low rpm issue

[jjz28]

OK, my bike seems to run great but I know that something is not right below 3500 rpm. Once I get to 3500 it runs awesome, I guess that is when the mains kick in. My question is could out of synch do this? I cleaned my carbs several times but this has always been there. I don't notice it unless I am in a higher gear going through town or making a turn at an intersection where the rpms are low. If I am accelerating its not noticeable really, just if I stay in that lower rpm, I can tell. Its not a miss or anything like that, its just "off". What about gas with ethanol in it? I don't know what kind of gas I get except ive been running 93 octane. This isn't a big problem, its just kinda bugging me knowing something is not just right. The bike runs great but I know something isn't exactly right. I hope this makes sense, thanks guys. Oh, also when I start it with the choke it goes to about 2000 rpm when warmed up, it never idles up really high. Could the enrichment passage have something to do with my low rpm issue? Maybe I should do yet another cleaning.

[WMarshy]

Its typical for the RPM to be climb high when its warming up with the enricher pulled. Give it enough time and it can even get higher than 2K especially if you blip the throttle with it on and it warmed up. In the cold seasons I use that as a gauge to know when its warm enough; RPM is about 2K and it doesn't act anemic when I blip it with it on.

Most everyone (including meself) is going to tell you that the slow speed circuits are still dirty and need more cleaning. Did you remove the emulsion tubes when you cleaned your carbs last? Its likely a little lean at low rpm. Next time it's acting like this while your taking a slow turn pull out the enricher and see if it clears up. If it does then it confirms a lean condition, if conditions worsens then your over rich.

[BA80]

The 78 - 79 engines typically have a burst of power at 3 - 3.5K because of the cams and the timing curve.

[DGXSER]

Most any XS11 I have riden has a burst in power at around 3k, and again about 5k.

To your first question on synching, yes. Lack of synching the carbs can cause it to be "off" at the lower RPMs. It is still off at the higher RPMs, it just gets hidden by the fact its revving so fast. Kind of like riding fast over a bumpy road, the bumps are less noticable.

So, if you have not yet done so, synch and tune those carbs before you go thinking another good cleaning will cure what ails it, only to find you still need to synch and tune.

[motoman]

OK, my bike seems to run great but I know that something is not right below 3500 rpm. Once I get to 3500 it runs awesome, I guess that is when the mains kick in. My question is could out of synch do this? I cleaned my carbs several times but this has always been there. I don't notice it unless I am in a higher gear going through town or making a turn at an intersection where the rpms are low. If I am accelerating its not noticeable really, just if I stay in that lower rpm, I can tell. Its not a miss or anything like that, its just "off". What about gas with ethanol in it? I don't know what kind of gas I get except ive been running 93 octane. This isn't a big problem, its just kinda bugging me knowing something is not just right. The bike runs great but I know something isn't exactly right. I hope this makes sense, thanks guys. Oh, also when I start it with the choke it goes to about 2000 rpm when warmed up, it never idles up really high. Could the enrichment passage have something to do with my low rpm issue? Maybe I should do yet another cleaning.

As I posted in an unrelated thread here recently, I've been 'arguing' with my Venturer having the same issue. Finially get disgusted with it, park it in corner of garage and cover it. Like you stated, out on highway at 3800rpm and above it's happy and plugs confirm that. Aboslutly no backfire on decel, low rpm or otherwise either. Thinking weak spark of the stock 30+yr. old coils at the lower rpm ranges, even though it does show a full 14.7V at battery and positive side of coils anything above 2'000rpm. Carbs internals are clean(quadruple clean at the least) and sport ALL Genuine Mikuni stock jetting(intake/exhaust all stock and pristine cond.), dialed in idle mixes and mercury stix synced. After on and off for the past five yrs. arguing with this situation, figure I need another set of eyes with visual input as I've obviouly been missin' sumptin'. Out of frustration, has just become easier keeping the 'riding grin' to climb aboard the ST and go do my thing, LD and otherwise. So, I'm with you, any missing input would always be helpful. Meanwhile, gonna go order a couple new BT23 tars from KeelBrothers for the STeed.