1994 xj600 seca 2 rough idle

Alright so i am assuming the rough idle comes from a carb issue- at this point I either pay someone 100+ to sync things (which will probably cost more like 200 all said and done) OR ask you friendly xj folk if I have any other options.

I do beleive that the carbs were synced aabout 4000 miles ago- this bike has a yoshi 4-1 on it.

SO Symptoms:
Idles rough, seems like it might be rich because when i start the bike on a cold morning it DOESNT want the choke - I can put the choke on for maybe 10 seconds, bike starts and sputters out, turn the choke off (this is half choke by the way, full would never work) and start normally, bike fires up, idles around 500 and warms up to a rough 900-1100 range....

The bike doesnt like any RPM UNDER 2000 - trying to pull away @ 1500rpm is weak and sounds very rough, I can add some throttle to get that smooth 2k and it works fine...

Only issue with this rough lower idle is that it makes parking lots and slower travel a PITA ...

ALSO
I noticed the other day (whilst showing off during a car show I pulled out quickly- 1st gear to 8k -> 2nd gear to 8k -> Oh shit stop sign...

Running high revs up through 1st and 2nd was a bit rough, first shuddered a couple of times as if it was lacking fuel (or getting too much).

I am guessing that since the idle is rough and the carbs need some sort of adjustment that this COULD very well effect the whole RPM scale- is this true?

I was told there is an adjustment screw on the front of each carb that is easily accessed and adjusted- would playing with these (perhaps setting the all in or out and working from there...) be a good plan?

how can I spray carb cleaner on these? - is it possible without removing the tank?

 

1- it does sound as though it may be running rich.
Can we assume you have at least checked the air cleaner to be sure it isn't clogged with dirt or oil-fouled?

2- this is most likely the symptom of a bigger carb problem than just syncing/tweaking will fix, although you could try.

3- do NOT just start tweaking screws without at least some idea of what you are doing, or you will dig yourself DEEPER into the hole. Yes, the mixture screws are readily accessible, but those are LAST.

In fact, it sounds to me (just based on your symptoms) that you may have one or more floats set too high, or sticking. If that is indeed true, then no amount of screw-tweaking will fix it.

IN ORDER, no shortcuts:

-CLEAN carbs thoroughly.
-Set float levels, check using "clear tube method" with gas.
-Bench Sync.

-CHECK VALVE CLEARANCES, adjust if necessary.

-Vacuum sync (running.)
-tweak mixtures. (The screws you asked about.)

Skip any steps, take shortcuts, be less than thorough-- you will be at this a while. Sorry, no "easy answers" on carb issues; they usually have the same causes: Gummed up/varnished, clogged; mis-adjusted by PO, or by someone he paid who did it wrong.

If your valves aren't in spec, the carbs religiously clean and the float levels set correctly it will be impossible to sync correctly.

 

great start- thanks very much, I am going to check those air filters ASAP, that did not occur to me.

I read this:
http://xjbikes.com/Forums/viewtopic/t=6 ... synch.html

About bench syncing- looks pretty simple, is there anything specific to the xj600s that I should be worried about in doing this? Will this write up work for the 1-4 yoshi exhuast?

Are there any write ups on this "clear tube method"

Lastly- ( a bit off topic )
Is a clunk into first and up through N into 2nd normal? ive read about this before a few places, is it a sign of anything bad? It shifts and rides fine and steady in these gears, just with a decent (and awkward) "clunk".

 

Bigfitzs is on the money and little more needs to be added.
But You should first read;
Chacal's write up's on carbs ( and a bunch more). you can find
them on the XJ4Ever forum. They will tell you "how" the carbs
do there job and thats half the battle.
Read RickCoMatic's write ups on carb cleaning and tuning.
Then research the past forums and archives on the same
subject.
This may sound like more work then necessary but believe me,
you will spend a lot more time trying to figure out why there not working
right after spending hours cleaning them then you will reading the
correct way.
Good luck

 

Took my bike tot he local yamaha dealer today- they synced the carbs up quite nicely for about 80 bucks.

Mechanic explained to me that the previous owner cut the top of the airbox off apparently allow for too much airflow... he said the whole thing was running VERY lean ... he continued to adjust all of the piolot*? screws on each carb, he said (and i dont know what this meant...) he got them all in sync, each one reading " .1 "

regardless the bike idles VERY solid now- no ups and down and strange sputtery.

The running is still a little strange, I have to test it more (was taking it easy tonight) I am curious to see if it sputters or chokes when I take off hard in 1st or 2nd. as it did in the past.

I have not yet obtained the service manual... do these bikes have a electronic fuel pump of any sort that might be crapping out?

Also this bike (repeating this) did I beleive sit for a year or two- there is a little rust here and there in the tank, what places should I check for clogs or fuel delivery issues...

Also- should I get a new airbox?