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Discussion Starter #1
Hello all,

this is my very first motorcycle and yes I am a newb so I apologize for any ignorance in advance.

i tried searching many a times for an answer here but to no avail.

Here's the deal. My bike runs great while riding around town in streets. When i get on the freeway and go ~80 mph and above my bike will run a couple of miles great. But after a while it will suddenly lose power (bog down) and start dropping speed down to 65. I will give it full throttle but the bike will keep dropping speed or just hold the speed at ~65mph. If I happen to release the throttle the speed will drop and if given more throttle it will stay at that lower speed and not go faster till I pull over.

I have to get off and the engine will sometimes die when coming to a stop. I wait a few seconds and restart it with the choke and it goes fine and will ride the streets no problem.

What is wrong with my bike????? Is it the engine, fuel system, is it overheating??? Is it a fixable problem??? Am I not letting it warm up long enough???

Is this normal since its a 250cc and isn’t built to ride at 80 mph to 90 mph for a long period of time (I’m guessing)???

HEEEELP!

I have not experienced this problem while going 65-70 mph for long rides on the freeway. Only when I ride higher speeds for an extended period of time ~5-10 miles.

bike specs
2008 ninja 250r stock
bought it used with 1800 miles on it

Other examples to be more specific. All separate days.

1st time Happened (Orange county, ca. 6:45 am)
started my bike, let it warm up, road onto freeway. started going average 85 - 90 mph. about 8-10 miles down the freeway, it suddenly started losing power and dropping speed. I gave it w.o.t. and still slowed down and engine wouldn't speed up. it stopped dropping to 65mph then it maintained there unless I slowed it down then it would stay at that lower speed 50 mph. Scary when 18 wheelers are passing you lol!

exited and turned off the engine, let it cool down for 1 minutes, started fine and ran fine street wise. so got back on and SAME THING HAPPENED AGAIN going 85 mph only at a shorter distance ~4 miles. It wouldn’t start unless I put the choke, then rode fine in streets again.

2nd time. (Orange county, ca. 6:45 am)

Same thing happened only I was going average 75-80 mph. It lasted a little longer, but same situation happened only the engine did turn off when coming to stop.

3rd time (Orange county, ca. 5:50 P.M.)
Same as 2nd time, engine died coming to a stop.

4rth time (Orange county, ca. 2:00 AM)
Same thing, only going average 75 mph bout 8 miles down freeway. Engine did die when I was coming to a stop.

I just wait a minute or little less, put the choke on, then it starts and run like a beauty in streets.

Any help would be appreciated, if need any more specifics please ask.

Thank you!
 

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You say you bought it used. Give us the history. Mods? Condition?

Do some basic maintenance on it: Drain out the bowl, clean out carb, check that the vacuum diaphragm is not pinched/ripped, spark plugs are not fouled, etc.
 

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The Indifference Engine
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You may have a clogged breather in the gas tank gas cap. What happens is it lets air in as the gas goes out, if it is clogged then you develop a vacuum that can be strong enough to prevent gas from getting into the carbs, or slow down the rate at which it gets into the carbs. Which would either kill the bike or limit its speed depending on how fast it was getting in there. The best test for this is to actually ride the bike until it dies/bogs like you were saying and when it happens pull over, rip off your helmet and pop the gas cap. If you hear a "whoosh" noise like air being sucked into the tank then you'll have to clean out the breather.

Other possibilities include the wrong size mainjet or an improperly installed one. Or a vacuum leak at the carbs.
 

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I was actually going to suggest the whole gas cap thing, when I had my old bike I stalled for no reason and I couldn't figure out why and after sitting on the side of the road trying to get the stupid thing to start and calling the dealership, I popped the gas cap to make sure there was enough gas in the tank and voila! The bike worked just fine! I felt really stupid but was really grateful that it was as simple as that.
 

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I was actually going to suggest the whole gas cap thing, when I had my old bike I stalled for no reason and I couldn't figure out why and after sitting on the side of the road trying to get the stupid thing to start and calling the dealership, I popped the gas cap to make sure there was enough gas in the tank and voila! The bike worked just fine! I felt really stupid but was really grateful that it was as simple as that.
What year bike was this on?

That's never happened to me: Old gen and not.

But if that's the case wouldn't that suggest one of the evap lines are plugged, when they shouldn't be?
 

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Is this normal since its a 250cc and isn’t built to ride at 80 mph to 90 mph for a long period of time (I’m guessing)???

HEEEELP!

I have not experienced this problem while going 65-70 mph for long rides on the freeway. Only when I ride higher speeds for an extended period of time ~5-10 miles.


Thank you!

Mine runs great and strong at 80-90 MPH+ @ 11,000-12,000RPMs for 3 hours on the highway during my trips up to my cousins house on the weekends! :p

250cc is built for highways.



Aside from the vaccum possible issue, does your bike poof smoke behind you while riding it?

could also be the valves need adjusting. how many miles on your bike ATM?
 

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Discussion Starter #7
@Devilrey

The bike is stock for what i know, it was dumped once but not to bad.

@ Sev

I will test it out the gas thing tank this weekend.


  • I have never worked on a bike (my first bike) so it should interesting to take it apart and work on it :eek:.
  • Are these tasks hard to do (wrong size main jet or an improperly installed one. Or a vacuum leak at the carbs, valve adjustment)???
  • Any suggested links with steps for these procedures?
@ ScorpianNinja

It has 2543 miles and i only put 671 since buying her from a motorcycle shop. 1873 miles when purchased


  • No Smoke comes out of the tail pipe at all
Thank you for the advice people, i will follow up with you when i test the gas tank tomorrow! Pray for the best for me please!

Much appreciated and God Bless:)
 

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The Indifference Engine
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What year bike was this on?

That's never happened to me: Old gen and not.

But if that's the case wouldn't that suggest one of the evap lines are plugged, when they shouldn't be?
Yes, that's exactly what I suggested.

@ Sev

I will test it out the gas thing tank this weekend.


  • I have never worked on a bike (my first bike) so it should interesting to take it apart and work on it :eek:.
  • Are these tasks hard to do (wrong size main jet or an improperly installed one. Or a vacuum leak at the carbs, valve adjustment)???
  • Any suggested links with steps for these procedures?
The gas cap bit is easy. The rest... well it's complicated but not difficult, there are write ups all over the place. Just be methodical and you'll be fine.

I won't be valves, valves don't cause that problem.
 

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Sooooooo did anyone figure this out.... cause im still having this problem!!!! I heard it might be gas cap but I can smell gas so its rather leaking out instead of sealing it all in right?
 

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You may have a clogged breather in the gas tank gas cap. What happens is it lets air in as the gas goes out, if it is clogged then you develop a vacuum that can be strong enough to prevent gas from getting into the carbs, or slow down the rate at which it gets into the carbs. Which would either kill the bike or limit its speed depending on how fast it was getting in there. The best test for this is to actually ride the bike until it dies/bogs like you were saying and when it happens pull over, rip off your helmet and pop the gas cap. If you hear a "whoosh" noise like air being sucked into the tank then you'll have to clean out the breather.

Other possibilities include the wrong size mainjet or an improperly installed one. Or a vacuum leak at the carbs.
This is very interesting , and altough I recon that it probably won't be safe , could you just keep an extra key on the gas tank and pop the gas tank cap open when just when it happens to see if it corrects?
 

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This is very interesting , and altough I recon that it probably won't be safe , could you just keep an extra key on the gas tank and pop the gas tank cap open when just when it happens to see if it corrects?
but it seems like my gas cap isnt sealing.. I smell gas sometimes , specially in the garage but I turn it on outside .
 

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This problem is exactly the reason why I joined the forums today. My Ninja 250R is experiencing the same problems at the moment, but it's totally new. Mine has just under 6200 miles on it, 3800 of them are my own that I've put on the bike over the past couple of months (yes, I ride it quite a bit, and I LOVE it haha) initially the bike ran like a charm, I've gone on several 100+ mile road trips with it, but right as soon as 6k miles rolled around, I'm experiencing the same dramatic loss of power on the freeways that you are, only mine are sporadic. Sometimes it works fine, sometimes it doesn't. Other than that, our problems are identical. I put it in the shop (today marks the THIRD DAY those guys have had it and still aren't 100% sure of what the problem is since they can't replicate the problem due to mine being sporadic) but they DID discover that my fuel mixture fluctuates drastically as it's running. The mechanic said that my bike starts "dangerously" lean and remains dynamic as the bike continues to run. Now my bike does have quite a few aftermarket parts on it that I did not install, everything on my bike is from the previous owner, but perhaps if I can find a solution to my problem, it will assist you in finding yours. I will be picking my bike back up tomorrow and getting my own tools to perform maintenance with, I don't like depending on a shop mechanic to take care of my bike, I'd much rather learn it myself. Just make sure you pick up a copy of the service manual before you decide to try it yourself as well.

Good Luck, and Best Wishes!

Zach
 

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I ♥ Cute Cats!
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but it seems like my gas cap isnt sealing.. I smell gas sometimes , specially in the garage but I turn it on outside .
You smell gas because gas is leaving the gas cap: That is normal. Otherwise pressure would build until something blew up.

What Slev is talking about is air being able to ENTER the tank. As fuel leaves the tank if you don't replace that volume with something (say AIR) you will create a vacuum inside your tank and get exactly the condition you've described. If the bike dies and you pull over and open your fuel cap and hear a "WOOOOOSH" sound: You've found your problem.

You mentioned you're in California and with the California 250's air is allowed to ENTER the tank via one of two hoses:

In this example the emissions equipment is removed and I chose to leave the center port (the one with the blue dot) open to allow air to enter the tank and I plugged the red. If either of those 2 ports are clogged you WILL run into problems with stalling.

This problem is exactly the reason why I joined the forums today. My Ninja 250R is experiencing the same problems at the moment, but it's totally new. Mine has just under 6200 miles on it, 3800 of them are my own that I've put on the bike over the past couple of months (yes, I ride it quite a bit, and I LOVE it haha) initially the bike ran like a charm, I've gone on several 100+ mile road trips with it, but right as soon as 6k miles rolled around, I'm experiencing the same dramatic loss of power on the freeways that you are, only mine are sporadic. Sometimes it works fine, sometimes it doesn't. Other than that, our problems are identical. I put it in the shop (today marks the THIRD DAY those guys have had it and still aren't 100% sure of what the problem is since they can't replicate the problem due to mine being sporadic) but they DID discover that my fuel mixture fluctuates drastically as it's running. The mechanic said that my bike starts "dangerously" lean and remains dynamic as the bike continues to run. Now my bike does have quite a few aftermarket parts on it that I did not install, everything on my bike is from the previous owner, but perhaps if I can find a solution to my problem, it will assist you in finding yours. I will be picking my bike back up tomorrow and getting my own tools to perform maintenance with, I don't like depending on a shop mechanic to take care of my bike, I'd much rather learn it myself. Just make sure you pick up a copy of the service manual before you decide to try it yourself as well.

Good Luck, and Best Wishes!

Zach
You haven't let the bike sit for any extended periods of time (yeah you said you ride it a lot, but in the past month or two?). Also is your bike a Cali bike or not?
 

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@VeX
I've never allowed my bike to sit for more than probably 20-22 hours since the day I got it which was a couple of months ago. (I literally ride the bike every single night) However, the guy I purchased it from is a currently deployed soldier (his reason for selling the bike) I have no idea how long the bike was sitting from the time he deployed to the time I purchased it, however I don't believe that problems from it sitting would have risen up over 3000 miles later though I could quite possibly be mistaken. And no, I didn't catch that part of this thread, I purchased my bike in Arizona, and I reside in Nevada. I am the third owner, and I do not know where the first owner bought the bike
 

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You smell gas because gas is leaving the gas cap: That is normal. Otherwise pressure would build until something blew up.

What Slev is talking about is air being able to ENTER the tank. As fuel leaves the tank if you don't replace that volume with something (say AIR) you will create a vacuum inside your tank and get exactly the condition you've described. If the bike dies and you pull over and open your fuel cap and hear a "WOOOOOSH" sound: You've found your problem.

You mentioned you're in California and with the California 250's air is allowed to ENTER the tank via one of two hoses:

In this example the emissions equipment is removed and I chose to leave the center port (the one with the blue dot) open to allow air to enter the tank and I plugged the red. If either of those 2 ports are clogged you WILL run into problems with stalling.



You haven't let the bike sit for any extended periods of time (yeah you said you ride it a lot, but in the past month or two?). Also is your bike a Cali bike or not?

I have the 97 zx6r but mines not a twist on gas cap its the one with the key and it doesnt make a noise when I open the gas cap
 

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ok I have limited amount of experience on bikes but I worked on cars for a long time , being that these bikes are carburators , carburators have a fuel reserve on a little tank that is there for times when the fuel pump temporarily loses feed from the fuel tank , which usually is very short , (under hard acceleration on a uphill for example , hard breaking , bump etc...) but it sounds to me that is definitely fuel related , so... if I am correct it sounds to me that for some reason the pump is not able to keep the reserve in the carburetor with enough fuel at high speeds it can be due to the following :

1:is your bike leaned to the front for some reason ? (different suspension , tires etc ..)

2:twisted fuel hose would prevent enough fuel to flow to the carburetors for extended periods of time resulting in Carb reserve to dry up eventually as it cannot flow enough fuel into the carburetor under high demand such as driving at high speeds .

3:Bad fuel pump ( I don't even know if bikes have fuel pumps or it is gravity alone )

4:eek:bstruction of fuel filter or a dirty one would do the same as number 2 .

again these are based on car knowledge but it sounds logical to me..

PD:a vacum formed in the fuel lines could do this too , I don't know if bikes have pressure releif valves that let's the pressure go , (think of a straw with water inside , if you put your finger on top of the straw it would hold the liquid in place due to vacuum pressure .

edit2:letting the bike rest and sit there would allow the carburator reserves to fill up again fixing the problem temporarily, so that is why it works after letting it sit there.

Can anyone give an opinion on my theory ?
 

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ok I have limited amount of experience on bikes but I worked on cars for a long time , being that these bikes are carburators , carburators have a fuel reserve on a little tank that is there for times when the fuel pump temporarily loses feed from the fuel tank , which usually is very short , (under hard acceleration on a uphill for example , hard breaking , bump etc...) but it sounds to me that is definitely fuel related , so... if I am correct it sounds to me that for some reason the pump is not able to keep the reserve in the carburetor with enough fuel at high speeds it can be due to the following :

1:is your bike leaned to the front for some reason ? (different suspension , tires etc ..)

2:twisted fuel hose would prevent enough fuel to flow to the carburetors for extended periods of time resulting in Carb reserve to dry up eventually as it cannot flow enough fuel into the carburetor under high demand such as driving at high speeds .

3:Bad fuel pump ( I don't even know if bikes have fuel pumps or it is gravity alone )

4:eek:bstruction of fuel filter or a dirty one would do the same as number 2 .

again these are based on car knowledge but it sounds logical to me..

PD:a vacum formed in the fuel lines could do this too , I don't know if bikes have pressure releif valves that let's the pressure go , (think of a straw with water inside , if you put your finger on top of the straw it would hold the liquid in place due to vacuum pressure .

edit2:letting the bike rest and sit there would allow the carburator reserves to fill up again fixing the problem temporarily, so that is why it works after letting it sit there.

Can anyone give an opinion on my theory ?


Actually I let mine sit for an hour and it still wouldn't star,
 

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Alright, sorry for the delay. Turns out I got the bike back today, they rejetted it for me since it was running lean (a job that I will be doing myself from now on because I think it's ridiculous that it takes them 4 days to do that) but the bike is running great. I put probably somewhere around 50 miles on it today after I got it from the shop. Nothing seemed to be wrong aside from the bike idling at only 1k rpm, sometimes a little less, but that's an easy fix I'll get to tomorrow. Now 50 miles is no where near a large enough time for me to determine if my 250 is 'fixed', because it only ran into these types of problems maybe once out of every 700 miles or so. I'll keep you up to date after I put another 1000 miles on it and let you know if mine acts up. My recommendation? Along with all of the other possibilities to check into, make sure your's wasn't too lean like mine was.
 

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Alright, sorry for the delay. Turns out I got the bike back today, they rejetted it for me since it was running lean (a job that I will be doing myself from now on because I think it's ridiculous that it takes them 4 days to do that) but the bike is running great. I put probably somewhere around 50 miles on it today after I got it from the shop. Nothing seemed to be wrong aside from the bike idling at only 1k rpm, sometimes a little less, but that's an easy fix I'll get to tomorrow. Now 50 miles is no where near a large enough time for me to determine if my 250 is 'fixed', because it only ran into these types of problems maybe once out of every 700 miles or so. I'll keep you up to date after I put another 1000 miles on it and let you know if mine acts up. My recommendation? Along with all of the other possibilities to check into, make sure your's wasn't too lean like mine was.
You know I really wish I could tell if it was running lean or not, plus jetting it, I don't know anything about bikes let alone carbs
 
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