Xj550j Jetting

Alrighty, so I recently read and used the diagram chacal posted for a general jetting diagram, and got some interesting results

+4 for pod filters, +2 for stock exhaust with higher flow mufflers (stock Harley sportsters)
Then -2
=4
Then for altitude you take 2 off for every 2000 feet.. and I’m in Denver at around 5500 feet.
So.. I should downsize 1? Or stay stock? It seems to run great aside from 2000-4000 rpm gets boggy.

I’m aware I should look into color tuning but for now I guess I’d just like some advice that doesn’t involve loads of money..

 

Probably not. The formula is just a guide and a starting point, but in almost no case does the addition of pod filters require a decrease in jetting (even at 5500 feet elevation). Try this: after the engine is warmed up, try applying just the smallest amount of choke and see if that remedies the "bogginess" in your problem rpm range, or does it make it worse. This is the easy way to determine whether you're too rich or too lean.

Also, even if it DOES solve the issue in that rpm range, you may find that such a change (a little richer) may cause issues at other rpm ranges. This is one of the difficulties of pod filter addition; all of the stock jetting (along with the rest of the carb components, meaning emulsion tubes, jet needles, vac piston size/type, vac piston spring, etc.) are all designed to perform "good" across all rpm ranges using the stock airbox and paper filter; and although you can increase performance by increasing airflow (pods) in one area of engine rpm's, it may (will) decrease it at others. So it's a matter of what you want to sacrifice/gain.....typically, in street driven bikes, it's much more important to have good responsiveness and torque at the lower rpm ranges (below 5500 rpm's or so) than it is to bump up performance at higher rpms (the way to do that is to get a bigger engine.........).

 

I agree!
The bike does run much better with the choke opened just a hair.
Thank you! I’m not expecting this setup to run perfect by any means, and yea I would rather have more response at lower rpm ranges.. which is why I was wondering!
I’m content with how it runs now, but will leaving the choke barely open while riding cause me any issues?
I usually close it all the way if I know I’m doing any 6k rpm + pulls.

 

If you do that there is a risk you'll forget, and then you're on the way to burning a piston. Bigger jets and maybe raising the needle will help.

 

You won’t burn a piston by leaving the enricher on a touch. Leaving it on a touch means you’re ADDING fuel. A richer mixture burn COOLER. than a lean mixture. A mixture that is LEAN burns HOTTER, and can lead to holed pistons and meltdowns.

dfox

 

Indeed, but if you forget to put the enrichner on.....

 

Ok, went back and re-read .... now I understand your answer —— yes you’re right. If he’s running better with it slightly on, AND HE FORGETS TO PUT IT SLIGHTLY ON, then yeah, he’s probably running a bit too lean at that point an yes, can be on the way to burning valves and holing pistons.

 

I mean I found a kit that’s got a 35 pilot and 115 main.. that sounds like it would probably do the job as opposed to leaving the choke on…

 

Says it’s a “stage 1”