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That sounds like the battery performance you’re looking for. Test it a few more times over the coming weeks to make sure those numbers stay consistent, and you’re good. Your hesitation could be completely unrelated! As for your shifting, it all depends on how much gas you’re giving it, uphill/downhill, etc… If you don’t have a tach, a good rule of thumb is about 4-5 seconds of ‘normal’ acceleration in every gear. Don’t worry too much about short-shifting. These engines are made more for torque at the low-end, so not much sense revving them out unless you really want to hurry! You’ll get to know it by ear.
 

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You could also try connecting a non-running car battery using booster cables, and see if the bike tries to start right away. That would point the finger at the battery for sure. Always worth cleaning the switches, though!

I’ll have to watch it a little as my bike has both more power AND a tachometer compared to yours. One stupid question. Are you SURE you’re in first gear? A member of a sports car group I belonged to had that same problem. ‘No power in first until it’s up to speed.’ I helped him figure out that his first gear was really third, since he’d put the wrong bracket on his shift cables! Because in first gear, twisting the throttle at anything beyond walking speed should give you all the power you need. It’s not a ton compared to other bikes, but it should be enough that you don’t consider it ‘bogging’ to 25mph. So if the bike is idling, you give it a little less than 1/4 turn of throttle and let out the clutch to get it rolling, with the clutch fully out at around 5mph you should be able to give it 3/4 to full throttle (watch out in front!) and the bike should GO. If it doesn’t, if it hesitates or bogs, then you’re in the wrong gear, or you have an air/fuel mixture problem. I would say the engine should be turning 3,000 rpm or so in first at 5 mph?
 

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Yeah, there’s a lot going on here! The other thing you could do with the car battery connected was check the voltage levels to compare with the ones you had from before. Yes, the headlight is supposed to go COMPLETELY off when the starter button is pressed, not dimmed to the point of being almost off. The only other thing I would be curious about is if you removed the spark plugs before trying the first start, just to see if it turns over easier without any compression. From what you say, the engine doesn’t even turn over at first.

Videos of what you‘re doing would help a lot, rather than keep us asking questions. If you don’t mind the ‘publicity’, the easiest thing is to make a YouTube account, upload the video there, and then post the link here.
 

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The demands for money come later… LOL! 😄

No, that was VERY helpful! Yes, Shadows in stock form are usually quite cold-blooded. They need a lot of encouragement. Some feedback from me on the first video is that the engine is turning over nicely (cranking, not starting), so no need to pull the plugs for a test, like I mentioned. In that cold, the battery seems to be doing pretty well, too (or was that jumped from the car?). After the first couple of attempts, you’re not quite holding down the starter long enough to give the engine a chance to ‘catch’. Once you start hearing the repeated ‘ba-duh-pa-ba-duh-pa‘ of it trying to fire, hold the starter down longer and try cracking the throttle just a TINY bit for around a second. Done properly, the engine should now start REALLY sounding like it wants to go. Feel the throttle out, and listen while you open and close it, to get it to finally start. An alternative is to spray a bit (don’t go overboard) of starting fluid (ether) around the air intake. This stuff ignites more easily than gas, so helps get the engine running faster. You don’t use too much because if a lot ignites at once, it can hurt your engine.

For the second video, yeah, it’s REALLY falling on it’s face when you try giving it a little throttle. I can’t remember if you’d said if you had opened the carbs up for a cleaning or not. At this stage, you could try running a bottle of Seafoam or another type of cleaner in your gas tank. With the engine running, try to hold it at the point where it’s stumbling, but still running, for a bit. Hopefully, the cleaner will be drawn through those particular passages and eventually clear away any buildup in there. I would keep the choke on for longer than a minute, though. It mostly depends on temperature.

The underlying reason is the engine isn’t getting as much fuel as it wants to run properly.
 

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I’ve been known to do computer work for cookies! 😉

Well, the switch advice was more when you said ‘nothing happened’ when you pushed the button. Like NOTHING. And if that was the case after reassembly, it wouldn’t hurt to clean it up a bit. Your current plugs should be fine for only being a year old. Could you remove them and post pics of what the bottom part of them look like? You could also try @oldguy s’s gap advice to see if it helps. A cold engine runs fine on choke (extra fuel being provided), but once warm will not run quite right because that same amount of fuel is now too much. I caught that slight stumble in the second video as well, and it’ll be exaggerated when riding because the engine is demanding more fuel than at idle. Like you say, it suddenly ‘picks up’ at 25mph, probably when fuel starts flowing through the fast jets as well. Like @gdb069 says, the Seafoam was a Hail Mary measure. Think you’d be up to removing the carburetors and looking inside the bowls to see if the jets need cleaning? Do it carefully and you can just re-use the same gaskets, so no rebuild kit required. Like he also says, when everything is running right, it should start on choke only.
 

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I’ve never used a torque wrench, but since I was young I was pretty good at estimating the amount of torque I was using with a regular wrench or ratchet. Of course, since getting older… “Yeah, that’s about 60lbs!” Measures about 30lbs with torque wrench 🤦‍♂️ In the case of spark plugs, I always just brought them in so they wouldn’t turn anymore without force, and then ‘cinched’ them to about 15-20ft-lbs. The plug itself would just barely move any extra. Even if you’re not strong, so long as the plug isn’t rattling around in the bore and seals, you should be good! Maybe re-check after a bit of running.

Maybe sweep the area with a borrowed magnetic sweeper to find that spring? The problem is they bounce when they hit the floor, and wind up somewhere in Paraguay… 😳
 

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Yes, the condition of the spark plugs can vary from side to side, never mind cylinder to cylinder. But that one looks good enough the others should be the same. Send more pics!
 

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Even if, for some reason, you split the carbs from each other, or accidentally messed up the sync screw... It's all good. With the carbs out, all you do is fully close the butterfly valve on one, and then adjust that screw until the other is the same distance 'closed' as the first one. 'Bench syncing', it's called. You can do the full sync later with gauges or manometers if you want, but that's really for optimizing. The bike will run just fine with a bench sync.
 
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