Going FROM pods to Stock airbox!

Hi, Just wanted to get some input on my jetting.


The bike is back together and have driven it a couple of km, not to far since it won't rev more then aprox 5-6k, loses all power after passing 4k rpm


Anyhow, I didn't change the jets when I cleaned and rebuilt the carbs cause I wanted to see how it ran. And now I have so I'm going to replace them in the next couple of days.

The previous owner ran cheap pods and a fairly open 4-1 exhaust. So he had fitted the carbs with these jets :
Main Jet : #120 (vs stock #112.5)
Pilot Jet : #40 (vs stock #35 XJ550)
And this is clearly WAY to rich (my plugs are black and wet after a few km)

now I'm running the 4-1 exhaust with a slightly more restricted flow due to the new muffler's small inlet and a stock airbox with a K&N airfilter.

Should I go back to the stock jet sizes or maybe one size higher?


Have a nice weekend all!
I will sit and stare on my XJ until I get hold of the new jets 8)

 

Broberg, that's a really nice looking bike............great colour!

The best thing to do would be to go back to stock sizes, and see how it performs in that environment. If you discover performance issues or detect an overly lean condition, then step things up from there, although with the K&N filter, you might find that you do have to go to a 37.5 pilot and maybe a 115 or 117.5 main fuel.

Have you checked the main jet needle to make sure it is the stock size?

 

Thanks Chacal!

Okey, Where I start probably depends on if I can get the jets from a local seller or not (everything takes time when shipping stuff around the globe )

I haven't checked the needle, are they marked or am I supposed to measure them?

 

I wouldn't go back to stock. I would assume that if you have pods and a after market less restrictive exhaust and at least try the next size up on the pilots and mains. At least that is the assumption I would make, no guarantees.
Here is a guide I found to rejet my other bike non-XJ:

By the way, awesome looking bike. Most tastefully done cafe style I have seen in awhile. Most cafe stye conversions I have seen tend to be on the cheap and a bit rat-tish looking.





Now in my case, I did not go as big on the main jet as the formula recommended. My model tended to be a little rich from the factory. Hope this helps.

 

The needles will be marked (engraved onto the upper portion of the shaft) with their "size"; for your model they should be 4GZ-3.

By the way, the correct jet specs for a Euro XJ550 models are:

Main fuel: 112.5
Pilot fuel: 37.5
Main air: 70
Pilot air: 170
Needle: 4GZ-3
Main jet: O-8
Fuel level: 2mm +/- 1mm

 

Thank you! I was going for clean looking

I just want to say that I have replaced the pods with the stock airbox, and not the other way around!


Chacal, Thank you for the specs!
I will check the needles tomorrow when I remove the carb rack from the bike.

 

man. that is a BEAUTIFUL bike.

In LOVE with it.

 

Nice bike. BTW how many goes does it take to turn aound with those Ace bars fitted?

 

VERY nice. I'd put a chainguard back on it is all (the original was black.) Exceptionally tasteful color. Good job.

 

Thank you! Yes, the chainguard is on it's way, it demanded some refurbishing first

Actually not that bad, I had to fit a 4mm extension on the steering head stop, but other than that it's the same as before

Thank you! I really appreciate your comments!

 

May i ask how you cleaned/prepped/painted the engine?

Thanks!

 

It's not that clean actually, I just took the off as much corrosion I could of the fins, The bottom half of the engine was originally black, so I just did a clean and gave it a rattlecan touch-up.

The covers where blasted with a plastic/alu mix to get the paint off (I bought a small blasting cabinet, one of hte best investments I've made!), and then sprayed with primer and matt black rattle can spray, it doesn't hold up so I'm going to respray them with 2k paint this winter. (same with the Mastercylinder and brackets for the levers, it flakes to easily)

The valve cover however is powder coated.

 

+1 on the chainguard and maybe just a tuning fork logo on the tank?

 

NICE RIDE!

 

But wait - -

I thought that the Mikuni carbs had a jetting # reference different than the Hitachis.

Meaning , you can't just get Hitachi replacement jets and toss them in a Mikuni Am I wrong on this?? It doesn't seem to be addressed in this thread

 

Since it is a 550 with mikuni carbs we have not mentioned hitachi numbers in this thread (Maybe the # in XJOE550's pictures are, but They aren't for the xj550, just as guidline for jetting another bike).

But no I don't think you could fit hitachi jets in mikuni carbs, they would probably have different outer dimensions. I have never touched a hitachi carb so I'm not 100%. But looking at the different types of jets just for the different mikunis out there I would say that all jets are probably are model or series related in shape.

 

Smart move. Pods are good but a hassle to set up. I put a set on an XJ900 and they worked fine after much trial and error but I don't think they helped produce much more power than the stock air box. Look cooler, I guess, but that's about it.

 

Okey, checked the needles and what I can read it's 4GZ16, how off is that?

 

Well, I can't find anything on a 4GZ16 needle, it may have been some country-specific needle. The closest I can find is the North American XJ550 Seca needle:

4GZ1: used on all North American XJ550 Seca carbs.

Mikuni needle "numbering" systems are somewhat complex to describe, you can use some google-foo and come up with some more detailed info, such as this:

http://www.jetsrus.com/a_jets_by_carbur ... ikuni.html

which will give you some idea of the issue involved in analyzing Mikuni main jet needle "sizes".............

In short, I think that the needles you have will be okay for your use, or, you can experiment yourself to death using other sizes..........

 

Okey, I'll leave them in there for the time beeing

Thank you all for the help and nice comments about my 550!