Need to rejet Ninja 500R - got some questions

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jfeaz · #1 Unread post by **jfeaz** » Thu Jun 12, 2008 10:48 am

Hey guys,

I bought my Ninja 500R on eBay and picked it up in Las Vegas. Rode it around in socal for a while and it was great. When I brought it up to my home in Colorado (7500 ft), i noticed a severe power loss and slightly higher fuel consumption.

So I concluded that it's time to lean it out. I want to do the work myself, but I have some questions.

1) What do I have to buy? Is it cheaper to get parts separately or to buy a kit?

2) Is it just a matter of taking out the carbs, taking them apart, and putting in the new needles, or do I have to do other stuff too, like adjust the fuel level or mess with the mixture screw?

3) Will it turn out to be a nickel-and-dime money pit?

4) Which jets have to be replaced? There are main jets, pilot jets, air jets, starter jets, I'm confused!

4) What size jets do I need? According to the Clymer manual, the factory specs are:

Main jet: 130
Main air jet: 100
Jet needle: N36N
Pilot jet: 35
Pilot air jet: 130
Starter jet: 50

Thanks for any help!

HYPERR · #2 Unread post by **HYPERR** » Thu Jun 12, 2008 1:41 pm

Do you know if the original owner changed the jets on the bike? Most bikes run lean out of the box at sea level so a lot of owners at sea level re-jet the main and sometimes the pilot.

It's usually cheaper to buy the jets, needle, etc separately compared to kits like dynojet.

What does you airbox look like? Do you have a removable snorkel? If so, taking that out will flow more air into the airfilter leaning out the bike quite a bit. It will certainly help and it won't cost you a dime.

jfeaz · #3 Unread post by **jfeaz** » Thu Jun 12, 2008 2:33 pm

really? i've never heard of that but i'll have to check it out. i like the part where it doesn't cost me a dime.

The original owner did not change the jets. They left it stock.

HYPERR · #4 Unread post by **HYPERR** » Thu Jun 12, 2008 2:47 pm

jfeaz wrote:really? i've never heard of that but i'll have to check it out. i like the part where it doesn't cost me a dime.

The original owner did not change the jets. They left it stock.

Opening up the airbox and putting on an aftermarket exhaust is a very common performance upgrade. The former sucks in more air and the latter gets rid of the exhaust quicker, thus increasing performance.
However, in order to do those mods on a carburated bike, one must rejet to a bigger main and pilot as those two mods make the bike run lean. However since you are running rich already, you can do the airbox mod right away.

A lot of bikes have a snorkel with almost a slit for an opening. By removing that, you will get a lot more air into it. If you have the round snorkel, you won't really change the flow that much by removing it. In those cases, the popular mod is to drill a similar hole next to it or remove the lid altogether as long as it is done in a way it does not let unfiltered air in.

I would do a google search by typing in something like Ninja 500 airbox mods or somthing and see what comes up.

jfeaz · #5 Unread post by **jfeaz** » Thu Jun 12, 2008 3:37 pm

awesome, i'll look into that.

Do you think the amount of extra airflow from doing that mod will balance the mixture enough or would i still need to rejet?

i'm also interested in saving fuel.

HYPERR · #6 Unread post by **HYPERR** » Fri Jun 13, 2008 5:39 am

jfeaz wrote:
Do you think the amount of extra airflow from doing that mod will balance the mixture enough or would i still need to rejet?

Hard to say, but it will definitely get you closer to the proper mixture.

jfeaz · #7 Unread post by **jfeaz** » Fri Jun 13, 2008 7:02 am

I did some research on it, and it definitely seems like a good place to start. I'll give it a shot and see if it makes a difference.

jfeaz · #8 Unread post by **jfeaz** » Sun Jun 15, 2008 8:27 am

I did the airbox mod today...it definitely took the flat spot between 4-5,000 RPM out, and it made the bike a lot noisier, but it still doesn't seem to have any more power.

How can I tell if I made the mixture too lean, or if it's still not lean enough?

HYPERR · #9 Unread post by **HYPERR** » Sun Jun 15, 2008 8:42 am

jfeaz wrote:I did the airbox mod today...it definitely took the flat spot between 4-5,000 RPM out, and it made the bike a lot noisier, but it still doesn't seem to have any more power.

How can I tell if I made the mixture too lean, or if it's still not lean enough?

You can easily tell by looking at the plugs.

I'm assuming you never pulled the plugs. Since you were running rich for a while, the pugs need to be either cleaned or replaced with fresh ones.
Once that's done, you can ride around for a little while and then pull the plugs to check out the mixture condition.

jfeaz · #10 Unread post by **jfeaz** » Sun Jun 15, 2008 11:05 am

I just pulled the plugs (without having done much riding with the airbox mod) and they are brownish-copper colored with no visible deposits.

Would this indicate the mixture was too rich before?

So the next step would be to put them back in and ride around for a while and see what the airbox mod did to the mixture, right?