[piper645]

Just picked up a 97 900ss yesterday. I guess it sat for awhile while the guy was enlisted. I was told they cleaned the carbs.

It starts and runs fine, rides fine, except that the idle is stuck at about 3800 rpm.

If I pull the plug wire on the bottom cylinder, the engine returns back down to to about 1200 with a little sputtering. If I pull the top plug wire, no change. I'm figuring that the rubber parts in the carb or going bad maybe?

I have little experience with carbs so any insight would be helpful.

 

[Joe-B]

Did you check the idle adjustment and carb synch? Also set the idle mixture screws to 3 turns out as a starting point. Sounds like it could be plugged up idle jets. Not hard to clean, but you'll have to remove the carbs to do it. Also make sure the choke is turning all the way off.


http://www.ducatisuite.com/carbadjust2.jpg

 

[piper645]

I haven't torn into the carbs yet or tryed adjusting them, but I got new plugs and installed them. I also figured out that the vertical cylinder isnt firing, but it is getting spark. The bike will also occasionally start at 1200, but when I hit the idle, it hangs at 3000-3500 rpms.

 

[bigbadbass]

minimum the pilot circuit(s) is plugged, likely the idle was set way high to
cover the problem up in order to make the sale of the bike.

A detailed carb cleaning in your future.....especially if this bike sat for over a year.

IF they were done at all, they weren't done correctly.

 

[piper645]

Well I just ordered the new rubber parts for the carbs according to what I found in another thread. So it'll be end of next week before I can make any progress on the carbs.

I need to get the bike cleaned up in the mean time. Any where that I can find the correct routing of all the wires and hoses? Everything is just ziptied in there and it looks pretty rough.

 

[piper645]

The PO had no business being near those carbs. I got them off and cleaned and found that they only took one apart, siliconed it back together, and installed the main jet wrong. I Reinstalled the carbs on the bike and that fixed my no fire on the vert cylinder, but my idle is still sitting up at 3800-4100 rpm. I set the idle screws at 3.5 turns out.
Any ideas?

Also are the starter relays known to go bad?

 

[bigbadbass]

does the idle drop if you adjust the idle screw anti-clockwise?

(still think you should have pulled and examined pilot jets and path)

 

[piper645]

I did pull apart the carbs and give them a good cleaning, don't know if I was clear on that. Maybe I should have went deeper? I replaced the float bowl gasket, jet tower gasket, main jet o-ring, float base o-ring, and the o ring on the diapghram side air passage. And the idle air screws were set at 1 1/2 turns.

By idle screw do you mean the throttle stop or air screws?

 

[bigbadbass]

lets not play a word game....the idle screw...have you simply attempted to lower the idle?

 

[piper645]

I have tried adjusting the idle mixture screws from 1 1/2 to 3 1/2. I haven't touched the throttle stop screw.

 

[AbqDave]

Check throttle cable the entire length. The ther day it slipped out of the lever fitting, stretching the wire a bit.

 

[bigbadbass]

I have tried adjusting the idle mixture screws from 1 1/2 to 3 1/2. I haven't touched the throttle stop screw.

you're complaint is high idle, yet after 2 suggestions in the thread to simply adjust the idle down using the idle screw...you haven't?

ok, attempt to turn the idle down from 3800 to 1400 or so using the idle stop screw

does it stall out or will it hold an idle?

 

[piper645]

The idle speed screw had no effect.

I can start the bike with the choke and it starts without any trouble. The idle speed is directly related to the choke i.e. at full choke idle is 3000, half choke about 1500, and no choke it will die. I'm also getting backfiring from the intake I think, especially when it dies. When I pull the plugs after it dies, they are wet.

 

[bigbadbass]

hey when you posted idling at 3800....did you mean WITH the choke ON?


if it will run on choke, but dies when choke is turned off.....

repeat....the pilot jets and path need to be cleaned

 

[piper645]

Before I pulled and cleaned the carbs it was running on one cylinder, idling at 3800. It would occasionally start and idle at 1200, but if you hit the throttle, it would stick at 3800.

After cleaning it isn't quite that high. But it will no longer run without choke. Before, it would run without the choke.

Sorry if I have been unclear, but your new questions helped me better describe the situation.

 

[Ricko]

Now raise the idle using the idle stop screw.

 

[piper645]

I guess I did only try adjusting it out to lower it. I'll give that a try tomorrow afternoon. Whats a good baseline for the idle mixture screws?

 

[Joe-B]

I guess I did only try adjusting it out to lower it. I'll give that a try tomorrow afternoon. Whats a good baseline for the idle mixture screws?

3 turns out.

 

[Sofa King]

Did you check the idle adjustment and carb synch? Also set the idle mixture screws to 3 turns out as a starting point. Sounds like it could be plugged up idle jets. Not hard to clean, but you'll have to remove the carbs to do it. Also make sure the choke is turning all the way off.


http://www.ducatisuite.com/carbadjust2.jpg

Don't forget what Joe-B said, sync the carbs. In my experience this is one of the main causes of screwed up idle, lean pops, decel pops, etc...

It's very easy to make a carb sync tool for a twin. 20' of clear 1/4" hose, hang it from a 6' 2x4 so that you have a loop hanging down near the ground and enough ATF in the hose to give you about 3' of fluid on either side. Next I used the pickup tube from inside a squirt bottle and made the two vacuum nipples because they just fit into the pickup ports on the down tubes just right with enough resistance to be airtight.

Then use the sync screw to get the two carbs in sync and get a good baseline. Then the idle setting will have more value. Otherwise the idle will constantly wander on you.

 

[piper645]

So i figured out that the idle was set way too low so it wouldn't run without the choke. I set it up to run at about 12-1300 rpm at idle. But its still not idleing right.

If I let it sit for 20 minutes, it will start up and idle fine at 1200. If I rev it up, the rpms will drop real slowly back down to 1200.

If it's running and I blip the choke, it will jump up to 3-4000 rpm and stay there, even after the choke is shut off.

While the rpm's are stuck high, i can pull the plug on the vert cylinder and the rpms will drop real low, maybe 600. If I pull the other plug, the rpms will drop maybe 3-400 rpm.

When I went to sync the carbs, my sync screw was missing. I got a replacement and did my best at syncing them. I used two vacuum gauges and got the cylinders pretty dead on. This was done at the high idle.