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I just purchased an old bike that had been sitting since last summer, the old gas was replaced with fresh gas, but the bike still runs a little choppy and im assuming the carbs and fuel lines could probably benefit from a good cleaning. I dont know how much it would cost to have a shop clean my carbs, but its probably not cheap. So id rather take on the job myself if it isnt too complicated.

So how tough of a job is it? I ordered the service manual and should get it in a few days. Id consider myself to have above average mechanical skill, ive done alot of work on cars in the past but never a bike or carburators for that matter. Its a 1978 Yamaha XS400 parallel twin with 2 carbs.

Also, will I need to "synch" or "balance" the carbs when I put them back on?

I have just been through the same thing. XS400 Carb rebuild. Its not tough, just make sure you keep track of parts and have LOTS of carb/break cleaner around. In terms of syncing them, if you don't disconnect the 2 carbs from each other and just clean the jets/bowl/floats you should be ok. I'm sure you can handle it!!

MrShake wrote:In terms of syncing them, if you don't disconnect the 2 carbs from each other and just clean the jets/bowl/floats you should be ok.

That's wrong. Were they synced to begin with? Were they synced last when they were dirty? etc

Taking the carbs off to clean isn't that big a deal. The simple way is to buy a rebuild kit with all new jets, orings and gaskets. Then you clean out the body, make sure the floats are set at the right height and make sure all the nooks and crannies are clean (blocked small passages make a huge difference).

Or you could try cleaning all your jets and reusing your gaskets. The first is possible, the second is possible but the second is generally a bad idea especially on a bike that old. When you clean the jets make sure that they are clean- sometimes you have to run a very thin wire through to get the blockage out.

If I let the bike sit for a few months and she's running rough, I just use spray cleaner. If it's a bike I picked up that hasn't run in 2+ years and won't start then I take the plastic/rubber pieces out and soak it for a day in a carb cleaner bath (sold in 1 gallon cans in the stores around me). That makes them very shiny too.

First time I cleaned a carb it took all day! Be patient and make sure all your adjustments are correct when you put it together. Take pictures of it as you disassemble it. I took the whole thing apart and put it back together, squeaky clean (some parts you'll want to soak a bit in a bowl) but as careful as I was, I still didnt have the screws adjusted right...took a LOT of time to adjust and readjust to get them right.