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Hey Honda Twins world!
I'm new here & pretty new to the vintage honda biking community. Just browsing around the forums & posts, it seems like a pretty awesome network. Hope that I can learn a lot from you all. Thanks for taking the time to read & post.

Heres the problem: My bike is a Honda '75 CB306T. I've had it for about 3 years, and it ran pretty well. Lately it's been struggling to keep a strong idle at slows & stops. I'd have to pull in the clutch and blip the throttle to keep it alive. It would be running okay until like 10 mins of riding around the blocks, but at stops signs & intersections I'd get nervous b/c I'm afraid it'll stall out. But as long as it has gas its okay.

Heres what clears out: I recently took it to a mechanic. He checked the valves, plugs, battery oil, carbs, etc (which all seemed to check out). He did replace the throttle cable (which had a lot of play), but I have no idea if that can be related. Everything else seems basic (choke, fully charged battery, fuel tank full) & seems okay.

Now my question is: What other checks am I missing or need to examine for a case like this? Is it mechanical (the cable), electric, or fuel/carb issues?

Thanks y'all!
 

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First guess is that your battery is dying - if you keep it on a trickle charger at home, it’ll run fine for the first little while, but the charging on these bikes is weak enough that you aren’t charging until at least 3k rpm, and as your battery weakens from that deep cycling, it’ll last shorter and shorter before it starts sputtering at idle. I’d say short term fix is replacement battery; I’ve tried Lead-Acid ones, AGMs seem to be tougher.

Long term, it’s worth investing in reducing your draw and boosting your charge. It’s cheaper to reduce your draw than to boost your charging (the only way to really improve your output is a rewound stator/Rick’s upgraded stator). You can do an upgraded Regulator/Rectifier to more efficiently manage the charge you’ve already got - Sparck Moto is a good way to go for that.

Reducing your draw is the better bang for your buck I think - swapping your always-on lights to LEDs will go a long way. LED headlight alone with get you near even at idle. There are much better electrical guys on here than me, but I think it’s somewhere in the neighborhood of 30 Watts of your 120 from the stator go to the headlight (someone please correct me :) ).

Anyway - to confirm, take a multimeter with you on your next ride, pull off when it starts sputtering, and read the current across the poles (bike off). If it’s below 12.6v, the battery’s it.
 
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