Going back to stock airbox/exhaust from 4-1 and pods. Jetting?

[TheRadBaron]

Hey guys, I haven't been on here for a while but I'm getting back at it.  I've assembled most of what I need so I'll be putting the wrench to my '84 again soon.
I've been riding the bike with a V&H 4-1 exhaust and the Uni twin pods.  The slight midrange burble/flat spot from the 4-1 always bugged me so I traded it for a good, original exhaust.  While I'm at it I'm going to put the stock airbox back on.  I rarely ride the bike at the upper RPM range and I'd be happier with a good, clean, torque curve.
So I figure that the obvious choice would be to go back to the factory jetting, but I have a few slight changes that might make a difference.  Plus, I know that a lot of '80s bikes were a bit lean from the factory and can benefit from slightly richer jetting.  Here's what I'm working with.
-'84 FJ1100 with stock motor
-New FJ1200 carbs bought from RPM
-Stock exhaust system
-Stock airbox with Uni filter (possible a bit more flow than factory if Uni is to be believed)

My main concern is that the 1200 carbs have slightly different brass than the original 1100 units and I'm not sure if different jetting is in order.  Any help would be appreciated.  I know that this has probably been covered before and I apologize.  I have very slow internet and searching for this type of thing can be appallingly slow.  Thanks.

[FJ_Hooligan]

Keep the UNI pods.  It's not about airflow. 

Your bike may have been jetted for the 4:1, but I wonder if the needles were shimmed?

Does it have a carb kit with adjustable neeldes?

[TheRadBaron]

The carbs do have adjustable needles.  I adjusted the pilots, mains, needles, and air compensator jets based on the recommendations of the experts here, then fine-tuned it myself.  I'm pretty good at jetting but I understand that the midrange problem is common to the 4-1 setup and hard to totally tune away on these bikes. 
Why do you say keep the pods?  In my experience a 4-cylinder bike will almost always run more cleanly with an airbox over pod filters.  I know pods make carb access a lot easier, though.  Will the FJ truly run better with the Uni dual pods?  Again, I'd like the cleanest power delivery, not necessarily the highest peak HP.

[FJ_Hooligan]

Lots of people have converted to the pods without experiencing any fueling problems.  It's just a matter of making up for the difference in intake restriction between pods and an airbox.  You don't do that with jets, it requires needle tuning. 

You've got adjustable needles.  You should be able to make the pods every bit as good as an airbox. 

I would agree that the biggest contributor to fueling issues in the midrange is the pipe.  I'm a BIG proponent of stock exhaust.

[TheRadBaron]

I think I'm going to put the airbox back on it.  I like the idea that the airbox provides a fixed volume of relatively still air for the carbs to draw from.  It seems to me that this would have to make for more accurate fueling.  I know that FJs are not too sensitive to jetting compared to a lot of other 4-cylinder bikes but pods really can play hell with other machines, even to a good tuner.  I'm sure that they can indeed be made to work well on an FJ but I like the idea of the airbox.
Now I just need to get a jetting baseline nailed down.

[FJ_Hooligan]

I like the idea that the airbox provides a fixed volume of relatively still air for the carbs to draw from. 

Really?  There's nothing "still" about the air in the airbox when the engine is running.  It's constantly flowing.  What the airbox does is add an intake restriction.  This restriction causes the air flow to speed up which results in a higher vacuum in the carb throat and a resulting higher jet needle position.  When you remove the airbox and install pods, the restriction is reduced, the air velocity in the carb throat is slower thus the needle is in a lower (leaner) position.  To compensate for this you simply need to raise the needle to get it back to it's original position.  This is all well documented in the files section.

One thing an airbox can do is provide a resonance for the back pulse caused by the intake valve closing.  At a certain RPM, this pulse will reflect back through the carb and provide a slight ram air effect to the intake flow.

So there's some science, worth every penny you paid for it.....

[racerrad8]

The carbs do have adjustable needles.  I adjusted the pilots, mains, needles, and air compensator jets based on the recommendations of the experts here, then fine-tuned it myself. 

What adjustable needles did you put in the new carbs?
What is you current jetting; pilot, air bleed, main jet and needle position?
What is the current float level?

Randy - RPM

[TheRadBaron]

It's been a long time since I originally set up this bike and I've fiddled with a lot of carbs since then.  I searched for some of my old threads from back then and here's what I came up with.
-The new carbs were from an XJR1250, not an FJ1200 as I originally stated
-I don't remember the exact specifics on the needles but I bought them from RPM.  I believe they're the same as the FJ1200 needles but have the adjustable clip position.  I have the clips in the #3 position.
-125 main jets
-37.5 pilot jets
-Pilot air screw 2 turns out
-140 air correction jets
-Float height was checked when I got the new XJR carbs and my old post said that it was spot on at 22mm or so.

[Fj.itis]

Yeah ive noticed that slight flat spot at 4000 to 4500 rpm, little bit annoying but makes up for it when you hit 6000 rpm. Ive got 1100 4 into 1, pods with 40 pilots, i think stock needle but its shimmed, 3.5 turns out on mixture and 112.5 mains which could be a bit larger.

[Sir Denis Eton-Hogg]

My 1993 has the stock pipes, air box removed and carbs fitted with some of those twin foam uni air filters.

I bought it a month back, it had an idling issue and thought I was in for a fun ride getting the carbs set up - especially as it was jetted in San Diego and we are at 5,000 ft here in Colorado.

However, after replacing he pilots and adjusting the mixture screws, the bike runs great, starts easily, idles nicely, pulls all the way in every gear and has plenty of that lovely midrange overtaking torque. Turns in about 42 mpg on my commute, plugs look textbook.

Carbs settings are:

42.5 pilot jet
Mixture screw 3.5 turns out
Factory needles with clip in middle (3rd) position.
132.5 main jets.

[FJmonkey]

Stock pipes and 132.5 main jets? Seems really rich.... And your first first post? We are a friendly bunch and like to know our members so introductions is a minor requirement, for a membership with free admission. Tell us more about your FJ and your story...

[FJ_Hooligan]

My thoughts also Monkey.  But that main doesn't come into play unless the throttle is pinned at WFO.  Not sure about anyone else, but that's rare on my FJ.

Also, factory needles only have ONE clip groove.  Multiple grooves indicate an aftermarket needle or non-US spec bike.

[Sir Denis Eton-Hogg]

Stock pipes and 132.5 main jets? Seems really rich.... And your first first post? We are a friendly bunch and like to know our members so introductions is a minor requirement, for a membership with free admission. Tell us more about your FJ and your story...

My story? - I bought an FJ about a month ago, probably the 12 or 13th one I've had.

When I say factory needles, I mean from these guys,  http://www.factorypro.com/ , not stock from the factory in Japan.

Yes, I thought it would be really rich too but I don't think it is, will stick on a dyno in the next couple of months.

[Sir Denis Eton-Hogg]

Stock pipes and 132.5 main jets? Seems really rich.... And your first first post? We are a friendly bunch and like to know our members so introductions is a minor requirement, for a membership with free admission. Tell us more about your FJ and your story...

My story? - I bought an FJ about a month ago, probably the 12 or 13th one I've had.

When I say factory needles, I mean from these guys,  http://www.factorypro.com/ , not stock from the factory in Japan.

Yes, I thought it would be really rich too but I don't think it is, will stick on a dyno in the next couple of months.

Just checked, it's my 11th FJ.