XJ650 carb tuning with the dreaded "pods"

Sorry for the multiple posts. Bad computer mojo back here at work.

Maybe big brudder is monitoring my i'net usage.

 

I have an '83 XJ900RK Seca-900.

I don't mind it when others disagree with me. That's the whole purpose of exchanging ideas and information in a Forum Setting.

People disagree with me on Fuel, Batteries, Brushes, Head-torque-check while the Head is still warm, Tires and Carb Mods and Pods.

I'm glad there's a recipe for Jetting to make Pods run the bike well. Do I think the bike will run as well with Pods.
No.
I don't. But, I'm a little too Anal about making Mods from Stock set-up's, anyway.
(I almost bought a OEM Style Fuse Panel to perserve the "Look" until I convinced myself it was just the same one giving me so much trouble.

I think there's a difference between a Velocity Stack and a Venturi Opening, so I standby my position of Turbulence having an effect on the Intake.

 

That's fine Rick, I've always known your stand on Mods from original. :lol:

But the key bit to remember is CV carbs have been used on many different makes and models of bikes and each has a different setup for airbox and intake.

But the best option is to take a look at the XJ550 intakes. There is very little(if any) taper from the airbox to the carbs so the venturi/velocity effect is minimal.

The other key factor in our old XJ's is they were designed thirty years ago. Long before Computer Aided Design came along to help with aerodynamic design of the airflow.

I'm a firm beleiver that the airbox was the last piece they built and just crammed it into the available space that was left over with little regard to airflow. I mean, If you were to design a performance bike, would you stick the air intake in a pretty much enclosed space under the seat??? Facing backwards from the airflow??


I think the best story I have heard relating to that intake is the guy who loved his bike so much he used to carry a rag around with him to polish it up whenever he got dirt on it. While troubleshooting a problem with no power above 2000 revs, it was discovered where he kept that rag.

Yep, you guessed it. In that little cavity behind the air intake. :lol:

 

I'm not ready ti cross-over to "The Dark Side", yet.

But ... I do have a Colortune Plug. And I did get a set of MotionPro carb Sticks.

So, at least I have stopped "Tweaking by Sound and Feel" and Syncing by using a Single Vacuum Gauge.

I guess I'm too old to fool-around with all that re-jetting when I know I can get a stock bike running pretty good when I put my mind to it.

I'm sure having a bunch of fun playing Dr. Tweak with the 750 Max.
I'm striving for perfection in my minds eye ...
Looking for a Tweak between Acceleration and Smooth.
I'll find it.
I did a little Tweak to 'er, today ... that didn't move the Screws more than the width of a Dime. Maybe half that.

So, I'm not quite too Lean and Not too Rich to notice.
But, the Screws are oiled nice and its fun to play with my bike!

 

I dont own an xj, but I do own a GS I am modding. I stumbled on this thread because of carb issues with my vm26's.. Will be trying some of the suggestions made on this thread to get me pointed in the right direction. Here is a few pix of my bike and my custom intakes for anyone interested.

 

Both of these bikes look nice. I remember a member on this site attached the pod filters to the end of his carb to airbox boots creating (velocity stacked pods). This seemed to help his situation, I believe it was Streetbrawler. Look him up and PM him.
You could also trash the CV carbs and replace them with some roundslide carbs or go the EFI route.

 

I suppose its too late to ask you to resize the pictures.

Those Carbs are A LOT more "Pod friendly".

I'm looking for a set of those to see if they can be adapted to fit a 750 Maxim.

(If you can reduce the size of the photos, ... that would be nice.)

 

Thanks for the responses and I'll resize.

 

People disagree with me on Fuel, Batteries, Brushes, Head-torque-check while the Head is still warm, Tires and Carb Mods and Pods.[quote RCM]

You forgot the starter clutch shortcut. BTW, still waiting for your tec' report. Wiz.

 

Just a note on tuning, after checking the valve lash, make sure you have the correct tension on the cam chain, as this can effect valve timing.

 

*Cough* beercan mod, it creates velocity, works great and looks cool *cough*
Seriously, as much time and headache as people have been putting into the pod filter crap....this is really the only way.

 

The only way is to put the stock airbox rubbers in the pod instead of the rubber that comes in the pod

 

I know this post is old as hell, but have you guys come up with a bullet proof method on which exact size of jets to use?

 

I'll go out on a limb and say.........no, but I'm sure someone on here will say I'm wrong!

 

Well I've seen lots of talk of guys doing it, but no step by step method with jet sizing involved :/

 

There is a reason for that, and it's not because there is some secret guild initiation you have to go through before the secret will be divulged.
The only way to figure out what jets work the bet for your bike, in your location, is for you to do that work. There are plenty of tthreads with recommendations that can get you in the ballpark, but none that will be perfect (for reasons that I think you already know).

 

first there are many factors involved to get bullet proof. pod brand to start and motor condition this is why it is said get it running correctly stock then go modified
you do need the velocity stack between carb and pod.

and then this is what you have to do
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

so start by buying a pocket full of main jets and start changing them out do your plug chop change jet do plug chop......


The Information Overload Hour gives you a place to start depending on what mods you have.
all you will do is move the flat spot on your throttle around to where it bothers you the least which depends on your riding style.

sounds like to much effort for the look of pods.
dont you think yamaha would have done pods instead of air box if it made a better bike???????????/

 

it's totally worth reverting back to the stock airbox. I just purchased an 82 xj650 seca with cheap ebay Pods. one of the first purchases I did was to buy an original airbox that I will be re-installing this weekend. Another issue I have with the pods is the weight of them cannot be supported by the intake boots. I hear them bouncing around while riding. Not a comforting sound at all.

 

@k-moe posted this in another thread
it is quite an explanation of the air box and its function

"Pods really aren't for max airflow though. They look like they should flow more air, but in practice they don't always. The XJ airbox is realtively restrictive, but the advantages from the waveforms generated in the airbox overcome that restriction. In addition to providing the airflow necessary to allow the carb slides to move properly (and quiet intake noise), the airbox also uses the resonance developed from the "blowback" of the cylinders (a consequence of valve overlap) to force-feed a little more air through the one carb that is working on the intake stroke. With individual filters that free-supercharger (as Kevin Cameron calls it) deos not exist.
Have a look at what a modern airbox looks like on a sportsbike. They are huge, and have many different shapes within to further tune the resonance for maximum effect in the midrange (exactly where we see pods cause a flat-spot in our XJs). This is done even on (most) fuel injected race bikes, where one would think that pods would have an advantage without causing any fueling issues. "

my comment
so if you do not understand this statement you should not even be thinking about podding.