Idle's rough down low, but runs fine up high.

pen

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Hey all, at this point I'm a regular on this site and am learning as I go. Right now, I'm experiencing an issue with my 78 model that so many have had and will have. A rough idle. Only difference is mine doesn't die on me! She sounds more like a harley than any of these bikes should while idling. Frankly it sounds like 2 and a half cylinders are firing. Though, I don't think it has much to do with the battery or the ignition as it does rev all the way to redline. I've ridden it in this state, and it does seem to have most of the power it should be making otherwise. My only idea as to what's wrong is potentially an idle jet being clogged or some vacuum leaks between the carbs and the engine.

This post might be less inquisitory and more of a blog type post following this bike's journey to smooth idling. Though tips would be appreciated as I don't know much! The next step for me right now is to check for a vacuum leak with some wd40 or carb cleaner and a trip to a supply site. After that, I think I need to clean the carbs very thoroughly, focusing mostly on the idle system. I'll also need some new bowl O rings because the old ones stretched(?) and don't perfectly fit the bowl. Right now they're held in with some red permatex. Not a great solution. I will keep this thread updated over the next couple of weeks during my free time. I know the riding season is pretty much over, but that doesn't mean I should stop!
 

pen

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A month later, and I’ve replaced the carb holders to help with a potential vacuum leak. I didn’t check for one, but the old ones were rock hard. I started her up tonight and she was fine with the choke on, still idling high at 2k so the mains would be feeding fuel. Choke off though, and was barely running. Definitely still a fuel issue, though I blame the weather (36° F). I still need to clean at least the idle jets, cause I fear they are very clogged for some reason.
 

leovich

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Double check that idle circuit is cleaned. This issue can be caused even by worn needle jet and jet needle.
 
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