DJ jetting question!

[Tor-King]

So, I am in the process of putting my bike to stock, (carbs and exhaust).  After taking apart the carbs, it became apparent that a DJ kit was installed as an aftermarket exhaust was also put on at the same time.  I am running the original airbox.  The pilot jet looks to be original 37.5 and the main jet appears to have "112" inscribed on top.  The slide needle is at the 2nd position and the mixture screw is at 3 turns out.  Here are the questions:

1.  Is there a difference between a DJ112 jet and a 112.5 Mikuni (stock for '93)?

2.  Can I leave the DJ needle in?  Is there a difference?  Should I keep it at position 2?

3.  Should the emulsion tubes be changed--would it have been a DJ part in the kit?

4.  Having the mixture screw out at 3 turns appears to be close to original setting.  Should that be adjusted?

I know there are quite a few questions, but I want to do things right and I am learning a whole lot along the way!

Thanks,
Dean

[RichBaker]

Yes.... Nice comparing the various jets.

http://www.fjowners.com/index.php?topic=1973.0

[Tor-King]

Thanks for that link, Rich!

I am however, more confused as it looks like a DJ112 is equivalent to a Mikuni 105?  Is that now making it even leaner from stock setting of 112.5?  I thought that the main jets installed had to be "richer" to compensate for the addition of an aftermarket exhaust?   Am I wrong?  Once I reinstall my original exhaust and put in 112.5 Mikuni main jets, will it not run rich at the top end?
Please guide me in the right direction!

Thanks again,
Dean

[RichBaker]

I'd say the DJ112s are on the lean side anyways. I'm running a D&D exh., UNI pods and have DJ114s in my '90. Mik 40 pilots, DJ144 air corrector and 2nd groove on the DJ needle.  The stock mains are pretty close, on the '80s and '90s Jap big bore bikes, most, if not all of the emissions tests are run at very small throttle opening, so the pilots tend to be set lean, the EPA test cycle never gets into WOT, so the mains are good, with stock exh. It may need 1 size up with an aftermarket exh.

[racerrad8]

Dean,

If you are putting your carbs back to stock, here is everything you need in kit form which will be much cheaper than buying everything individually. No need to try and figure out the conversion from DJ jets to Mikuni...

The kit has the stock needles & jetting for your bike as well as replacement N&S, e-tubes, idle mixture screws plus several more parts.

Carburetor Rebuild Kit 88-95 FJ1200

The only thing you do not get is a full compliment of o-rings for the carbs, new intake manifold o-rings or the replacement S/S allen screws, but you can get that kit as well.

FJ11-12/XJ12/XJR13 Carburetor Kit

1.  Is there a difference between a DJ112 jet and a 112.5 Mikuni (stock for '93)?
   A) Yes, see Rich's post on conversion.

2.  Can I leave the DJ needle in?  Is there a difference?  Should I keep it at position 2?
   A) If you are wanting to change back to stock jetting, why would you leave the DJ needles in?

3.  Should the emulsion tubes be changed--would it have been a DJ part in the kit?
   A) Yes, they are 20 years old and will be worn. This causes jetting & fuel consumption issues.

4.  Having the mixture screw out at 3 turns appears to be close to original setting.  Should that be adjusted?
    A) Yes, it will need to be set correctly after you have the carbs all back to stock and sync'ed. You will be pretty close.

Randy - RPM

[Tor-King]

Thanks for your response, Randy!

That is probably the route I will be going.  Couple of quick questions about the kit you offer:

1.  I notice that the main jet is a 110 and my year of FJ is asking for 112.5.  Is there truly much of a difference?
2. Pilot jet you offer is 42.5 and my bike asks for 37.5.  Any concerns?
3.  I do not know if the slides have been drilled for accommodating the the DJ kit.  I am hearing that some older kits asked for the slides to be drilled...There are a couple of holes in the bottom if my memory serves me correct. Will this cause a problem going back to stock if they have been drilled?

I will be ordering a number of things from you over the next month or so but need to be really familiar with things and KNOW what I truly need.

Thanks again,
Dean 

[racerrad8]

1.  I notice that the main jet is a 110 and my year of FJ is asking for 112.5.  Is there truly much of a difference?
2. Pilot jet you offer is 42.5 and my bike asks for 37.5.  Any concerns?
3.  I do not know if the slides have been drilled for accommodating the the DJ kit.  I am hearing that some older kits asked for the slides to be drilled...There are a couple of holes in the bottom if my memory serves me correct. Will this cause a problem going back to stock if they have been drilled?

1&2) The jetting offered in the kits was the jetting that was offered outside of North America at the time of manufacture. North America has/had more stringent emission requirements and the jetting then was altered to pass those regulations. The jetting offered will allow the bike to run better as it is not restricted on fuel.

3) Yes, if the slides have been drilled then they will need to be repaired. I have epoxied many over the years and drilled the epoxy to the factory hole size. I use number drills for this task, not fraction sizes. I have it written down at the shop in my book, I will look it up if you need it.

You can tell if it was drilled as the gold anodizing and chamfer at the hole will be gone.

Randy - RPM

[Harvy]

3) Yes, if the slides have been drilled then they will need to be repaired. I have epoxied many over the years and drilled the epoxy to the factory hole size. I use number drills for this task, not fraction sizes. I have it written down at the shop in my book, I will look it up if you need it.

You can tell if it was drilled as the gold anodizing and chamfer at the hole will be gone.

Randy - RPM

Interesting point there Randy.

When I first fitted DJ kit years ago, I drilled my slides as instructed in the DJ kit....... but for the kit in Aus which was for a Euro spec FJ1200 (which I am lead to believe is the spec for Japanese domestic models), the amount of metal removed was minute.
Since then, I have changed jets to FP, along with emulsion tubes and needles........ there has been no ill effects from the drilled slides that I can discern......


Just my observation.
Harvy

[Tor-King]

Hi again, Randy.

Things look promising!  I just checked out the slides and it appears that the chamfer and gold anodizing is still there so I am suspecting that they have not been drilled! 

More questions:

1.  There is also a very small hole next to the needle.  Is this factory and what is its purpose??
2.  When the DJ kit was installed is it possible that the large slide spring was also changed?  I understand that it is different from OE.  Is that correct?  Can it be reused when I go back stock?

Thanks,
Dean

[racerrad8]

1.  There is also a very small hole next to the needle.  Is this factory and what is its purpose??
2.  When the DJ kit was installed is it possible that the large slide spring was also changed?  I understand that it is different from OE.  Is that correct?  Can it be reused when I go back stock?

1) The small hole is a factory hole. It is there to index the needle positioning ring, the white plastic needle holder at the clip. There is supposed to be a small tab on that plastic piece to index all of the needlesw in the same position of the e-tube.

If that tab is missing, then there is no way to keep the needles properly indexed and the mixture will vary from carb to carb. The tab is very important...

2) Several aftermarket kits did use a different slide spring. If the hole was not drilled hopefully the stock spring is still in use. Can you take a photo?

Randy - RPM

[RichBaker]

 I  installed a DJ kit in my '90 around '96, or so. The kit came with different springs (same length, but a lot fewer coils, and I think the wire was a smaller diameter.) They let the slides lift a LOT quicker....  Also, there was no instruction to drill the slides, the new springs probably eliminated that need.
The new springs have the coils spaced ~ an inch apart, the stockers were spaced ~1/4" apart.

[Tor-King]

Hi Rich and Randy,

I had a look at the springs and I am thinking they are DJ.  What I discovered:
-they are a touch less than 4 1/2" long
-total # of coils are 14
-spacing between each coil, about 3/8"

Sorry, but I cannot provide a picture but I had a look at Andy's illustrated guide and it sure looks like a DJ spring.

Randy, would you happen to have any OEM slide springs or would it be ok to stay with the springs and replace everything else, (jets and needles, that is).

Thanks again,
Dean

[SlowOldGuy]

I've swapped back and forth between DJ and OEM slide springs before and didn't notice any difference.

I also have drilled slides.  I've swapped an extra set of undrilled slides in also and again no detectable difference.

As long as you're fairly close on everything, the FJ is very tolerant of carb settings.  Get the jetting, particularly the needle position, right and you'll be okay.

DavidR.

[racerrad8]

Hi Rich and Randy,

I had a look at the springs and I am thinking they are DJ.  What I discovered:
-they are a touch less than 4 1/2" long
-total # of coils are 14
-spacing between each coil, about 3/8"

Sorry, but I cannot provide a picture but I had a look at Andy's illustrated guide and it sure looks like a DJ spring.

Randy, would you happen to have any OEM slide springs or would it be ok to stay with the springs and replace everything else, (jets and needles, that is).

Thanks again,
Dean

Dean,

Definitely sounds like a DJ spring

Here is the stock spring in the background.


I am not at the shop to be able to count the coils of the stock spring.

The DJ spring has a different rate which is designed to function with their needle profile. It will give you jetting issues when trying to tune the carbs properly as the slide speed & height will be different than that speed or height it would be with the stock spring.

The irony of your question is timely. I ordered two sets of those last week. I received three today...the other 5 are back-ordered until  Mid December.

I am sure I have a good used one I can rob out a set of my carbs I can supply in exchange for the replacement to make a full set of four.

I do not recall the price off the top of my head but they were under $20.00.

Randy - RPM