78 Xs400 2e starting issues


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So I got a non running 78 xs400 2e about 6 months ago and been slowly working and learning about it.

Got carbs rebuilt, new clutch lever cable, plugs, charged battery, new oil amd filter, cleaned tank amd put fresh gas.

The battery needs replaced. It won't charge fully. But, trying to kickstart it while jumping it off a good battery it would turn over for maybe a second and cut off then won't kick over for like 10 kicks. When it does try to start it won't stay running. When I say it starts for a second, it's a literal second.

What can I do to get it to run and stay running? Will a new battery take care of it. I figured jumping from a good battery would give me the amps needed to start but I'm not sure.

I started with the filters on, then thinking maybe it wasn't enough air I removed the filters and still didn't get a start.

It kicking over just a little bit gives me hope but idk enough to know what to try next.

Googling just said probably lack of airflow or things I've already done.

Side question. Does anyone know where to find a shift lever that fits the 78 xs400? I ordered one on ebay but it wasn't the correct angle.
If you did a good job on the carbs and you have good fuel flow from the petcock, then Fuel is okay.
It looks like your intake system is all there and hooked up, so Air is okay.
That leaves spark...

So, a few things to get you started - pull the plugs and kick the engine over with the plugs hooked up one at a time and with the plug threads grounded to the engine. You should see a solid blue sparks arcing at the end of the plug on both sides. If anything looks weak, you probably need to test the coils and look at the ignition points. Regardless, you should clean and reset the points to make sure the timing is okay.
Thank you, idk why I didnt think to do that. Replaced the plugs and just figured it was good. I'll give that a shot this week and see what's going on. I appreciate the reply.
Usually if it fires then wont run it is fueling, jetting or something . It is rare to have spark then suddenly not have spark. If you hear it fire once then its fueling. If you have a goof solid green light and red light on the IC then you have power. Here is something you can try as it always works for me .. take plugs out, put a few ml of fuel directly into each cylinder. put plug back in , if it fires then dies, its fueling . I have had my bike for over 40 years and this never fails, i have one of those plastic eye dropper things and use that to dispense fuel directly into the cylinder.

carbs are finicky .
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