81 xs400 poor throttle response and overheating

[mtberbob12]

I have an 81 xs400 that I recently got running again but am having trouble getting it to run good. I got it to idle but it seems like it is idling pretty high,I can't check as I don't have a tach. It also gets very hot very quick but trying to richer the mixture doesn't seem to help. Also the throttle response is pretty slow and when you ride it or rev it up it seems like the throttle sticks for a little bit it gets worse the higher the gear your in. I have cleaned the carbs enough times to say it ain't dirty anymore and there are no vacuum leaks that I could find. Any help would be greatly appreciated.

 

[Scorpio1963]

You cleaned them but did you sync them?

 

[markjs]

Yes, that and also by what method do you clean? These carbs have lots of fine passages and anything short of soaking or boiling can often prove insufficient. Another thing you will want to look at is the condition of the diaphragms. Really sounds like a carb problem to me.

 

[mtberbob12]

I have synced the carbs and I have had the carbs apart all the way and used carb cleaner degreaser and compressed air to clean out all the passages and jets. The diaphragms are fine I have held them up to the light and don't see any cracks. Idle screw is all the way out so I'm not sure why it is still idling high

 

[markjs]

My butterfly was actually stuck open when I got my bike. I know nothing of air screws, those have long been illegal in the states and so few bikes I have owned had them so I can't say. Still did you remove the jets when you cleaned and blew it out? They really need a full disassembly to be clean, just some carb cleaner though the jets won't often cut it. You got to unscrew all these little jets, clean and blow out the passages. If this is something you didn't do, much as it sucks, I'd pull it all apart and boil them in vinegar and water. I tried just doing the jets and the bottom, but it wasn't right until I did the full meal deal on my carbs.

 

[mtberbob12]

I had it completely apart even though all the jets and needle are brand new, it runs just idles high and runs lean, I also set the float height recently and that helped to idle rigt without shooting fire from the exhaust but it is not a perfect fix

 

[Scorpio1963]

Hemmm mine shot fire out the exhaust after rejetting also but this was before I fine tuned everything.I agree with markjs.You idle screw should be all the way out and adjusting the butterflies should increase idle.On the airfuel jets how many turns do you have them adjusted to?A rule of thumb is 21/2 turns then fine tune from there.What size jets are in the carbs?

 

[mtberbob12]

I have the screws the recommended 3.5 turns out. Of have to look and see I can't remember it off the top of my head but it is the jet kit from mikesxs. Is there a way to adjust the butterfly's both at the same time instead of opening one while closing another?

 

[jmd_forest]

Check the timing and set to spec if necessary. Could be the source of both poor throttle response and overheating.