power loss while accelerating hard

[redbike]

When I accelerate hard in first gear, my motorcycle loses power for a second. The engine will make less noise and I will slow down.

Does anyone know what could be the problem?

I was reading the CDI thing but I only notice problems in first gear when I try to accelerate hard. If I accelerate slowly, everything seems fine.

I'm worry it could my the clutch or the gear or something. But my bike is 09 and fairly new. I'm not sure that is problem.

Any ideas would be appreciated.

[Postiez]

Is your bike cold when this happens?

[kkim]

how high is the tach reading when this happens?

[redbike]

Originally Posted by Postiez

Is your bike cold when this happens?

I try to accelerate slowly but i should still happen when it is warm. It does seem a little more likely to happen when i start my bike.

I'll test it when it is warm.

[Postiez]

Originally Posted by redbike

I try to accelerate slowly but i should still happen when it is warm. It does seem a little more likely to happen when i start my bike.

I'll test it when it is warm.

Ya give that a try, even on a warm day if i dont let my bike warm up for a bit that will happen to me

[shporsche]

Yup that happens to me when the bike is cold.
Not fun when trying to cross a intersection and the bike wont move fast to get through the gap.

[Postiez]

Originally Posted by shporsche

Yup that happens to me when the bike is cold.
Not fun when trying to cross a intersection and the bike wont move fast to get through the gap.

haha ya, my house leads right out onto a main highway, bad times

[redbike]

thanks for the help.

i tried accelerating when my bike is warm. it is better. but it does seems like i have low power for the first little bit. I don't know if it is because the RPM is low or because it is the same problem.

It still seems a bit slow in the first .2 seconds

[kkim]

so, the bike acts like it stutters or stalls for a few tenths of a second and then "catches" when in the lower rpms (idle to 4000rpm)?

[redbike]

yes. it seems slower at first. but maybe it is in my head

I have an aftermarket exhaust. I don't think my bike has a jet kit. do you think that could be an issue?

[kkim]

lol... I'm still trying to get a clear picture of what the issue is.

mind starting over for a slow old guy?

[demp]

aftermarket exhaust, has it been re-jetted? I only bring that up because if your bike was running lean, and was cold, I can certainly see this being an issue, (I'm no expert, but I thought I'd ask the question )

[redbike]

no problem kkim.

I guess the only problem is that when i turn the throttle a lot in first gear, sometimes my engine gets very weak. So when i'm in first gear with no throttle and i crack it, instead of going faster, i kind of go slower.

As Postiez said, it is probably because i didn't warm up my engine long enough. It kind sucks. I think i need to warm up my bike quite a bit before the problem is gone.

[kkim]

okay... gotcha.

these bikes do take a long while to warm up. I'd say on the order of 5-10 minutes. If not fully warmed, they can stall and sputter when trying to take off from a stop.

The bikes come lean from the factory which leads to this cold blooded nature. Add to that the fact that the bikes are not always setup the same way when it comes to carb tuning (quality control) and you have some bikes worse that others when it comes to being lean from the factory.

My advice is to shim the carb needles to richen up the mixture a bit.
http://www.ninjette.org/forums/showthread.php?t=9465&

You can also ride off with the choke partially engaged during the first 5-10 minutes to richen up the mixture... just don't forget to turn it off once your bike is fully warmed up on the road.

[g21-30]

Many people think of a "choke" as a plate over the carb, which restricts the air intake; thereby causing a lower air/fuel ration....more gas in relation to the air.

On our bikes, the "choke" is just another jet, which allows gas into the carb. You might say it's like simulating "shimming" the needles. If it helps you to control the bike, prior to total warmup, why not do it (choke it). After the bike is warmed up and more responsive, turn the choke off.

[demp]

Question, can you actually damage the bike if you left the choke on? (I don't... I'm just curious)

[kkim]

some believe you can... I'm not one of them.

[g21-30]

[Greg_E]

The choke is normally a plate that causes higher vacuum in the carb which pulls extra fuel into the mixture, so an extra jet that does the same thing would be a better idea.

[Ntotot]

Originally Posted by demp

Question, can you actually damage the bike if you left the choke on? (I don't... I'm just curious)

it won't damage the bike but you will have difficulties starting the engine later on because of the gas/petrol flooding in the combustion chamber.

i won't spoil my bike with choking when cold... just leave her for 2-5 minutes while having a can of coke/stick of cigarette before making my journey.

[Momaru]

Hmmm, wonder if this is any way related to my bike feeling like it bogs when I grab a handful of throttle from a dead stop, no matter how warm or cold the bike. The first half second seems like the engine's not sure what's going on and rev's drop from idle a bit, then life on the 250 resumes as the engine tops ~4k (will have to try it a few times while really paying attention to confirm that number).

Of course, I'm not sure how the needles are shimmed atm, but I know they are the dynojet needles. Haven't messed with 'em since I bought the bike because, other than me trying to take off from a stop like a budding squid, bike seems happy. Will probably take a look at 'em soon.

[Timm3h]

This is the exact same issue that I am having as well. I am not trying to bring a thread back from the dead, but did anyone find a solution? I have shimmed needles 2 washers, no snorkle, clean carbs, drained tank, replaced gas

[fujimumu]

Make sure your bike is warmed up before you try to go WOT from a dead stop. You can also try to rev the bike up more slowly at first and let the clutch out with the rpm's around 5-6k

[Cedilla]

One night when I took the bike out last summer, it was like I was hitting a dead zone in the rpm range. It was weird, it would pull hard until about 4k, then it would bog until 7k then take off again. It did that through out the whole ride, then never did it again.

I've had quite a few little quirks like that, such as my speedo not working properly one morning, an afternoon ride where the right turn signal was not working, ect. The issues always seem to resolve themselves though.

[alexit69]

bump on this thread

I'm having the exact problems, but it's happening every time I ride. It'll be more pronounced when I first ride off but it's less obvious as I ride along.

This happens more notably in first and a little in 2nd... At around 4000 Rpm, the engine stops pulling even if I crank the throttle a little more. At this point, the tach goes up real slowly and at around 7000 rpm, it catches on again and gives me the usual power. So between 4 and 7000 rpm, i'm literally slowing down and cars are passing me... it's not good for starting from red lights....

After i get off the highway (engine fully warmed) I still feel that around these tach readings, there's a slight loss of power although less pronounced than the times i first leave my starting point.

Maybe it's bc i put too much Seafoam in the batch of gas... someone in another post warned me abt this earlier today, but I don't know if that's the direct effect of putting too much Seafoam in a tank. I'll drain out the gas and put a fresh batch to see if that's the source of my problem.

Somebody has insight on this? How did you fix your problem Redbike and Tim? Thanks everyone

[fujimumu]

I'm not quite sure its a loss of power in that RPM range more than a lack of power that the 250 makes. For me sometimes it seems like opening the throttle too wide in low RPMs makes it harder for the engine to rev up. I usually try to keep the engine running around 6000 RPM and rev to about 4000 while letting the clutch out to get moving from a stop.

[Momaru]

Originally Posted by alexit69

bump on this thread

I'm having the exact problems, but it's happening every time I ride. It'll be more pronounced when I first ride off but it's less obvious as I ride along.

This happens more notably in first and a little in 2nd... At around 4000 Rpm, the engine stops pulling even if I crank the throttle a little more. At this point, the tach goes up real slowly and at around 7000 rpm, it catches on again and gives me the usual power. So between 4 and 7000 rpm, i'm literally slowing down and cars are passing me... it's not good for starting from red lights....

After i get off the highway (engine fully warmed) I still feel that around these tach readings, there's a slight loss of power although less pronounced than the times i first leave my starting point.

Maybe it's bc i put too much Seafoam in the batch of gas... someone in another post warned me abt this earlier today, but I don't know if that's the direct effect of putting too much Seafoam in a tank. I'll drain out the gas and put a fresh batch to see if that's the source of my problem.

Somebody has insight on this? How did you fix your problem Redbike and Tim? Thanks everyone

Any news? Sounds to me like perhaps a bad batch of gas/hiccup for Chris (esp if it resolved after that ride). However yours may be too lean in the midrange. Have you shimmed your needles at all? My try adding a shim or two to richen things up a little.

Regarding too much Seafoam; if you just top off your tank it'll dilute the Seafoam and should fix the issue (if that's it) after a gallon or so, unless you put WAY too much in.

[alexit69]

Hey Mo, sorry i haven't updated my reports yet.

I topped off the tank instead of draining it completely and the problems seems to have been solved (prolly too much Seafoam). However, I think i'll need to shim the needles since I get some hesitation when I cold start the bike and it wears off as the engine gets to riding temp. Lemme describe: when i start the bike after a long rest and start riding, it seems to want to choke when I get on the gas (esp when I give it more gas) AND it doesn't want to rev over 6-7K rpm, but this only happens after i start the bike. After 2-3 min, everything is back to normal. Needless to say, I do warm up the bike while i'm gearing up (abt 1 min or so). I'll shim the needles and remove snorkel and hope to resolve this hesitation after cold starts.

Do you think this'll solve the hesitations or should i just let the bike warm up a lil longer? (I'll prolly shim anyways but just wanted to know the source of this prob)

[fenwaynomar45]

the same thing happened to my bike last night scared me when my headlights lost power. I thought it was because it was cold but 25 minutes into the ride it still did it

[Momaru]

Originally Posted by fenwaynomar45

the same thing happened to my bike last night scared me when my headlights lost power. I thought it was because it was cold but 25 minutes into the ride it still did it

That sounds like a loose electrical connection to me, unless your bike was also acting strange. Even then, I'd suggest checking electricals.

[Momaru]

Originally Posted by alexit69

I topped off the tank instead of draining it completely and the problems seems to have been solved (prolly too much Seafoam).

Glad to hear that was most of it and you salvaged the tank-full. Gas is expendable, but still sucks wasting it.

Originally Posted by alexit69

However, I think i'll need to shim the needles since I get some hesitation when I cold start the bike and it wears off as the engine gets to riding temp. Lemme describe: when i start the bike after a long rest and start riding, it seems to want to choke when I get on the gas (esp when I give it more gas) AND it doesn't want to rev over 6-7K rpm, but this only happens after i start the bike. After 2-3 min, everything is back to normal. Needless to say, I do warm up the bike while i'm gearing up (abt 1 min or so). I'll shim the needles and remove snorkel and hope to resolve this hesitation after cold starts.

Do you think this'll solve the hesitations or should i just let the bike warm up a lil longer? (I'll prolly shim anyways but just wanted to know the source of this prob)

A jetting problem that gets better as the bike warms up usually indicates a lean condition. Shimming the needles and/or backing the mixture screws out will richen the mid and low power bands respectively (which carb part works where in the band is considerably more complicated than that, but that's the short version). Removing the snorkel will allow more airflow thereby 'leaning' the air/fuel mixture. If you decide to adjust the carbs, I'd suggest pulling the snorkel first as that will impact your final tuning setting.

[alexit69]

thanks for the tip! I'll prolly be doing that this week!

[omnivore]

Riding with choke on will also foul plugs sooner, and possibly result in deposits in combustion chambers and on valves if done for long time.


Your issue could be fuel filter or kinked fuel line. Sounds like fuel delivery issue to me.