Lower top speed in hot weather??

LoneRonin · May 27th, 2012, 09:33 AM

I've noticed my Ninja has a harder time getting to top speed as of late. The fastest I've gotten was 162km/h (100mph) on the GPS and I wasn't fully tucking or anything.
Recently the weather has been hot, 30C-35C (85F-95F) and on a flat it seems to be stuck at about 145km/h (90mph) with the bike in 6th gear at 11-11.5rpms. I find that to be a pretty significant difference, because when I hit 162 I wasn't fully tucked and didn't have nearly as much road to accelerate.
Also I've noticed a tick-tick-tick noise, its not the typical consistent valve tick I don't think, sometimes I hear it sometimes I don't...I used the screwdriver stethoscope method to listen to the engine and there doesn't seem to be any unusual internal noise..
I wonder if its still contributing to the problem, or if I even have a problem... Its Sunday and all the neighbours have their lawn mowers out, but when its quieter I will try and make a video of the noise. I still have warranty til next season so I'm going to keep riding until anything serious happens, if it does then off to the dealer, but right now I'd rather ride and have it in my garage than theirs...

DaBlue1 · May 27th, 2012, 09:57 AM

Altitude, air temperature, and humidity are factors that will affect how an
engine performs. When the air temperature gets warmer, the engine may run richer, but to get the best performance the engine may need a little more air. Cleaning the air filter may help, but replacing it with one that flows a little more air may be better. see the wiki- http://www.ninjette.org/wiki/Air_filters_for_newgens

Some ticking noises are normal on the Ninja 250. see this thread-http://www.ninjette.org/forums/showp...2&postcount=10

LoneRonin · May 27th, 2012, 10:09 AM

Quote:

Originally Posted by DaBlue1

Altitude, air temperature, and humidity are factors that will affect how an
engine performs. When the air temperature gets warmer, the engine may run richer, but to get the best performance the engine may need a little more air. Cleaning the air filter may help, but replacing it with one that flows a little more air may be better. see the wiki- http://www.ninjette.org/wiki/Air_filters_for_newgens

Some ticking noises are normal on the Ninja 250. see this thread-http://www.ninjette.org/forums/showp...2&postcount=10

Also I should point out I've got two shims under the needles and snorkel removed, I have been experiencing some backfire under hard acceleration. Is there any relation here?

Racer x · May 27th, 2012, 10:43 AM

Humidity and baramereic pressure are adding up to lower power . Water in the air is like a friggin wall . It takes power to move through the heavy water particles. And with high pressure it is worse. The water in the air will not burn and it takes up space that would be occupied by fuel . So you run hot and the mixture is rich because of the lack of oxegen to burn with the fuel.

Whiskey · May 27th, 2012, 03:06 PM

Colder air is denser, denser air has more oxygen/cc so burns more fuel on each power stroke.

You're on a carbed bike, if it's set up for cooler temperatures it'll run rich in warm weather

DaBlue1 · May 27th, 2012, 04:53 PM

Quote:

Originally Posted by LoneRonin

Also I should point out I've got two shims under the needles and snorkel removed, I have been experiencing some backfire under hard acceleration. Is there any relation here?

Popping on decel is common, however backfiring on acceleration is another problem. What else besides shims and snorkel removal do you have going on with your bike? Any other exhaust? Last valve adjustment?

LoneRonin · May 28th, 2012, 07:36 AM

Quote:

Originally Posted by DaBlue1

Popping on decel is common, however backfiring on acceleration is another problem. What else besides shims and snorkel removal do you have going on with your bike? Any other exhaust? Last valve adjustment?

I'm at 44.5k km, no exhuast, valves were last done about 10,000 km ago. I was paying more attention today and rode without earplugs and I noticed it actually happening right when I roll of throttle after hard acceleration, so I think it might just be the popping on decel as you describe.

Also last night was about 10 degrees cooler and I got her up to 161 km in windy conditions, just 1 km short of my top speed so far, so I guess all is good. However the ticking still persists sometime, but I'll just keep riding til she blows, if she does then I'll get it fixed under warranty.

DaBlue1 · May 28th, 2012, 08:27 AM

To help reduce the popping on decel, stop snapping the throttle all the way closed. When you close the throttle completely shut after a high revs, it shuts off fuel and makes for a lean condition which causes the popping sound. Ease off the throttle instead.

CZroe · June 10th, 2012, 07:24 PM

Mine always worked better in the cold. I figured "dense air."

May 27th, 2012, 09:33 AM	#1
LoneRonin ninjette.org sage Name: Jason Location: Mississauga Join Date: Mar 2011 Motorcycle(s): 09 Ninja 250r Posts: 634	Lower top speed in hot weather?? I've noticed my Ninja has a harder time getting to top speed as of late. The fastest I've gotten was 162km/h (100mph) on the GPS and I wasn't fully tucking or anything. Recently the weather has been hot, 30C-35C (85F-95F) and on a flat it seems to be stuck at about 145km/h (90mph) with the bike in 6th gear at 11-11.5rpms. I find that to be a pretty significant difference, because when I hit 162 I wasn't fully tucked and didn't have nearly as much road to accelerate. Also I've noticed a tick-tick-tick noise, its not the typical consistent valve tick I don't think, sometimes I hear it sometimes I don't...I used the screwdriver stethoscope method to listen to the engine and there doesn't seem to be any unusual internal noise.. I wonder if its still contributing to the problem, or if I even have a problem... Its Sunday and all the neighbours have their lawn mowers out, but when its quieter I will try and make a video of the noise. I still have warranty til next season so I'm going to keep riding until anything serious happens, if it does then off to the dealer, but right now I'd rather ride and have it in my garage than theirs...

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May 27th, 2012, 09:57 AM	#2
DaBlue1 Long Time Rider Name: Blue Location: Charlotte, NC Join Date: Sep 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: A lot.	Altitude, air temperature, and humidity are factors that will affect how an engine performs. When the air temperature gets warmer, the engine may run richer, but to get the best performance the engine may need a little more air. Cleaning the air filter may help, but replacing it with one that flows a little more air may be better. see the wiki- http://www.ninjette.org/wiki/Air_filters_for_newgens Some ticking noises are normal on the Ninja 250. see this thread-http://www.ninjette.org/forums/showp...2&postcount=10

May 27th, 2012, 10:43 AM	#4
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	Humidity and baramereic pressure are adding up to lower power . Water in the air is like a friggin wall . It takes power to move through the heavy water particles. And with high pressure it is worse. The water in the air will not burn and it takes up space that would be occupied by fuel . So you run hot and the mixture is rich because of the lack of oxegen to burn with the fuel.

May 27th, 2012, 03:06 PM	#5
Whiskey ninjette.org certified postwhore Name: Morgan Location: A city twinned with Kawasaki Join Date: Nov 2011 Motorcycle(s): '08 Ninja 250, 2010 STR 675 Posts: A lot. Blog Entries: 1	Colder air is denser, denser air has more oxygen/cc so burns more fuel on each power stroke. You're on a carbed bike, if it's set up for cooler temperatures it'll run rich in warm weather

May 28th, 2012, 08:27 AM	#8
DaBlue1 Long Time Rider Name: Blue Location: Charlotte, NC Join Date: Sep 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: A lot.	To help reduce the popping on decel, stop snapping the throttle all the way closed. When you close the throttle completely shut after a high revs, it shuts off fuel and makes for a lean condition which causes the popping sound. Ease off the throttle instead.

June 10th, 2012, 07:24 PM	#9
CZroe CPT Falcon Name: J.Emmett Turner Location: Newnan, GA Join Date: Apr 2009 Motorcycle(s): '08 CP Blue EX250J, '97 unpainted EX250F, 2nd '97 unpainted EX250F (no engine), '07 black EX250F Posts: A lot.	Mine always worked better in the cold. I figured "dense air."