Got the Bike! 1979 XS400 - Few Questions

[Bssoap74]

Hello all,

My name is John and I am from Chicago. I just picked up a 1979 xs400 with 7900 miles on it. I can get the bike to fire up and idle normal while on the side stand, but once I put the bike upright or lean the bike to the right the idle shoots up. Also the seems to be more presure comming from the left side exhaust, and the left exhaust gets much hotter. I tried adjusting the air/fuel screws 3 turns out on top of the carbs and messed with the throttle stop screw. I am not sure what the throttle stop screw does. I also get popping out of right side exhaust. Any help for this newbie would be greatly appriciated.

 

[HoughMade]

Your right side is not getting enough gas. I would pull the carbs and give them both a good cleaning. It could be a plugged idle circuit on the right and a good cleaning should solve that. Before someone suggests it, Seafoam or some other pour-in-the-tank carb cleaner may be good to keep a carb clean, but not to get them clean. A 30+ year old bike with 7900 miles has done a lot of sitting around.

After cleaning the carbs, set the the floats to 26-28mm (measured with the carbs upside down, the float tang just touching, but not pushing on the float needle, and measured from the gasket surface to the bottom, now top'cause they're upside down, of the carbs).

The throttle stop screw simply pushes the throttle plates open and prevents them from closing all the way. It is just there to set the idle speed.

After the good cleaning and the mixture screws back to 3 turns like you had them, sync the carbs. there are a few ways of doing it, but simply by sight is a good start. Download the .pdf manual available on this site and read it well.

Good luck! I have a '79 XS400 also and am just beyond the far eastern edge of that kingdom known as "Chicagoland".

 

[Bssoap74]

Thanks HoughMade,

I will try that once I get the Carbs off and time. Is there a how-to guide to rebuild the carbs and a how-to guide to sync them?

 

[HoughMade]

Look in the forum news and info section on this site and download the factory manual.