No More Pods!

Hey everybody.
I've been away for awhile, but i'm finally back to working on my Maxim. (I'm refusing to let it die...) I've finally gotten a new stock airbox and pitched the pod filters into the can.

I'm having trouble getting the bike to idle though.

It'll run (at 3000rpms) until I touch the throttle. I can't back the main carb screw down to 1100rpms, without it dying. I can't tell if the bike's getting too much fuel, or not enough.

Also:

The Main Jets (from 1-4) are 118, 120, 120, 118.

The Pilot jets are all 40.

With a stock airbox...do I now need to down the Mains to 110?


Again,
Thanks so much for the advice.

_Wayne

 

With a stock airbox and stock air filter, the above combination should be okay, you may end up having to go up to a #112 main fuel.

You should also have a look at the main and pilot AIR jets up top and make sure that they are correct for an XJ650---they should be #205 Pilot Air and #50 Main Air jet.

And hope that no one drilled out the air bleed holes in the vacuum piston.......

 

Do you mean that what I have in my bike right now (118's and 120's) should be okay....or when I do put 110's in it...then it'll be okay?

 

For a stock airbox, with a stock air filter element, and an aftermarket exhaust system, you should be able to get by with the stock fuel jet configuration (#110 main and #40 pilot), or you may have to go up just slightly on the main fuel jet to a #112.

Running #118/#120 main fuel jets in the above configuration would probably result in a rich mixture.

Here's the commonly used formula for calculating fuel jet sizes:

I've never used pods on any of my bikes, they just seem like way too much trouble to me! BUT, here is the "standard" re-jetting recommendations from people who fool around with them....although, please be aware that every situation is different, and you should expect to go through some amount of trial and error (and frustration!) before you get it as close to right as is possible.

By the way, the most important part of the information below is in the section titled "PRECAUTIONS"!:

So here is the info regarding jetting that I found:


MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

+4 main fuel jet sizes for 4-into-1 exhaust

+4 main jet sizes for no muffler (open headers)


Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

+2 main fuel jet size for drilling holes in the airbox

+4 main fuel jet sizes for individual pod filters (no airbox)


Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 per every 2000' above sea level.

- Under a mismatch condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.


PILOT FUEL JET SIZES CHANGES NEEDED PER TYPICAL MODIFICATION:

Pilot fuel jet size changes are related only to the change in main fuel jet sizes according to the main fuel jet size formula described above. Note that this pilot fuel jet rule is for the main fuel jet size change BEFORE any main fuel jet altitude compensation is factored in:

Increase the pilot fuel jet size +1 for every +3 main fuel jet size increases.

Additional changes:

- Decrease pilot fuel jet size by 1 for every 6000' above sea level.



PRECAUTIONS:

- Make sure your carbs are in perfect working order before making jet changes....meaning fully cleaned internally and rebuilt.

- Check plug color often and adjust as needed, 2 main fuel jet sizes at a time and 1 pilot fuel jet size at a time. Bright white plug insulators are a sign of an overly lean fuel mixture condition and WILL cause damage to your engine over time, up to and including engine seizure!

- Synch the carbs after each jet change.

- Make sure the floats are set correctly

- Seriously consider purchasing a Colortune Plug Tuning kit.

- You may find it necessary to make changes to the size or shimming of the main jet needle. There are no guidelines on what or how to do these changes, this is true trial-and-error tuning!




EXAMPLE:

Stock Carb Settings:
#120 Main Fuel Jet
#40 Pilot Fuel Jet
Y-13 Needle

MAIN FUEL JET SIZE CALCULATIONS:

Changes made:

Exhaust:
4 into 1 with Supertrapp = +4 Sizes Main Fuel Jet

Intake:
K&N Pod Filters = +4 sizes Main Fuel Jet
----------------------------
Equals: +8 main fuel jet sizes baseline
Subtract: -2 main fuel jet size per formula above
----------------------------
Equals: +6 main fuel jet sizes due to modifications, thus:

Stock main fuel jet size is: #120
+ 6 additional sizes
= a #126 main fuel jet size
---------------------------
Subtract: -2 main fuel jet sizes for Altitude of 2500' Average

= #126 calculated from above
-2 jet sizes for altitude adjustment

= a #124 main fuel jet size.


PILOT FUEL JET SIZE CALCULATIONS:

The formula is: +1 pilot jet size increase for every +3 main jet sizes increased.

Stock pilot fuel jet size is: #40
+ 2 additional jet sizes (since we went up +6 main fuel jet sizes before the altitude compensation was factored in)

= a #42 pilot fuel jet size.

Note that no altitude compensation is needed on the pilot fuel jet since our elevation is less than 6000' asl.


------------------------------

RESULT:

A #124 Main and #42 Pilot is A GOOD STARTING POINT.

******************************************************

 

I assume that will apply to a XJ750?

Thanks for the chart! Very helpfull.

 

Should apply to all model carbs, I assume....remember, I didn't come up wioth those numbers, I just "translated" it from another poster to make it more readable. But from all that I've read, it seems to be okay AS A STARTING POINT.

The holy grail for carb tuning can be found here:

http://www.factorypro.com/