idle / low end problems

[candyman]

Looking for suggestions on what to try next.
2000 Interstate w/ just under 35k miles.

Low end was getting rough and I started getting the famous popping and cracking on decelleration. I sync'd the carbs == no help. I desmogged (and sync'd carbs again)=== didn't help. Replaced vacuum line and vacuum plugs == no good.

Now the bike is running very rough on low end and at idle. When you first roll on the throttle it acts like it wants to die then when the rpms jump up,,,,, all is well, until you let off the throttle then it crackles and pops again. I checked the plugs and from what I could tell, they all had spark.

MY uneducated guess is that I have dirty carbs and possible clogged jets ??? I'm running some cleaner through this tank of fuel but it definitely isn't clearing up yet.

Thoughts and opinions are appreciated. Solutions are very appreciated 

[Patrick]

Sounds like you have a classic case of varnished low jets.

But, I'm also a bit concerned of the list and progression of your repairs. Carb sync is done last, after all other work has been done.

[WintrSol]

I agree with Patrick - pilot jets, or the ports that deliver the pilot mixture on either side of the throttle plate may be partially blocked. Give the fuel system cleaner a chance - sometimes it takes a full treated tank and some time to wash the goo away. Taking the carbs off for cleaning is something I do last, after the cleaner fails (or, sometimes, makes things worse).

[ammpro]

May also be a vacuum leak. Too much air at idle will cause a rough idle.

[candyman]

Patrick, I synced the carbs first to see if that would fix the problem. I then synced them everytime I tried something else.
The initial sync was me being hopeful that it would be a quick fix. .................. NOPE

[Patrick]

Patrick, I synced the carbs first to see if that would fix the problem. I then synced them everytime I tried something else.
The initial sync was me being hopeful that it would be a quick fix. .................. NOPE

OK, it didn't seem from your post that a sync was the very last thing after you fixed all the vacuum leaks[ replaced lines and caps]

If the airbox is reinstalled correctly [ easy to have  a tube rolled on the inside] and there are no vacuum leaks and the sync seemed OK, then I think there is a low circuit varnish issue which is plugged lows along with related circuit passages. Some fellas have only cleaned or replaced jets without cleaning related passageways and ended up having to do the job again. I probably should have been more specific in the first response.

I agree with trying the cleaner first. Heavy doses of cleaner [ full cans per tank] and it may take several tanks. Ride this monster at as low an engine speed as it will go and still run somewhat good. Keep slowing the engine speed down as the engine runs better until it'll run and accelerate smoothly in high gear from a fast idle. Then give it another sync just for practice.

If that doesn't fix it, then its time to get your hands dirty again and pull the carburetor assembly. It can be done by pulling the intakes and float chambers, but, those screws can be troublesome and are easier to get rough with when the assembly is on a bench.

[sandy]

I agree with all the tips. There's another thing. How are the clamps on the intake runners and the O rings at the base of the polished runners. Don't think this is it but check the exhaust nuts (7-9 ft/lbs). Keep feeding the carb cleaner as suggested.

[old2soon]

Full can of B-12 Chemtool per tank for 2 full tanks at least. And keep the R P Ms below 3 grand. The hard part will be staying below 3 grand!  RIDE SAFE.

[candyman]

Patrick, THANK YOU
I'll give the cleaner a go then i'll be ready to get my hands dirty.
Sorry I wasn't more clear. I went back and reread it and I typed in circles. (long shift last night)

Anyways, I really appreciate the tips. It's kind of the way my brain was pointing me. I will increase the dose of the cleaner though !!

Maybe I can tell the wife I need an ultrasonic cleaner now !!!! heheheh

IF i go into the carbs. Do you think I should "rebuild" them or just clean them ?

[EddyH]

I had the same problem with my 2001. Try screwing the pilot screws in and snug them a little, back them out and snug them in again. Then back them out  2 1/2 turns. Worked for me. Got rid of the popping and helped smooth my idle. Cobra exhaust sounds sweet on both acceleration and deceleration again.   

[Patrick]

Patrick, THANK YOU
I'll give the cleaner a go then i'll be ready to get my hands dirty.
Sorry I wasn't more clear. I went back and reread it and I typed in circles. (long shift last night)

Anyways, I really appreciate the tips. It's kind of the way my brain was pointing me. I will increase the dose of the cleaner though !!

Maybe I can tell the wife I need an ultrasonic cleaner now !!!! heheheh

IF i go into the carbs. Do you think I should "rebuild" them or just clean them ?

Many, if not most, replace the low jets, and, many change to 38s. I just clean them along with the passages. I grew up playing with and drilling jets, so, its not hard to clean them.

Eddy makes a good point. Resetting the pilots [ and opening them a bit more] will tend to disturb the varnish and can make the cleaners job easier.

[da prez]

  O=K , here is a test that will cause a lot of  #$@^&%*. With the bike idling , a can of carb cleaner spray with a spray straw or starting fluid with a spray straw. Just give a small spray around the base of one runner and then go up one connection etc. If the rpm increases, you have a vacuum leak Do not over do the spray. A two second whiff will let you know if you have leakage. Check all lines and connections and repair as needed. As for the carbs , If you go thru the job of pulling them , rebuild them . You have them out and if they need cleaning , you are only a little ways away from rebuilding.  Take your time , do it right , not twice.

                               da prez

[Ricky-D]

There is nothing to do regarding rebuilding the carburetors. Cleaning is about it. And removing the carburetors from the engine is absolutely the last thing that should be done.

The incidence of problems arising from removing the carburetors is high and the expected difference of results (improvement) of doing so is very low.

Everything that would need to be done to the carburetors (cleaning) can  be accomplished with the carburetors staying on the engine.

***

[Pete]

Sorry to disagree.

Properly cleaning the carbs is the best thing you can do for a bike with carb issues caused by setting.
I always pull them off as it is easier to get a superior cleaning.

Yes the potential for screw ups is greater with removal. But there  is a greater potential for finding all the issues. And potential does not have to translate into actual.

Knowing what you are doing is certainly a plus, as is careful and thoughtfull execution of the process.

It is not rocket science so any average intelligent individual can do it.

I have done several without any problems and I am not a professional mechanic.
And it always fixed the problem and I did find other issues (other than dirty carbs), like bad orings, clogged filters, bad vacuum lines, mal adjusted carbs, rusted fuel tanks and bad petcocks. 

[The emperor has no clothes]

Sorry to disagree.

Properly cleaning the carbs is the best thing you can do for a bike with carb issues caused by setting.
I always pull them off as it is easier to get a superior cleaning.

Yes the potential for screw ups is greater with removal. But there  is a greater potential for finding all the issues. And potential does not have to translate into actual.

Knowing what you are doing is certainly a plus, as is careful and thoughtfull execution of the process.

It is not rocket science so any average intelligent individual can do it.

I have done several without any problems and I am not a professional mechanic.
And it always fixed the problem and I did find other issues (other than dirty carbs), like bad orings, clogged filters, bad vacuum lines, mal adjusted carbs, rusted fuel tanks and bad petcocks. 

+1 . I tried getting mine cleared up with techron, sea foam with no success. Pulled and cleaned with excellent results. The hardest part is getting the air dam and air box back in correctly. 

[Pete]

I do not take the air dam out I just remove the rear engine hanger and move them aside.