Carb slide does not have the same speed

Hi! I recently bought a Yamaha XJ750 SECA, and this group has been incredibly helpful. Thank you for that!

I took the carburetor off the motorcycle to clean it (the tank was full of rust), and now it’s running again. I noticed that it’s slow to return to idle after giving it some throttle. I took the carburetor off again and saw that the carburetor slide doesn’t drop at the same speed. However, when I take it apart, I can’t see why. Could it just be that the spring is old? Any tips?

Also, it smelled a bit burnt when I started it up. I only had it running for about a minute, and there was no smoke. Is that normal? It hasn’t been started in 10 years.

Thank you so much for the help—it’s greatly appreciated!

 

Welcome to the forum.

Yes them carbs need to be really really clean. Did you follow the "church of clean" that can be found in the upper right hand corner of any page. Take a look a the diaphragms and make sure there are no small holes or tears in them. A lot of times just running the bike a little will take care of that one carb hang once you sync them and get them dialed in.

A little back history of your new bike?

What did you do to the tank to make it all clean and get rid of the rust? I hope you are using a in-line fuel filter after all your hard work cleaning them carbs. No matter how clean the tank might seam, always run a filter.

 

As @Timbox said, diaphragms. Also check the springs are all the same, the o-rings at the top (ooo - do Hitachis have the little o rings?), then the springs all the same, the little hole that transfers the vacuum from under the piston to the underneath of the diaphragm, and lastly the bore the slide sits in, and the slide itself. Do not use sandpaper...
If this hasn't run in 10 years you will likely have blocked starter jets at least, plus a load of other issues.