Stumble just off idle

[old_chopper]

Working on my '79 XS11. It has BS34 carbs (80-81 style) with stage 3 kit, pods, and free flowing exhaust. It was running slightly rough just off idle to maybe 1/4 throttle. Not terrible, just not perfect. It screams when opened up. I just put the free-er flowing mufflers on it and now I can hear the stumble / popping from #3 or #4. Carbs are absolutely clean, #3 has an issue. The carb body broke when I took the mixture jet out. I bored the body out and installed a sleeve. The location is slightly off and I can't seat the needle to back it off the 2 1/2 turns dynojet calls for. Do you think this circuit is causing my problem? I'm going to search for a body to replace it but wondered what you all thought.

[motoman]

Two issues causing your problem: 1- screwed up third carb.......2- Stage three kit, if you drilled the slides, can't go back to stock. You have a cluster you know what. IMO, find a good set of carbs and cept for a good cleanin' and proper jetting/sync. leave 'em alone. Haven't seen or heard of having the best of both worlds playing games using the Dyna-Jet kits. Snake-oil at best unless you just wanna twist it down the 1/4mile. If you were sold on the idea of "more power", ain't gonna happen, just feels like it. Ain't no different than with our old muscle cars when someone would throw a tunnel-ram and two fours on topside expecting some kind of a dragon breather. Ended up being worse than if left alone with some fine(and correct) tuning done......Bottom line, your never gonna have it happy at the low end/mid-range getting the top-end right, and vise-versa.

[BA80]

It always seems to be that #3 carb that causes problems. I haven't figured out why that is yet but I'm workin' on it.

I'm right here in Tulsa OC. I'll be more than happy to try and help you figure it out.

motoman is right though. You can't have both.

A little of both but not a lot of both...........decide where you want it.

[cywelchjr]

I would agree and disagree. Many have had good luck with a stage 1 kit, which is designed for a stock engine, while the stage 3 is designed for a modified engine. Switching to a stage 1 kit, which is basically the same as the stage 3 with different jets. It basically replaces all the worn parts that can't be replaced, with new parts that are redesigned specifically for even performance and driveability rather than plain performance like the stage 3 kits are.

[petejw]

try dropping the main jets down to dj128,
the stage 3 dj138 size jets are to big for our bikes,
even with pods and straight thru exhausts,

did u put the dj air jets in as well, if so the mixture screw settings
are 4 turns out, even tho i found that to be a bit much also,
i had mine set at 3 and half turns out.

[old_chopper]

I pulled the carbs and checked the pilot jets to ensure no blockage, they were clear. I tried 1/2 and 1 turn in on the mixture jets (started at 4 out) and made it worse, backed out to 4 1/2 out. Problem still there. Pulled the left side cover to check vacuum advance, it's working but kind of jerky. Manually advance the timing and it's way better. The carbs are 80-81 style with port on #2 where advance is hooked up. Any problem there? It doesn't appear to have mechanical advance. Vacuum line is in decent shape.

[motoman]

Pull that vacuum advance off......out of the picture so to speak and rotate the advance mechanism by hand. When touching it to rotate it should EASILY flip-flop. If it doesnt flip-flop like a bearing supported lazy-susan, its gotten a bit gummed up over the years with the factory lube. Remove it, clean and use a very thin film of LIGHT grease to re-lube. If that advance is not TOTALLY free, the Vacuum diaphram has a hard time rotaing advance soon enough off idle...........Just got through resolving the same type issue with my 81 Venturer. Make sure ALL is working properly there FIRST or you will chase your tail for a LONG time! Least that 's what was the issue with my scoot(Thanks again to 3Phase)

[old_chopper]

Pull that vacuum advance off......out of the picture so to speak and rotate the advance mechanism by hand. When touching it to rotate it should EASILY flip-flop. If it doesnt flip-flop like a bearing supported lazy-susan, its gotten a bit gummed up over the years with the factory lube. Remove it, clean and use a very thin film of LIGHT grease to re-lube. If that advance is not TOTALLY free, the Vacuum diaphram has a hard time rotaing advance soon enough off idle...........Just got through resolving the same type issue with my 81 Venturer. Make sure ALL is working properly there FIRST or you will chase your tail for a LONG time! Least that 's what was the issue with my scoot(Thanks again to 3Phase)

I will give that a go this evening. When hooked up does yours advance smoothly? Mine was pretty jerky back and forth. It made me wonder if there should be a restrictor in line to smooth out the pulses.

[MrOzz]

I agree with petejw. The stage 3 seems too much. I went down the the DJ128 also. I also found that moving the e clip to the 3rd groove down on the needle helped alot too.