My uncle's bike (1978 XS400) hasn't been turned on for about 2 years. It's in great cosmetic shape; only 3,000 miles; no rust. It was not stored properly in Chicago. It would not start. Replaced the battery, it would crank but not turn over. Then we cleaned the carbs and it started only with the kick start (after a few tries). It started once with the electric starter.

The problem now is that it idles weird. We adjusted it to idle around 1,500 RPM but when we roll the throttle (in neutral), the RPM would stay high (around 4-5k RPM) and would not go back down to 1,500 RPM. As we adjust the idle screw, the RPM would drop then stall. NOW it won't even start, nor would it come near to starting. We don't know what to do next. If anyone has any suggestions, let us know! Thanks.

Sounds like your adjusting the wrong screw, if you adjust the mixture screw this is exactly what will happen, On my Yam the Idle screw is underneath the carbs.

Hope this helps.

Adam.

My uncle's bike (1978 XS400) hasn't been turned on for about 2 years. It's in great cosmetic shape; only 3,000 miles; no rust. It was not stored properly in Chicago. It would not start. Replaced the battery, it would crank but not turn over. Then we cleaned the carbs and it started only with the kick start (after a few tries). It started once with the electric starter.

The problem now is that it idles weird. We adjusted it to idle around 1,500 RPM but when we roll the throttle (in neutral), the RPM would stay high (around 4-5k RPM) and would not go back down to 1,500 RPM. As we adjust the idle screw, the RPM would drop then stall. NOW it won't even start, nor would it come near to starting. We don't know what to do next. If anyone has any suggestions, let us know! Thanks.

its an air leak or too much air getting into the mix.

mixture screw should be 2.5 turns anti-clock wise from bottoming out. check intake rubber for cracking