for any advice.
Also, to everyone affected by the recent storms I hope you and your family are safe and well.
1 - 20 of 28 Posts
What is the snorkel? That pops up everywhere I look at jetting the bike... Also, I don't believe it has been shimmed or anything else. It had the original air filter, brakes, tires, oil filter. If all the simple stuff wasn't done, I would be surprised that the carbs/tuning had been adjusted.
I hate to rob low end torque for extra horsepower. I'm heavy so the bike needs the torque. Really I just want it to run right.
I've got a pair of sport demons to put on it, ebc HH pads for the front and GG for the rear. I've changed the oil and filter, it's mobile 1 synthetic now. I've also put in the K&N air filter. (Tried cleaning the original, honestly it seemed to work better) I'm considering replacing the front springs but figure I should actually ride it some more first. I've considered stainless steel brake lines, though I doubt it needs it. There are some cosmetic things I would like to do after the mechanical. Stickers, lights. Visibility and flair.
I hate to rob low end torque for extra horsepower. I'm heavy so the bike needs the torque. Really I just want it to run right.
I've got a pair of sport demons to put on it, ebc HH pads for the front and GG for the rear. I've changed the oil and filter, it's mobile 1 synthetic now. I've also put in the K&N air filter. (Tried cleaning the original, honestly it seemed to work better) I'm considering replacing the front springs but figure I should actually ride it some more first. I've considered stainless steel brake lines, though I doubt it needs it. There are some cosmetic things I would like to do after the mechanical. Stickers, lights. Visibility and flair.
The snorkel is the first part of the air box. It is on the right side of the bike... take the seat off and the black side piece and you'll be able to pry it out from behind the airbox with a flat head screw driver... it is rubber and will pop right out...
Thanks for the links.
I put a K&N air filter in, even ran it for a minute with the side cover off (there is some gunk in the snorkel(?) that i didn't want flying into the carbs) so I don't think air restriction is the issue at the moment. If i crank the throttle hard from idle, it jumps from 1300 (idle) to 2000 rpm, pauses, then revs up higher. If I crank it too hard from idle, it stalls. Mind you I didn't let the engine really warm up today.
Even in 95 deg. weather the engine has to warm up. I don't understand why that is. It runs pretty good once it's warm, but I guess lag at lower RPM is a good way to describe it.
When I open the throttle what happens? Does it introduce more fuel to the engine? Air? Both? If it is getting enough air, how can it not be getting enough fuel? The bike does not have a fuel pump, correct? How does fuel get forced into the engine anyways, gravity?
I realize the solution is simple; take the bike and my wallet to a reputable mechanic. But I'm curious what the hell the thing is doing.
I put a K&N air filter in, even ran it for a minute with the side cover off (there is some gunk in the snorkel(?) that i didn't want flying into the carbs) so I don't think air restriction is the issue at the moment. If i crank the throttle hard from idle, it jumps from 1300 (idle) to 2000 rpm, pauses, then revs up higher. If I crank it too hard from idle, it stalls. Mind you I didn't let the engine really warm up today.
Even in 95 deg. weather the engine has to warm up. I don't understand why that is. It runs pretty good once it's warm, but I guess lag at lower RPM is a good way to describe it.
When I open the throttle what happens? Does it introduce more fuel to the engine? Air? Both? If it is getting enough air, how can it not be getting enough fuel? The bike does not have a fuel pump, correct? How does fuel get forced into the engine anyways, gravity?
I realize the solution is simple; take the bike and my wallet to a reputable mechanic. But I'm curious what the hell the thing is doing.
The muffler most likely leaned the mixture slightly (it's usually already lean from the factory for emission reasons), and adding a free-flow filter like the K&N will make the problem worse.
You may need to install a Jet Kit, or shim the needles, to richen the mixture to get it to run right. I'd go back to the stock filter for now, and remove the caps on the idle mixture screws so you can adjust the mixture to get it to idle smoothly. Richening the idle mixture (especially if it's way off - lean) should get you some improvement.
Look this over for some info on carbs and how they work - http://www.newninja.com/forums/f97/carb-and-jetting-info-links-6729.html
Jay
You may need to install a Jet Kit, or shim the needles, to richen the mixture to get it to run right. I'd go back to the stock filter for now, and remove the caps on the idle mixture screws so you can adjust the mixture to get it to idle smoothly. Richening the idle mixture (especially if it's way off - lean) should get you some improvement.
Look this over for some info on carbs and how they work - http://www.newninja.com/forums/f97/carb-and-jetting-info-links-6729.html
Jay
Running the engine with the side cover off introduces too much air, which the result will be crappy running. Remove whatever is stuck inside your snorkel. Blocked airflow in the snorkel is a problem......I put a K&N air filter in, even ran it for a minute with the side cover off (there is some gunk in the snorkel(?) that i didn't want flying into the carbs) so I don't think air restriction is the issue at the moment.
Despite the fact that the ambient temp is 95, your cylinder, oil and fuel temps are not. Proper temps equal better combustion. That's why a warm up is necessary. A properly warmed engine is important especially in a carbed engine. Unlike EFI bikes the carbs can not compensate (air/fuel) for temp changes. You can't crack the throttle open on a cold engine or it will lag and stall. The CV carbs work on a vacuum, so there is going to be a natural lag coming off idle.
Add 2-3 shims to your stock needles and remove the snorkel if you what a small low end and mid-range boost or re-jet. Your choice.
I'll put the K&N back in it, warm it up and take it out today. I was counting on having to have it rejetted, but I'll look into the shims too.
I'm still ignorant of how the bike works. Thank you everyone for all of the input.
I'm still ignorant of how the bike works. Thank you everyone for all of the input.
Played with the filter a bit this morning. Ended up with the stock filter back in it. Let it warm up, and the stalling issue went away. Took it out on the highway (first time) didn't have any issues.
That's good news eh! Let us know how it holds up after a few rides.
:Sent via the NewNinja App:
:Sent via the NewNinja App:
The main issue is that it needs to be jetted and the needles need to be raised. I have the dynojet jet kit and I went one up on the jet and on the 2nd mark on the needle. I'm only getting 47 mpg, so I think my needle is a little high. I have the HMF muffler & K&N air filter as well. Response is great and I hardly need to use the choke. I had the r-0990 in at one point but put the air box back in. I didn't want to be caught out in the rain and be worried about it.
You need to find out how to get the right amount of fuel in there. The only way to truly figure out if our carb bikes are running right is if it is on a dyno that samples the exhaust for the proper air/fuel ratio. There are air/fuel gauges that install a O2 sensor for 170 or so. The O2 sensor needs to be installed on the exhaust pipe.
You need to find out how to get the right amount of fuel in there. The only way to truly figure out if our carb bikes are running right is if it is on a dyno that samples the exhaust for the proper air/fuel ratio. There are air/fuel gauges that install a O2 sensor for 170 or so. The O2 sensor needs to be installed on the exhaust pipe.
Wow, that's a bit more involved than I wanted to get. I may ask around for settings from people who have installed the Dynojet kit and see what has worked for others, rather than put the bike on a dyno. Let me know if you adjust the needle back a bit.yoursailor05 said:The main issue is that it needs to be jetted and the needles need to be raised. I have the dynojet jet kit and I went one up on the jet and on the 2nd mark on the needle. I'm only getting 47 mpg, so I think my needle is a little high. I have the HMF muffler & K&N air filter as well. Response is great and I hardly need to use the choke. I had the r-0990 in at one point but put the air box back in. I didn't want to be caught out in the rain and be worried about it.
You need to find out how to get the right amount of fuel in there. The only way to truly figure out if our carb bikes are running right is if it is on a dyno that samples the exhaust for the proper air/fuel ratio. There are air/fuel gauges that install a O2 sensor for 170 or so. The O2 sensor needs to be installed on the exhaust pipe.
I didn't dyno it. The "bogging down" is a symptom that you can use to solve the problem. In the higher RPM the needle is used to adjust the fuel. You can shim the needle up and call it good. If it starts and gets from 1,400 to 4,000 fine you wouldn't necessarily need to put the next step up in jets. To shim the needle you can use a couple of small washers. You can get the small ones to fit from Radio Shack. It's a small package that comes with a verity of washers.
I just put my HMF pipe on, and i feel like i have the same issues that went on here.... But im not very mechanical, and i think i'll need to take it in... xD It's been interesting reading this, thanks. Also very helpful.
It makes the little bike sound good though doesn't it?Ninjeff said:I just put my HMF pipe on, and i feel like i have the same issues that went on here.... But im not very mechanical, and i think i'll need to take it in... xD It's been interesting reading this, thanks. Also very helpful.
I may post some videos of the bike this weekend; before & after warming up.
Boy does it ever.... As soon as i started it up after the install i jumped for joy. The sound is so fantastic. But i can easily tell it needs work. I'm a really new rider, being 20, this is my first vehicle EVER. And i love it. Rain or shine.It makes the little bike sound good though doesn't it?
I may post some videos of the bike this weekend; before & after warming up.
That being said, it needs to be rejetted. It backfires and i am noticing a difference in throttle areas. But i'm still way too inexperienced to muck around with my brand new bike. So i'll be bringing it in this weekend, hopefully.
That's interesting, because mine doesn't backfire. I almost get a miss or something when engine braking, but again out on the highway yesterday I didn't notice anything. Can you describe what is different now with the throttle?Ninjeff said:Boy does it ever.... As soon as i started it up after the install i jumped for joy. The sound is so fantastic. But i can easily tell it needs work. I'm a really new rider, being 20, this is my first vehicle EVER. And i love it. Rain or shine.
That being said, it needs to be rejetted. It backfires and i am noticing a difference in throttle areas. But i'm still way too inexperienced to muck around with my brand new bike. So i'll be bringing it in this weekend, hopefully.
I'm making an assumption with my bike that the carbs were not adjusted to match the exhaust. (Wouldn't the air filter be necessary?) Hopefully a video or two will give some of the more experienced folks watching this thread some insight into what I've got. (Since I seem not to have a clue
I can clearly hear the backfires on mine... maybe i installed it incorrectly? XD I duno. With throttling, i do notice what you said about your throttle, but i also feel like mines a bit slower starting off. Less power, but that could also be in my head, or how i've been throttling to clutch ratio. The two things i want to get checked are the backfires and the mileage. I've noticed im getting about 80-90 Kilometers with a half tank, where as before with stock i was getting 100-110.
Is backfiring bad for my engine? As i said before i really don't know much.
Is backfiring bad for my engine? As i said before i really don't know much.
Maybe what im hearing is back chatter... which is apparently different... Lol... I don't know.
1 - 20 of 28 Posts
- This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Kawasaki Ninja Forum
A forum community dedicated to Kawasaki Ninja owners and enthusiasts. Come join the discussion about performance, modifications, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Recommended Communities
