Tuning carbs for altitude

[PsychoNinja]

This winter and/or spring I would like to ensure that my Ninja is tuned properly for the altitude that I live at. I have been searching online for any manuals or tech specs regarding tuning our carbs for altitude, but I cannot find anything. Any thoughts to help a newbie out?

I live at approximately 4400-4500 ft above sea level.

Any help would be greatly appreciated!

[spooph]

any mods to the intake/exhaust?

[PsychoNinja]

No mods right now.

I do plan on K&N air filter, Yoshi Full Exhaust, and Stage 2 Jet Kit, but that's not gonna happen anytime soon.

It does appear that my Ninjette is running rich. I checked the oil fill and it smells like there may be fuel in the oil. I plan on checking my plugs too to see if it confirms that the engine is running rich as well.

[spooph]

Yup, I was gonna say, that you'd maybe want to go to 96 main jet's, raise the needls 1-2 shims, and go to 2-turns out on the air/fuel mixture screw (if the plugs been drilled out). But that's about all you'd need to do... You could try 94 main jets, but that might be a touch too lean.....

I'm at 5,000 feet, and these aren't just my numbers. They have been verified by most 250 racers here...

[tjkamper]

Definitely. Stock jets or 96s. You could put one or two shims on the needles and see what happens. About two turns on the idle mixture screws. That is a good baseline. Then play with it from there.

If you do the K&N then you are looking at having to go a lot richer all the way around. you'll probably be fine with the stock pilot jets even with all those mods at that altitude.

My current setup with the 40s pilot jets is great at 2000 feet, but when I ride to utah, It is too rich and bogs down and almost dies in stop and go traffic.

[spooph]

My stock idle jets were 98's, not sure why that is, but keep an eye on that Psycho...

If you want to get really anal and crazy accurate, you can get yourself a set of jet drills, aka, jewelry drills - 81-60 guage kits are cheap. 2 drill sizes usually equal 1 jump in jet sizes, so you can tune very accurately for this.

Unfortunately (and this is why i want FI so bad), you can tune a carbed bike very accurately for one day, but it will be off again the next... I find having 2 sets of jets - summer and winter is a good way to go. Our fall and spring isn't long enough, nor consistent enough to warrant 4 sets of jets....

For the winter, you can usually jump up one size in jets, all around. Your needle and air/fuel mixture setting might vary a little, but probably not by much.

Keep in mind, I'm saying this assuming this is for general commuting/street riding where you're not really going to notice a massive difference if the jets are off just a bit.. On the track, you might.... On the other hand, the ninjette engine is a very docile power plant, especially in stock trim, which makes it more difficult to notice small effective changes....

[PsychoNinja]

Thanks for the suggestions spooph and tjkamper

Since this is my first carbed vehicle that I will be tuning, I have another question. Is adding shims to the needles going to make the AFR leaner or richer? Does turning out the needle increase airflow or fuel flow to the carb?

[kkim]

what is your end goal... to meet emissions standards for your location or performance?

[PsychoNinja]

Originally Posted by kkim

what is your end goal... to meet emissions standards for your location or performance?

Mostly to optimize performance and efficiency for where I live.

[kkim]

Then I would recommend you make your intake and exhaust upgrades, buy a jet kit and start tuning.

[JMcDonald]

Raising the needles leans the lower-end and midrange mixture. I think they are making the asdumption that while a leaner main jet might be necessary for the top end, the midrange might be too lean without shimming.
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[kkim]

Originally Posted by JMcDonald

Raising the needles RICHENS the lower-end and midrange mixture. I think they are making the asdumption that while a leaner main jet might be necessary for the top end, the midrange might be too lean without shimming.
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corrected that for ya.

[JMcDonald]

Gah i was thinking about that a little bit ago--"wait did I said it leans the mixture?" Was too busy to check. Heh thanks for that correction :P . Youd think with carb tuning so fresh on my mind Id get the little things right lol.
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[tjkamper]

Originally Posted by spooph

My stock idle jets were 98's, not sure why that is, but keep an eye on that Psycho...

From the Factory the Mains are 98s and the Pilot (slow jets) Jets are 38s.

[rwheelz]

Hmmm I also live near this elevation, and just ordered the parts to do all of this work over the holidays on my wife's '09. I live just shy of 4000 feet, so I will let you know how it works out for us (full exhaust, K&N pod, FP jet kit).

[JMcDonald]

Great! When you finalize it, be sure to post up your results in the jetting database!
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[PsychoNinja]

Thanks for the input everyone!

Originally Posted by rwheelz

Hmmm I also live near this elevation, and just ordered the parts to do all of this work over the holidays on my wife's '09. I live just shy of 4000 feet, so I will let you know how it works out for us (full exhaust, K&N pod, FP jet kit).

Looking forward to your results!

[kkim]

have you checked the jetting database for people that are in a similar elevation?

http://www.ninjette.org/forums/showthread.php?t=10208

[PsychoNinja]

Yeah I checked the jetting database. I only saw one person in the same elevation range as me. I will go over what he did as well when I am ready to start making adjustments on my carbs.

[Bueller999]

Originally Posted by kkim

have you checked the jetting database for people that are in a similar elevation?

http://www.ninjette.org/forums/showthread.php?t=10208

All kinds of sea level, didn't see much for 10k'

[kkim]

Originally Posted by Bueller999

All kinds of sea level, didn't see much for 10k'

yep, not many at 10K. if you've rejetted yours, please add your finding to the database.

[Bueller999]

I have been riding it w/stock jetting (as I just found out) since I traded for it. I even tracked it and raced it at the end of the season like that.
Now it will be a race bike but it is a spec class that requires a stock airbox with snorkel in place. So I will be playing with the jetting but I doubt my numbers will do street bikes any good.

[headshrink]

Originally Posted by PsychoNinja

I live at approximately 4400-4500 ft above sea level.

Along for the ride.....

That is approx. the altitude I start noticing a difference. The difference is significant at and above 5,000' ASL. I live at ~ 500, so I'm not tunning to high altitudes, but trips to Tahoe have given me these numbers (the pass is a bear at ~6,500' ASL). This was with a stock pipe & shimmed needles (at the time). I'm looking forward to the snow melting so I can try it with my Area P, re-jet, etc. I find it may actually help diagnosing tunning since it exaggerates everything at the same time... at least I think so.