98 carb question

I’ve just acquired a 1998 900SS CR. Love the bike, but it doesn’t want to idle. It starts fine, idles for a few seconds at 1000rpm then slowly climbs to 3000rpm and stays. I’ve checked for vacuum leaks but couldn’t find any. I’ve also check the choke. I think it might be running lean or the carbs may not be balanced. Any of this sound familiar?

Have you tried turning the idle adjustment screw on the carb yet? Also, does it do this while the choke is on or just until the bike has warmed up and the choke is turned back down. Sorry, I'm not an expert but I did fiddle with the stock carbs a bit before I replaced them with the FCR's.

Regards,

Jeff

The stock Mikunis can be dialed in pretty good, but ultimately they are finicky. if you look, there are MANY vacuum and vent lines open, more or less, to the atmosphere, and thus subject to many variables in temp, humidity, etc. Plus, the needles and tubes wear out quick, which renders all subsequent adjustments meaningless.

To me it sounds like (assuming a vacuum leak has been absolutely ruled out) like a sync problem. My bike (a 97) ran waaaay better after I got the carbs synced up...and not w/ mercury sticks; not very accurate.

In the end, I took 'em off and installed FCR 41s...definitely the way to go if you like and plan to keep your SS. They make a bigger difference than you can imagine. I've put close to 1000 miles on my bike since switching, and I'm still amazed!

I haven’t touched the idle screw on the carbs. This happens with no choke and the motor warm. Funny thing is last time I checked the carbs for leaks, I put my finger over what I assume is a vent (it has a hose that connects it to a black box on the left side of the bike) on one carb and the idle slowly returned to normal. I’m going to get FCR’s as soon as I can, but in the mean time I’d like to ride it. I’m going to recheck for vacuum leaks this weekend. I’m also going to try and sync the carbs the best I can.

the black boxes on the sides are (for want of a better term) still air boxes for the above diaphragm part of the carb. maybe it's got a torn diaphragm. not that i've ever seen one do that.

Do you know if it's had the dyna jet stage I or II kit put in? If not, I'd start there rather than go through this a couple times. Sync can make a big difference. Lowering the idle speed setting to a point where it stalls until well warmed up can also help. If the hanging idle gets worse when it warms up I'd say you've got a rich idle problem but either rich or lean can cause what you are describing. The "get the FCRs" advice you are receiving is certainly bourne out by the legions of us running that setup who've been blown away with the results.

I don’t know if it’s jetted or not. It doesn’t seem to get worse when it’s warm. If I gap the throttle it’ll go down to 1000 then slowly rise back to 3k.

Are there supposed to be one way valves on the hoses going to the “little black box�?

Sent you an IM

As mentioned above if the jets are warn oval they are useless and you'll be wasting any time spent trying to set the carbs up. I had a similar poor running problem on my little 600SS - I did the full monty, set up the float heights properly (check out that ducati suite site), replaced the jets, fitted a S2 kit, synced them and did the valves too. Hey presto she ran like dream and still is a festy little bike for a 583cc job.