'81 Back Running; Now What?

NotACow

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So, first off, I'm very new to riding and am not very mechanically inclined; what I've learned to do with vehicles has, almost exclusively, come from being too cheap to pay someone else to do it.

11 years ago, my wife bought me an '81 XS400 from a friend. I rode it maybe 3-4 times, then moved and hadn't messed with it until about a month ago. I decided that I either needed to learn to ride and enjoy it, or sell the bike and free up space in my garage.

I started by cleaning the gas tank with a vinegar soak, then rinsed with water and Marvel Mystery Oil (thank you, YouTube). I've cleaned the carburetors (basically opened the things up and sprayed carb cleaner everywhere) and replaced the battery, air filters, spark plugs, and spark plug wires.

Now it's running, and it passed inspection. I've taken it out a couple times (just around town and never more than 45mph) and am wondering what my next steps need to be as I resurrect this thing. It has become progressively more reliable to start (was really stubborn the first few times, and the battery seemed weak), though the exhaust sometimes coughs and sputters. It didn't do it yesterday, but the first two days the engine would cut out when idling unless I gave it a little throttle.

I know I need to get an oil change done ASAP, and I've been told that rebuilding my carburetors will help with the idling issue (I was told it sounds like my throttle is at the right point for idling, so I might not be getting enough gas through the jets). I figured I also need to replace the tire tubes and probably the tires themselves (the back tire, I was told, barely passed inspection).

Thanks in advance for your advice and suggestions.

P.S. - I wanted to reiterate that I'm a bit of a moron when it comes to mechanical stuff, so I probably need things explained in small, simple terms (or will end up flooding this thread with even dumber questions).
 
Here's a picture of the bike, for those interested.
 

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I started by cleaning the gas tank with a vinegar soak, then rinsed with water and Marvel Mystery Oil (thank you, YouTube).
Good idea. That should keep your carbs cleaner going forward.

I've cleaned the carburetors (basically opened the things up and sprayed carb cleaner everywhere)
That isn't really cleaning.

Carburetors are finicky bastards, have many tiny passages, and just spraying might not be enough. Disassemble, spray/soak, blow out passages with compressed air, replace rubber bits as necessary.

You might be OK if it runs, tho.

replaced the battery, air filters, spark plugs, and spark plug wires..

All good ideas.

I know I need to get an oil change done ASAP, and I've been told that rebuilding my carburetors will help with the idling issue (I was told it sounds like my throttle is at the right point for idling, so I might not be getting enough gas through the jets). I figured I also need to replace the tire tubes and probably the tires themselves (the back tire, I was told, barely passed inspection).

New tires for these things aren't super expensive. And good tires are cheap insurance - it's what keeps your butt off the ground.

As far as other things:

Adjust your valves. It's a process, but does not involve additional parts. Valve adjustment is one of the most neglected maintenance items. See if this makes things better. If not... probably carbs.

Idle problems may be dirt in the carbs. You might need to clean again. Sorry, carbs are like that. No shortcuts - do it right, or do it five times.

Consider replacing the fuse box - if you search, there are many threads on this, at least a couple of them mine. Fuse boxes can fail suddenly.
 
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