Jet kit?

[GQ*]

I'm a rookie, so be gentle.

What exactly is a jet kit and for that matter a power commander? I was looking around online and they just give the basics "maximize performance and power; easy install".

I know that when I was shopping for a used a lot of the bikes had one or both of these add-ons. Are these strictly for a larger bike that I want to get performance out of or would it benefit me to put either on the 2fiddy so I could try to get a lil more out of her?

[kurt]

Jets are the openings within a carburetor that meter the correct amount of fuel to the engine at the proper time. A Power Commander does the same function electronically on a bike that has fuel injection. In either case, changing the engine, intake or exhaust may require these changes.

[GQ*]

Okay, so since the 2fiddy has carbs then I would only want to use a jet kit and not the power commander....but would it be worth it to use on the bike w/o an exhaust upgrade?

[kurt]

Most bikes are jetted lean to pass emissions standards and would beneifit from improved jetting.

[Tim Kreitz]

...but would it be worth it to use on the bike w/o an exhaust upgrade?

Re-jetting the bike without making other changes to how it respirates can have detrimental effects. The term "re-jetting" generally means installing larger jets for increased fuel flow and more power. But if you don't also take proper steps to increase oxygen flow along with it, the result can be a fuel-to-air ratio which is far too rich. This can actually cause things like poor performance and fouled spark plugs.

In short, if you're gonna re-jet, you should probably also increase intake-airflow and exhaust flow through reduced restriction. Otherwise, you're better off leaving your Ninjette as it is.

:thumb:

[Diderich]

bigger jets richen the fuel mixture. Typically, bikes are lean from the factory for emissions purposes. The Ninja 250 is carbureted, so you can forget about the power commander. (At least I think it is still carbureted)

With my GS I could get it to run a little better just fiddling with the air screw and changing the clip on the needle. I never bothered to rejet. I never bothered to add an aftermarket pipe or intake either.


It will probably ride a little smoother with some tweaks to the carburetion. It'd be worth checking out some of the bike specific forums, unless someone else here pipes up. It won't really be any faster though...ever. Well maybe with a turbo...hmmm...now that'd be a hoot.

[Diderich]

man you guys post fast...I can't keep up...

[GQ*]

Yes it is still carbed and no I'm not looking to make it faster, I just wondered if it would be beneficial to try a jet kit in terms of fuel consumption and maybe how smooth she runs in 1st or 2nd gear since right now I hit 3rd by 15 mph lol

[Diderich]

I'm not an expert at all...but I think there are some other things that you can do first, that probably should be done anyways, before a re-jet. Maybe, the air screw...usually hidden behind a "tamperproof" plug. Then maybe shim the needles, if possible.

There are different circuits in the carbs, and jets are only part of the game.

See, for example: This website (http://forums.everything2stroke.com/articles/6407-carb-jetting-101-part-one.html) and This (http://www.motorcyclecarbs.com/carbs101.pdf).

[dukey33]

.. there are some other things that you can do first, that probably should be done anyways, before a re-jet. Maybe, the air screw...usually hidden behind a "tamperproof" plug. Then maybe shim the needles, if possible.


Yes. Check the carb balance (often not set well from the factory, nor does the dealer always check it before sending it out the door), adjust the mixture screws and shimming the needles (because most no longer have adjustable clips) can go a long ways to improving baseline rideablility.

[GQ*]

I'm not an expert at all...but I think there are some other things that you can do first, that probably should be done anyways, before a re-jet. Maybe, the air screw...usually hidden behind a "tamperproof" plug. Then maybe shim the needles, if possible.

There are different circuits in the carbs, and jets are only part of the game.

See, for example: This website (http://forums.everything2stroke.com/articles/6407-carb-jetting-101-part-one.html) and This (http://www.motorcyclecarbs.com/carbs101.pdf).

Thanks for the sites...i just gave them a once over and after being a little confused I think I have the basics (loosen screw to richen mixture).

I also found this shimming (http://www.captainjakes.com/w650/shimming/shimming.shtml)...has anyone done this that can tell me how much this helped and how long it took? This looks like something I might try if it's beneficial and not just something to say I did....although being able to say I shimmed my needle sounds cool! :lol2:

[dukey33]

If you're willing to tinker with your bike (still under warranty?), do it.
It broadened the mid-range substantially on my Vulcan 500. But I will say I did lose a bit of fuel economy. About 10%. Maybe it's just me enjoying the extra torque.:rider:

[GQ*]

Good point, I almost lost sight of the warranty. I guess I will just enjoy her as she is until the warranty runs out. BTW any thoughts on buying an ext warranty? The dealer is pushing a 5yr/unlimited mileage warranty for $500, but I've been holding out.

[Diderich]

do NOT get the extended warranty. These bikes are not expensive to work on, and largely, if you have any mind to tinker at all, you can do it yourself. Plus, these 250s and 500s are pretty much bomb proof and will run forever. Any lemons will be likely discovered during the normal warranty. Spend that $500 on gear, consider it a $500 skin and bones warranty.

Synching the carbs will make it run better (if they are out of synch) and will not void the warranty.

[GQ*]

How do I know if I need to synch them versus tweak them.

[Diderich]

Carb synch tool.

Basically, you connect something up to the vacuum port on each carburetor and compare the vacuum reading. They should be equal. If not, there is a screw between the carbs that adjusts the butterfly (if I recall correctly..been a while since I had carbs).

Adjust until each cylinder reads the same vacuum.

Usually a tool can be made by making a big 'U' in some clear tubing. Put a little bit of water in the 'U' and connect the free ends to the vacuum ports. adjust until the water level is even in the 'U'.

Or there are plenty you can buy...

[Tim Kreitz]

How do I know if I need to synch them versus tweak them.

Use a mercury manometer. Here we are synching my ZX7R:

http://www.youtube.com/v/KefbfV_rJnc&hl=en