after warming up my 96 900SS SP (carbed) to operating temp, and taking it for a spin on an average temp day (90's usually) in stop and go traffic, the engine seems to want to start climbing in revs when i shift in neutral when coming up on a red light (oil temps will be anywhere from 110C to 130C). it will keep climbing as far as 3k RPMs (maybe a tad more sometimes), as if the choke was engaged. it doesn't do this until warm, though. the idle when cold on it is actually a bit lower than it should probably be (it dies pretty easily if i don't use the choke, even on a very hot day); about 1000 RPMs. i am able to "force" the RPMs down, only by shifting in 1st and letting off the clutch a bit to let it partially engage...and the RPMs will sink to the proper idling range, around 1200 or so RPMs. this problem happens consistently, even reliably.
any ideas? i would pull the carbs out but it's my only transport, and i have zero experience with carbs, so i wanted to wait for some opinions first.
Sounds like you need to synch your carbs.
Try opening your idle mixture screws by about 1/4 turn. It sounds like it's way too lean.
Quote from: Hedgehog on July 17, 2008, 09:45:36 AM
Try opening your idle mixture screws by about 1/4 turn. It sounds like it's way too lean.
i take it you mean counter-clockwise?
Quote from: McKraut on July 17, 2008, 09:48:29 AM
i take it you mean counter-clockwise?
Yes, counterclockwise. Opening means allowing more fuel to flow.
This has happened to me on the 93 900SS. I take it they are the stock 38mm Mikuni's?
The low speed air screw is a good idea, but no more than a 1/4 turn if it runs good.
What worked for me, was to back off the idle screw a touch until idle was just over 1000 and smooth.
Do NOT touch the screw behind it, that is the sync screw and will give you much more problems ;)
This problem would get worse in the summer as it got hotter.
The Ignition advance kick in early, at 1500 Rpm's
i will try out the idle screw adjustment this weekend. i will say though, that once it's warmed up, it seems to idle where it should, about 1400 or so. as for the carbs, they are stock mikuni, but thought i remembered reading that they were either 39 or 41mm, but i could be imagining that. i'm not 100% positive what the needles are, though.. the previous owner didn't know if dynojet needles had been installed or not. i haven't wanted to mess with taking them out though just to look, since i'm not familiar with carb removal/installs. also of note, i've noticed some pronounced popping on hard deceleration...has me wondering what all needs adjustment carb-wise.
Quote from: McKraut on July 18, 2008, 06:25:00 AM
i will say though, that once it's warmed up, it seems to idle where it should, about 1400 or so.
This is confusing. I thought you said that you have a problem with the idle jumping up to 3000 RPM. Just to clarify: the stock carbs don't use a choke. They use a bypass system that adds both air and gas. It's like adding another carbureter alongside that runs rich. Your bike will idle very quickly with the choke open. You should only be using the choke for starting out. On mine, I shut the choke completely off after riding about 2 blocks. Idle should be about 1200RPM after fully warmed up. They don't seem to warm up very quickly just sitting there. Cold, mine balances on the edge between stalling and running 3000 RPM for a long time. It takes fine movements of the choke lever to take care of that, unless I just get on it and ride it a couple blocks.
Quote from: Hedgehog on July 18, 2008, 09:53:25 AM
This is confusing. I thought you said that you have a problem with the idle jumping up to 3000 RPM. Just to clarify: the stock carbs don't use a choke. They use a bypass system that adds both air and gas. It's like adding another carbureter alongside that runs rich. Your bike will idle very quickly with the choke open. You should only be using the choke for starting out. On mine, I shut the choke completely off after riding about 2 blocks. Idle should be about 1200RPM after fully warmed up. They don't seem to warm up very quickly just sitting there. Cold, mine balances on the edge between stalling and running 3000 RPM for a long time. It takes fine movements of the choke lever to take care of that, unless I just get on it and ride it a couple blocks.
oh...okay, well, choke, high-idle lever...whatever it is really...i use that to try to warm it up for a couple minutes (but need to use it even if it's 95 degrees out, or it will stall). idle while cold is just barley over 1k RPMs. once it's warmed up significantly the idle is around 1200 or 1300, and there's no risk of stalling.
the main problem is that once the bike is fully warmed up (like 220 or 230F oil temp), when i shift to N, the idle RPMs just start climbing, and will top 3k RPMs, if i don't "force" them back down, by partially engaging the clutch, basically bogging it down. then it idles as it should, and will stay at that idle and will not climb, until the next stoplight, when i shift in N..... rinse and repeat.
Quote from: McKraut on July 18, 2008, 01:42:43 PM
oh...okay, well, choke, high-idle lever...whatever it is really...i use that to try to warm it up for a couple minutes (but need to use it even if it's 95 degrees out, or it will stall). idle while cold is just barley over 1k RPMs. once it's warmed up significantly the idle is around 1200 or 1300, and there's no risk of stalling.
the main problem is that once the bike is fully warmed up (like 220 or 230F oil temp), when i shift to N, the idle RPMs just start climbing, and will top 3k RPMs, if i don't "force" them back down, by partially engaging the clutch, basically bogging it down. then it idles as it should, and will stay at that idle and will not climb, until the next stoplight, when i shift in N..... rinse and repeat.
If you watch your tach you will probably notice the tach climbing slightly over 1300 just before this happens. Also, keep in mind the tach on the bike is not as accurate as you would like, particularly at idle. As said before, turn the idle down a little. Out of synch carbs will cause this problem also.
Quote from: howie on July 18, 2008, 02:42:53 PM
If you watch your tach you will probably notice the tach climbing slightly over 1300 just before this happens. Also, keep in mind the tach on the bike is not as accurate as you would like, particularly at idle. As said before, turn the idle down a little. Out of synch carbs will cause this problem also.
agreed, if it can't stay between the 1000 and 1200 the carbs need sync'd
dmf
there are easy homemade ones posted on the DMF
to be honest i don't think i can adjust the idle down any lower than it is...as it is it dies pretty easily if i don't warm up for a couple minutes, even in warm weather, and once it's warmed up, at stoplights, it's not like it's a couple 100 RPMs over normal, it's a couple K(1000) over normal... i.e. 3xxx RPMs instead of 1200 RPMs. so it's not like it's just a little bit off... i've never sync'd carbs; i'm guessing this is a tech level above me...i may have to take it in for this...
Quote from: McKraut on July 20, 2008, 10:17:47 PM
to be honest i don't think i can adjust the idle down any lower than it is...as it is it dies pretty easily if i don't warm up for a couple minutes, even in warm weather, and once it's warmed up, at stoplights, it's not like it's a couple 100 RPMs over normal, it's a couple K(1000) over normal... i.e. 3xxx RPMs instead of 1200 RPMs. so it's not like it's just a little bit off... i've never sync'd carbs; i'm guessing this is a tech level above me...i may have to take it in for this...
I think we covered this pretty well, already. Carby ducks are very cold blooded. Mine won't idle properly without some "choke" unless I take it for a short ride. When cold, the idle speed runs away pretty quickly on the "choke", and the difference between 3000RPM and 1200RPM is less than a tenth of an inch of "choke" lever movement. You have to set the idle when it's hot. No offense, but just get over the idea of standing by your Duck like Joe Cool, putting on your gloves and helmet while it's warming up. Put your stuff on, choke the thing, start it, and go. Flip the choke off after a couple of blocks, and you're done. Or adjust the "choke" lever every few seconds while you're getting dressed, of course.
Quote from: Hedgehog on July 20, 2008, 11:25:45 PM
I think we covered this pretty well, already. Carby ducks are very cold blooded. Mine won't idle properly without some "choke" unless I take it for a short ride. When cold, the idle speed runs away pretty quickly on the "choke", and the difference between 3000RPM and 1200RPM is less than a tenth of an inch of "choke" lever movement. You have to set the idle when it's hot.
i guess it would make sense to set the idle for a "hot" engine...sort of. but to be clear...i should go out riding, come back, and then mess with idle while the engine is still at full operating temp? this will pretty much make it absolutely impossible to ever start it even in 105 degree weather without full choke. something doesn't sound normal about that...but i just want whatever's best for the bike.
Quote from: Hedgehog on July 20, 2008, 11:25:45 PM
No offense, but just get over the idea of standing by your Duck like Joe Cool, putting on your gloves and helmet while it's warming up. Put your stuff on, choke the thing, start it, and go. Flip the choke off after a couple of blocks, and you're done. Or adjust the "choke" lever every few seconds while you're getting dressed, of course.
Quote
none taken man...because i sit on my bike when it warms up...i've never liked the idea of just starting it and walking away. it makes me paranoid.
Quotei should go out riding, come back, and then mess with idle while the engine is still at full operating temp?
Yes. You either want it to idle right when it's cold (it won't stay cold) or you want it to idle right when it's hot (it will get hot).
Quotethis will pretty much make it absolutely impossible to ever start it even in 105 degree weather without full choke.
Why does it matter whether you have to use the choke or not when it's hot? Remember, it's not actually a choke; it's another carburetor. But, actually, I think you'll be surprised. When cold, choke it and thumb the starter, but don't mess with the throttle. It'll start right up, idle at 1200 for a few seconds, then head for 3000. From there, lower the choke till it's idling about right, then take off. The idle will clean up usually within 3 blocks, and you can turn the choke lever completely off. I just click it off while riding. When it's still hot from a ride (say an hour maybe) then just hit the starter; again, don't use the throttle. When it's setup right, it's generally harder to start if you insist on trying to use the throttle while cranking. There's no accelerator pump, so there's no real point in it, anyway.
Also the reason the idle seems to jump so high over the 1200, as you stated 3XXX, is because of the ignition system.
The ignition modules are set up to advance to full advance (around 32 deg BTDC) at a low 1500 rpm's.
This causes the engine to accelerate when under no load to the 2800 - 3000 range. Under load it can be controlled better, but doesn't like it that low.
Quote from: Hedgehog on July 24, 2008, 06:25:56 PM
Yes. You either want it to idle right when it's cold (it won't stay cold) or you want it to idle right when it's hot (it will get hot).
Why does it matter whether you have to use the choke or not when it's hot? Remember, it's not actually a choke; it's another carburetor. But, actually, I think you'll be surprised. When cold, choke it and thumb the starter, but don't mess with the throttle. It'll start right up, idle at 1200 for a few seconds, then head for 3000. From there, lower the choke till it's idling about right, then take off. The idle will clean up usually within 3 blocks, and you can turn the choke lever completely off. I just click it off while riding. When it's still hot from a ride (say an hour maybe) then just hit the starter; again, don't use the throttle. When it's setup right, it's generally harder to start if you insist on trying to use the throttle while cranking. There's no accelerator pump, so there's no real point in it, anyway.
sounds good man...i just wanted to feel comfortable that i was treating the bike properly. it always starts right up with high idle; never a problem there. so i'll just continue to do that and screw with (literally) the idle to set it for a bit lower than it is now. thanks again.
after going for a couple more rides and thinking about this further, i'm not sure i agree with this solution of adjusting the idle down further. my reasoning is that the idle seems to be fine (albeit on the low side), it's just that there is an unintentional "high idle" when the motor hits higher temps (130C+). i can still force it back to the normal 1200ish RPM idle; i just have to put it in gear, and let the clutch out a bit to bog the motor down...and then it just "finds" the correct idle again. so adjusting the idle would not really be a "solution" to the problem, in my mind. there is something else at work here that needs to be addressed, i'm just not sure what it is.
Did you richen up the idle mixture yet? If not ...
you need to sync your carbs.
http://www.ducatisuite.com/carbsynch.html
this link gives you the general idea.
you don't need fancy gauges though, just get some clear vinyl tubing that fits the emissions nipples (i think it's 5/8" ???). you'll need about 12'. take the middle of the tube and secure it to the bottom of a yard stick, secure (with tape or wire) the tube up both sides of the stick and fill the tube with water so that it comes up the stick about half way. i then drape your new "differential manometer" over the handlebars and connect the ends to the emissions nipples. kink the tubes with a vice grips/clamp, and start the bike. let it warm up then remove the clamps. if the water doesn't stay level then you need to adjust the synch screw (hiding above the idle speed screw) until they are reasonably level.
to adjust the sync screw you normally need to loosen the oil cooler to get it out of the way. it's kinda hard to reach otherwise.
it's really not that hard, and once you have done it the first time it's really easy to do it again.... kinda like makin' [bacon].
edit: oh, and the reason this happens is that your carbs are essentially fighting against each other. one cylinder/carb is trying to operate at one speed/opening and the other at a different speed/opening. when it's cold the slower carb is winning. once it gets warm, the faster carb is winning.
Quote from: sur4die on July 29, 2008, 01:23:00 PM
you need to sync your carbs.
thanks for the info man...i appreciate it [thumbsup] SUPER DUKE! (aka RichD of the "PugglePod" fame) here in the DFW area with an SS (and a 1098) agrees with you about the syncing. i'd like to give it a go myself; hopefully in the coming week or two i can give this a try.
thanks again!