[tooseevee]

     On my '08 AVL Classic I spent a lot of time dialing in the Mikuni BS-29 to the K&N & the Sportster muffler. Then I came across the for free, wide open, old Brit bike bottle pictured & have been doing it all over again & although I've found "OK" combinations, it hasn't been "sweet" yet. This muffler DOES sound more like an Enfield should.

       So today I raised the needle one more shim & replaced the 15 Pilot with a 17.5 & the mixture screw 1 1/2 turns out just to see what would happen.  Horrible. Would not kickstart for shit (usually 1 or 2 kicks & it was running, cold or hot), idled & ran like shit on the road once I did get it started.

        So I removed the one shim I had added plus one more & pulled the 17.5 out & replaced it with a NEW from CMW 15 Pilot jet. This time it ran gorgeous, kickstarting back to normal, idle good, 1 1/4 turns out on the mixture, all good, really nice BUT!

         The engine was very slow to return to idle when the throttle was rolled off. TOTAL pain in the butt, totally screwed up shifting . It would return finally if allowed to, but very slowly.

          So I put the ORIGINAL 15 Pilot back in - the one that was in it before, the one it came with - and that made the problem go away. It returned to idle quickly just as it should.

           Any ideas how that would happen? And yes, I know they are both 15s - I use a maggerfrying glass - exactly same.

            The next day I feel like torturing myself (it was WAY too hot to do this today) I have to figure out why I can turn the mixture screw all the way in & the engine will still run. I don't get much of a change in RPM as I screw it in slowly all the way so I just leave it at 1 1/4 turns out. Seems OK. I can idle it dangerously slow if I want to, but I keep it right where the shifter doesn't clunk into 1st - just a little "click". (Yes, I do wish it had a tach).       

[tooseevee]

   
       So I removed the one shim I had added plus one more & pulled the 17.5 out & replaced it with a NEW from CMW 15 Pilot jet. This time it ran gorgeous, kickstarting back to normal, idle good, 1 1/4 turns out on the mixture, all good, really nice BUT!

         The engine was very slow to return to idle when the throttle was rolled off.

          So I put the ORIGINAL 15 Pilot back in - the one that was in it before, the one it came with - and that made the problem go away. It returned to idle quickly just as it should.

           Any ideas how that would happen?

            So nobody had any ideas for me about what would cause this & now after having ridden around a couple of times since 6/23 with it being perfectly OK, it's back. It won't idle down quick enough to be able to shift right up OR down. Hurky jerky ridiculous unpleasant aggravating.

              Nothing is sticking. The cable returns the carb to idle postion instantly. All the times I've had the slide out, it runs totally freely.

               Could I maybe still be one shim too high (rich) on the needle? That's what I'm gonna try next.

                Guess I'll go Google the question. It's too blasted hot & muggy here to ride anyway + "they" are all out in force trying to get to the beaches before the water's all gone & "they're" all lunatics, young AND old.

[GreenMachine]

That a good one..I'm assuming you tried running the seafoam thing? When u release the throttle do u hear the slide snap down in place.. I know on the Micarb, the throttle cable works with the carb spring which in turns lifts the slide  as well as the needle. Do you have the proper amount of play at the throttle. ...Not a huge difference between those pilots..It has to be a cable thing, weak spring, air mixture screw stripped ..You might be taking that carb off the bike  and giving it a good look over again..

[Arizoni]

IMO, there can only be one reason the engine is not returning to an idle speed.  The engine is getting too much air when the throttle is closed.

If it is not the throttle slide failing to fully return to the closed position it must be a air bypass circuit is too far open or there is a air leak between the carburetor and the engines inlet valve.

If there are rubber parts between the carburetor and the cylinder head they should be examined closely for any small crack or area which is not fully sealing against the mating metal parts.

I don't know if your carburetor has a flange but I assume it does.
More than once I've seen flanges which were bent or distorted which appeared to be flat when eyeballing them only to find a .020-.030 (0.5- 0.8mm) bow at the outer extremities which left the central area with a almost invisible gap in the middle area.

If you remove the carburetor it is a good idea to use a good metal straight edge to see if this is the problem.
If it is it can be fixed with a wide fine tooth file or a piece of black wet/dry sandpaper on a table top or piece of glass.

[1 Thump]

You have probably had the carburetor apart a lot trying to tune it. The rubber manifold can get cracked leading to a lean condition.

[tooseevee]

        Well, you guys have my permission to form a circle around me, point fingers & laugh your fri**in' asses off at me.
         After lunch I was sitting here listening to the latest lies on TV & suddenly like a bolt of lightning "Intake Leak"! shot through my heat-curdled brain. I'd like to say I read your posts, Areezonee & Green, before I thought of it, but I didn't. Honest.

          So I went down & gave it a shot of carb cleaner & sure enough, the idle speed rose. What happened is I've had the carb off so many times that my attention must have got diverted or something the last time & the clamp wasn't final tightened. So just to be sure I pulled it, put a very thin coat of red Hylomar on the throat & tightened her up good.

           Problem gone instantly & it's back to perfect again & a pleasure to ride. In fact I didn't even want to come home again, but it's too bloody hot for this old man.

             Green, all your suggestions are good, but none of that stuff is wrong with this carb. I'm obsessive about stuff like that (except tightening the intake flange  ). And I disagree with you on the difference in Pilot Jets, a 15 vs. a 17.5 - it made a huge difference on mine.

            Arizoni, I had checked flatness before. Plus I put a very thin coat of UltraBlack RTV on it the very first time I ever had it off.

             And the funny thing about this is that I'm used to dealing with micro-air leaks on shovelhead harleys. They are notorious because so many variables must be aligned perfectly for the whole unit to be air-tight. And there are TWO cylinders.

            Anyway. It's really running good again now, in fact excellent. I'm very close to 500 miles now so a fluids & filter change, valve set, head torquing will be soon. And install my fancy little pushrod adjusters.

             PS: Green, I've been using MMO since new; One Oz. to Two Gallons. I mix it in my garage. I hate gas stations.

               Onward & upward.
   

[tooseevee]

You have probably had the carburetor apart a lot trying to tune it. The rubber manifold can get cracked leading to a lean condition.

          Not cracked. But sure as hell loose  Read above. Or below.

[GreenMachine]

I'm glad u found it..I just assume u checked the tightness on the flange..Over the Winter, I'll probably change out the rubber between my Micarb and intake for the hell of it..The fact  that its all original since 06 makes Me want to do it as a inexpensive Preventive Maintenance item..Its a weird symptom and arizoni/thumper were on to it from the get go. No one left you in the lurch..GM