Rejetting - what time of year?

headshrink · January 11th, 2009, 02:31 AM

Rejetting will likely be the next thing I do to my bike, if I don't go with the heated jacket first (just ordered gloves).

Since there are so many factors in rejetting, I was wondering how much it mattered which season, or what the weather is like, when this work is done. I am in CA and ride 12 months out of the year to commute to work. It is hot in the summer (90's - low 100's) and moderately cold in the winter (30's-50's).

I don't know if any of this matters, but then again.... that is my question.

Viper-Byte · January 11th, 2009, 02:45 AM

From what I believe, the temperature has got apart to play in it as the density of the air and how much gets into the engine is related on the air temp, I THINK the hotter it is, the denser the air is, colder the other way round.

You could rejet on a day that is an avg temp over the whole year, this will give a bike with the best power at the mid temps (as this is what you would tune for) or, you could tune (shimming the needles) when the temps get hotter and colder, this will gove you the most power for that temp range, but requires shimming more often.

Note, take my advise with a grain of salt, this is what I believe and I am new to this, so I could be wrong, wait for the others to advise.

headshrink · January 11th, 2009, 03:19 AM

Thanks.

Cold air is denser, but I know what you meant

Viper-Byte · January 11th, 2009, 04:38 AM

NP

Well I had a 50/50 chance of getting it right, I guess I should have looked it up, just couldn't be bothered

VeX · January 11th, 2009, 08:46 AM

It does make a difference. I am running one jet richer right now for the colder days. When the temperature drops below 55 or so there is a noticeable difference in power. On really warm days there is an obvious lack of power...

Once spring time comes around I aim on stepping back down one jet size, and then back up next fall

noche_caliente · January 11th, 2009, 10:28 AM

I had put a second washer on mine when the temperature was in the 50s, and when I rode at 36* it was still running great... we'll see how it does when it's warmer in the spring, but so far it seems to be just about perfect for me.

headshrink · January 11th, 2009, 01:08 PM

Does temp matter much for FI bikes?
I assume the computer makes all the adjustments.

kkim · January 11th, 2009, 01:23 PM

Quote:

Originally Posted by headshrink

Does temp matter much for FI bikes?
I assume the computer makes all the adjustments.

Are you talking about our bikes? You know ours aren't FI.

FI bikes have temp sensors which relay that info back to the ECU.

headshrink · January 11th, 2009, 05:58 PM

No, I know we don't have FI..... I was just thinking about a 650r at some point and like the idea of not needing to tweak it all the time. Of course there are those power-commander thingies for FI bikes, but that is totally different.

Erin_S · January 11th, 2009, 08:46 PM

Yes, FI will automatically adjust.

Not adjust as well as you can, though. Increasing the fuel map is a lot easier/faster than a jet though... not that you really need to do it anyway.

January 11th, 2009, 02:31 AM	#1
headshrink ninjette.org certified postwhore Name: Bob Location: CA Join Date: Dec 2008 Motorcycle(s): '08 Ninja 250r, '14 CBR500r Posts: A lot.	Rejetting - what time of year? Rejetting will likely be the next thing I do to my bike, if I don't go with the heated jacket first (just ordered gloves). Since there are so many factors in rejetting, I was wondering how much it mattered which season, or what the weather is like, when this work is done. I am in CA and ride 12 months out of the year to commute to work. It is hot in the summer (90's - low 100's) and moderately cold in the winter (30's-50's). I don't know if any of this matters, but then again.... that is my question.

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January 11th, 2009, 02:45 AM	#2
Viper-Byte ninjette.org sage Name: David Location: Wellington, New Zealand Join Date: Dec 2008 Motorcycle(s): 08 Ninja 250R in Green! (Sold) Now 2011 Triumph Daytona 675 SE Posts: 564	From what I believe, the temperature has got apart to play in it as the density of the air and how much gets into the engine is related on the air temp, I THINK the hotter it is, the denser the air is, colder the other way round. You could rejet on a day that is an avg temp over the whole year, this will give a bike with the best power at the mid temps (as this is what you would tune for) or, you could tune (shimming the needles) when the temps get hotter and colder, this will gove you the most power for that temp range, but requires shimming more often. Note, take my advise with a grain of salt, this is what I believe and I am new to this, so I could be wrong, wait for the others to advise.

January 11th, 2009, 03:19 AM	#3
headshrink ninjette.org certified postwhore Name: Bob Location: CA Join Date: Dec 2008 Motorcycle(s): '08 Ninja 250r, '14 CBR500r Posts: A lot.	Thanks. Cold air is denser, but I know what you meant

January 11th, 2009, 04:38 AM	#4
Viper-Byte ninjette.org sage Name: David Location: Wellington, New Zealand Join Date: Dec 2008 Motorcycle(s): 08 Ninja 250R in Green! (Sold) Now 2011 Triumph Daytona 675 SE Posts: 564	NP Well I had a 50/50 chance of getting it right, I guess I should have looked it up, just couldn't be bothered

January 11th, 2009, 08:46 AM	#5
VeX That's me! Name: TJ Location: Ames, IA Join Date: Nov 2008 Motorcycle(s): 2008 Ninja 250r (Tis blue), 2008 CBR600RR Posts: 454	It does make a difference. I am running one jet richer right now for the colder days. When the temperature drops below 55 or so there is a noticeable difference in power. On really warm days there is an obvious lack of power... Once spring time comes around I aim on stepping back down one jet size, and then back up next fall

January 11th, 2009, 10:28 AM	#6
noche_caliente ninjette.org certified postwhore Name: Kim Location: mundo de ensueño Join Date: Nov 2008 Motorcycle(s): '08 250 Posts: A lot.	I had put a second washer on mine when the temperature was in the 50s, and when I rode at 36* it was still running great... we'll see how it does when it's warmer in the spring, but so far it seems to be just about perfect for me.

January 11th, 2009, 01:08 PM	#7
headshrink ninjette.org certified postwhore Name: Bob Location: CA Join Date: Dec 2008 Motorcycle(s): '08 Ninja 250r, '14 CBR500r Posts: A lot.	Does temp matter much for FI bikes? I assume the computer makes all the adjustments.

January 11th, 2009, 05:58 PM	#9
headshrink ninjette.org certified postwhore Name: Bob Location: CA Join Date: Dec 2008 Motorcycle(s): '08 Ninja 250r, '14 CBR500r Posts: A lot.	No, I know we don't have FI..... I was just thinking about a 650r at some point and like the idea of not needing to tweak it all the time. Of course there are those power-commander thingies for FI bikes, but that is totally different.

January 11th, 2009, 08:46 PM	#10
Erin_S ninjette.org member Name: Susan Location: Fredrick, FL Join Date: Jan 2009 Motorcycle(s): Gix Posts: 80	Yes, FI will automatically adjust. Not adjust as well as you can, though. Increasing the fuel map is a lot easier/faster than a jet though... not that you really need to do it anyway.