What size jets??

If I am running shorties from the exhaust collector (2 outlets) and pod filters on my X what size jets should I get?

 

Search & you shall find... (it's still a lottery though! )

 

About 2/3 of the way through this article there is a summary of stock jetting sizes and a set of "formulas" for calculating your starting point for rejetting based on what mods you have: http://xjbikes.com/Forums/viewtopic/t=14692.html

I say starting point because that's all it is; rejetting for pods and a modified exhaust will likely involve some trial and error before you find a combination that works halfway well.

 

You should look into the idea of making some velocity stacks between the PODS and the carbs.

 

I appreciate the help guys. What do you mean by "velocity stacks" between the pods and carbs? And what exactly would I have to do to make them?

 

I appreciate the help guys. What do you mean by "velocity stacks" between the pods and carbs? And what exactly would I have to do to make them?

 

""A velocity stack is a trumpet-shaped device of differing lengths which is fitted to the air entry of an engine's intake system, carburetor or fuel injection.
It is designed to:

• Allow smooth and even entry of air at high velocities into the intake tract with the flow stream adhering to the pipe walls known as laminar flow.
• Modify the dynamic tuning range of the intake tract by functioning as a resonating pipe which can adjust the frequency of pressure pulses based on its length within the tract."" -- Wikipedia

 

Another idea to help get your tuning right, and keep you from burning up your motor -
go to a BIG bike event where they will have a Dyno Trailer, and for $85 or so, + or - , they give you a few dyno pulls with an air/fuel readout.
Do this after you've made your mods and they will show you exactly where you will need to do additional work.

They might show you that you stay safely at 12.5:1 during full throttle acceleration, but lean out dangerously at a steady 75 MPH (for example)

 

Without a Module or anything at-all to reprogram, doing a Dyno run is ... [ in my humble opinion ] ... ill advised.

In order to improve overall performance and make corrections for Fuel Mixtures, ... there needs to be a "Feedback Loop" ... some method of altering the Air-Fuel Mixture that CAN be done with Fuel Injection.

About the only real "Tweak-able" component on XJ-Bikes equipped with its Normally Aspirated ... Hitachi or Mikuni Carbs is Low-speed and Idle.
Once adjusted for Idle and a measure of Supplemental Richness, ... that's all she wrote!

Our Bikes have no Mass Air-Flow sensor.
No method of reprogramming Fuel Supply (Pulse-width).
No Oxygen Sensor.
No Exhaust Gas Analysis.
No Engine Management Software to reprogram.

Any alterations to Enrich or Lean-out the Mixture requires yanking the Carbs for re-jetting.

Its impossible to adjust the performance in any measurable fashion which may be improved upon during the pull.

 

Time-When you say to "make my own" velocity how would I do so? As in, what materials are best to use for this?

 

I saw a set of Stacks on a Honda that were fabricated from Exhaust Pipe.
You need the machine to flair and crimp.

They were made-up to have a Trumpet Intake with a "crimped" section for acceleration and notched necks that allowed for a snug fit before using Hose Clamps to secure them.

Paint or Powder Coat.
Plain looks sorta hillbilly.

 

The easiest way I can think of to "make your own" would be to simply glue/mount/attach the PODS to the factory intake rubber boots.

 

There you go. That's one of the little "secrets" to the stock system: the carb-to-airbox boots are actually velocity stacks on the inside, take a good close look at one. They're not just straight "pipes" by any stretch.

 

That is kind of what I was thinking Time. So if I were to do that, would I mount the pods on very end of the full-length intake boots, or kind of push the boots into the pods as far as they will go (without damaging the filter) and mount them there?

 

The person to ask would be "Streetbrawler" who actually DID this, and here's a link -
http://www.xjbikes.com/Forums/viewtopic/t=28507.html

Me - I'd get a section of PVC plumbing to make an attachment ring maybe 3/4 inch long by 1 1/2 dia. and affix everything with little stainless wood screws and black RTV (or that gasoline-proof flexible sealant) so you could take it apart later if needed. (I would pre-drill everything)
I would think the PODS are larger dia. than the intake rubber.
The PVC would go inside the PODS and add "stiffness" and something to screw into.