ninja 250 - revving higher than usual

[superspud9]

Hey Guys,

So ive noticed these past two days on my highway commute that my 09 250 has been hitting close to 9k RPM at 100km/h in 6th gear when it usually revs at 8K RPM at 100km/h. Ive noticed this these past two days which have been extremely hot out (like 30 degrees i think), so could the heat have something to do with the higher revs? It seems like its revving a bit higher than usual in all gears, but i really noticed in 6th gear cause i always check how its revving when i hit 100km/h.

Also, im not sure if im just imagining it now but my throttle response feels different now. It seems like i don't have to open the throttle as much as i used to to accelerate between gears (like before say i would have to open throttle like 30degrees, now it seems i only open it like 15degrees and get the same result)
I checked the throttle cable and it *appears* to be working just fine

Any ideas on what could be going on? would the weather be a factor to consider??

edit: if it helps, the idle is set to around 1300rpm and i havent changed it

Thanks

[Bmart]

my 09 250 is doing the same thing right now. anyone have any ideas??

[mxs]

The weather (temperature, humidity, pressure etc.) affects air/fuel ratio, so yes it's most likely normal what you are experiencing. If your bike was fuel injected the ECU would adjust for that, but no chance with a carburetted bike .... not until you rejet, which for this type of bike and use makes no sense, unless you decide to move and you would ride in constantly different conditions.

BTW, typically hotter weather means the bike will run a bit richer (fuel/air ratio ....).

[mikbusa]

Ninja 250 tachometers 08+ are notorious for inaccuracy in the heat. Your bikes fine.

[Bmart]

The tach seems to be as accurate as it ever was. I definitely notice the higher RPM's. (noticeably more vibrations). The bike behaves perfectly normal on my ride to work in the morning (55-60F) and on the way home the bike would start revving 1000RPM exactly higher than normal at 100km/h, the weather was up to about 75 degrees F... But it would take 5 minutes or so to start creeping up.

So the heat seems to be the culprit.. But im curious how this bike will be in the summer heat? When it hits 90F...

Thanks for the responses guys,

Brian

[dossantos25]

could also be the rad fans turning on, i notice at idle the rpms will bump up a bit to cope with the load the ran fans place on the charging system.

[SweetOnion]

The engine is directly connected to the wheels are directly connected to the ground.

If your motor was not even running and you pushed the bike at 100kph, the rpm's would still be the exact same as any other time. I don't know anything of Ninja 250's tachometer accuracy but that sounds like the most likely cause to me.

[HorizonXP]

This sounds like the Engine ECU problem that a number of people have complained to Kawasaki about, to no avail. Look it up on Ninjette forums. Basically, you can attempt to fix it by replacing it with a pre-gen ECU, but it's basically a design flaw because they didn't provide the circuity adequate cooling.

[djltoronto]

The engine is directly connected to the wheels are directly connected to the ground.

If your motor was not even running and you pushed the bike at 100kph, the rpm's would still be the exact same as any other time. I don't know anything of Ninja 250's tachometer accuracy but that sounds like the most likely cause to me.

That, or the speedometer accuracy varies with heat - yielding the same result.



Is the speedo cable driven on the Ninja 250?

[djltoronto]

The weather (temperature, humidity, pressure etc.) affects air/fuel ratio, so yes it's most likely normal what you are experiencing. If your bike was fuel injected the ECU would adjust for that, but no chance with a carburetted bike .... not until you rejet, which for this type of bike and use makes no sense, unless you decide to move and you would ride in constantly different conditions.

BTW, typically hotter weather means the bike will run a bit richer (fuel/air ratio ....).

None of that affects the relationship between Engine RPM and vehicle speed - in a fixed gear.

[TheDirty]

None of that affects the relationship between Engine RPM and vehicle speed - in a fixed gear.

True story.

For there to be an actual RPM difference at the same speed and gear there would have to be some slippage between the engine and the drive wheel. Assuming your clutch isn't slipping and you haven't changed a sprocket or gotten a different sized wheel/tire, then the only explanation is an inaccurate tach.

[djltoronto]

True story.

For there to be an actual RPM difference at the same speed and gear there would have to be some slippage between the engine and the drive wheel. Assuming your clutch isn't slipping and you haven't changed a sprocket or gotten a different sized wheel/tire, then the only explanation is an inaccurate tach.

Or an inaccurate speedo. Either one of the 2 gauges in question is off.

[TheDirty]

Or an inaccurate speedo. Either one of the 2 gauges in question is off.

Oops, right.

[murf]

Are you guys in 5th gear instead of 6th?

[mxs]

None of that affects the relationship between Engine RPM and vehicle speed - in a fixed gear.

To think of it further, it makes sense what you are saying. However, what got me thinking again was him mentioning the throttle position and how the engine revs easier in each gear and talking about a different throttle response (so it's not just the RPMs on the clock ...). If the speedo reports faulty RPMs in higher ambient temps, the throttle applied would still feel identical, would it not? (meaning no change in a/f and thus throttle response). To me throttle response is always linked to a/f ratios ...