pod filters for xj650

anyone know if I need to use bigger jets? i already have the carbs off for cleaning. The pods should be in the mail today should i jet the carbs before i put them back on?

 

Ugh - you're in for a world of tuning fun.

Alas, you haven't provided us with enough information - namely your exhaust - stock or aftermarket? 4-into-2? 4-into-1?

But as a rule, it's almost guaranteed that yes, you're going to have to re-jet the carbs to get them right. Plus you'll need adjustable needles, so getting the jet kits now is probably a good idea.

 

its stock exhaust 4 into 2 but i will be switching to a 4-1 system sometime later this month

 

is there a rule of thumb of how much bigger i should jet? or is it a trial and error game?

 

http://www.hondanighthawks.net/carb09.htm

That should get you started. But you'll likely do a lot of fiddling before you find the perfect jetting for your bike. Good luck!

 

My maxim is running a 4 into 1 Mac and pods . I had to go to 118 mains and 41 idle jets . Had to turn out my air screws a bit too .

 

The Problem:

The Diaphragm Piston Assemblies rise under open Throttle and raise the Needle from within the Emulsion Tube and allow AIR from the Main AIR Jet to bleed into the Emulsion Tubes center orifice to aid in:

1. Breaking-up the Main FUEL Jet's Supply
2. Provide a rush of AIR above the Main Jet Supply to help it be drawn-up and join the Intake Air as the Throttles are opened.

AIR ... becomes the Enemy.

Because so much Air is being drawn-in ... the Off-Idle and Mid-range Mixtures are LEAN.

LEAN is not good.
Lean means the Mixture is going to be too Hot and serious risks to Valves, Seats and the Head result from the Mixture being LEAN. Extreme cases will weld a hole right straight through the top of a Piston Crown.

The need to Re-Jet to offset the Lean Mixture means upping the Main FUEL Jet Size.
Which ...
Only allows for more FUEL to enter the bottom of the Emulsion Tube for feeding into the Engine off-idle and thereafter up the Power Curve.

But, the additional Fuel only serves to balance the Mixture for Off-Idle and the Lower-end of the curve.
The Main Jet's Supply ... at Wide Open Throttle ... needs to be able to deal with the heavy volume of fresh AIR being drawn-in at W-O-T.

Now, there's a transition.
From too much air to not enough ...
So, at this Stage the Main Jetting does not satisfy the Demand and performance nearing Top-end suffers.

Bumping-up another Main Jet size reverses the situation.
Too much FUEL is metered at Off-idle and Mid.
The result is bogging-out at the low-end of the Power Curve.
Wide Open Throttle is satisfied.

Trying to find a >>> FUEL <<< Jet size to satisfy the needs leads to much consternation because one is too Rich and another is too Lean and thehre is not any >>> In Between <<<.

Those of you who are or have removed airboxes and are running Pods need to address the PROBLEM of >>> MAIN AIR <<< along with exchanging FUEL Jets.

Experiment with expanding or reducing the size of the MAIN AIR JET to have an effect upon how much FUEL is drawn-up through the Center Orifice of the Emulsion Tube during:

Just Off-Idle and Mid ... and, ...
W-O-T

Getting the delicate balance of AIR ...

(Increasing the MAIN AIR JET SIZE - or - Porting-out the Metering Holes on the Emulsion Tubes might have a dramatic effect of altering the Fuel Supply
and being able to enjoy the best of both worlds with Pods instead of Stock Airboxes)

Editors Note:

This would be an experimental procedure. I have NEVER done it and do not know of anyone who has.

 

When I installed the K&N jet kits for my bike, I just followed the instructions for Stage 1 -- 118 main jets, and drilled the slides for air.

Mine has the MAC 4-into-1 pipe on it, and a K&N air filter in the stock airbox though, so slightly different situation - but similar.

 

Rick-o-matic,
Well said, I couldn't have explained it better myself. And that's pretty much the reason I left the air box on and just changed the air filter with a Uni-foam mod instead. I haven't heard anyone bragging about the added performance gain after going with pod filters, so that only aids my deicision not to go that route.
It would be nice to get rid of that air box and use the space for something else, but it's just not worth the hassle to me. PD

 

thanks for all the info.. the pods are ordered and i have no regrets....yet. the bike ran poor before the pods anyway... gunked up carbs due to a rusty tank... so i figure i'll try to get stuff done all at once im sure i'll have her ready when the warm weather hits....