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Rejetting due to moving to Colorado.

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Gr1mreaper

Joined
Mar 2, 2022
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Location
Fort Collins, CO
So, help, please. I moved to Colorado from Texas, elevation change being 480 something to 5000.
I need to rejet my 2011 Kawasaki Ninja 250r, I haven't the slightest clue where to begin.
I've done some light work on the carb before to clean it and everything so I know how to take it out of the bike, but from there I don't even know where to start
 
Owners manual or service manual should make it easy. Probably has a chart for different temps and altitude.
 
Bryan L said:
Does the bike have aftermarket jet kit ? Stock air filter , and exhaust ?
Click to expand...
it has an aftermarket slip-on and a K&N air filter. As far as the jet kit goes idk, the former owner never mentioned it and when I took it apart when I got it I was too dumb to know the difference.
 
Gr1mreaper said:
Is there a good place to find one of these?
Click to expand...
Links to download pdf of owners & service manual
Owners
Service
https://encontrapeca.com.br/catalogos/manual_servico_KAWASAKI NINJA 250R.pdf

I did a quick look at manuals & did not see any info related to carb adjustments for higher altitude (service manual shows standard jetting in section 3.8.
link to Ninja forum that I previously posted has this info,so you may want to review those posts that are listed for Jetting for Altitude:
1702167965650.png
 
Have you already tested it at 5K? My bikes have not had a problem until much higher elevation but I never push them.
 
Gr1mreaper said:
it has an aftermarket slip-on and a K&N air filter..
Click to expand...
It should have been rejetted to accommodate those add-ons. If it ran well at 500’, it probably was done.
That’s too bad as the stock jets would likely have been ok with the altitude change. The factory goes lean to start with so going to thin air usually works ok. If the PO gave you the stock jets, put those back in for a good starting point.
 
Bigger displacement is more forgiving at altitude. When you start off with 50+ hp then losing 20% in thin air is tolerable. With a 250 you're starting out at minimal hp. Losing any will be very noticeable. Any of the rejet vendors will have the info and items you need. Dynojet is one of several. Rejetting is easy. Basically takes a small flat screwdriver and a few minutes. You already know how to remove the carb which is usually the most difficult part. You'll be unscrewing a couple of jets and probably replacing the needle. This is a time to lay out a big clean towel to work on in a well lighted area and put on your glasses. Be especially careful with the needle clip and it wouldn't hurt to get a couple of spares while you have it in hand. The rejet kit will have a chart showing which jets and needle settings to use at a particular range of altitude (like from 5-9k'). Go with their recommendations and you'll likely be happy with the results.

*When you go above 10.5k' you're going to lose hp regardless. Your fuel mix may be spot on but when the O2 ain't there...
 
Last edited:
_RG_ said:
Bigger displacement is more forgiving at altitude. When you start off with 50+ hp then losing 20% in thin air is tolerable. With a 250 you're starting out at minimal hp. Losing any will be very noticeable. Any of the rejet vendors will have the info and items you need. Dynojet is one of several. Rejetting is easy. Basically takes a small flat screwdriver and a few minutes. You already know how to remove the carb which is usually the most difficult part. You'll be unscrewing a couple of jets and probably replacing the needle. This is a time to lay out a big clean towel to work on in a well lighted area and put on your glasses. Be especially careful with the needle clip and it wouldn't hurt to get a couple of spares while you have it in hand. The rejet kit will have a chart showing which jets and needle settings to use at a particular range of altitude (like from 5-9k'). Go with their recommendations and you'll likely be happy with the results.

*When you go above 10.5k' you're going to lose hp regardless. Your fuel mix may be spot on but when the O2 ain't there...
Click to expand...
Very excellent advice especially about the spare needle clips. :thumb:
 
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