Wont idle right.

[FargoBones]

Just bought a 78 xs400 2e, took off the carbs and cleaned them really well, put new gas in, changed the oil, replacing air filters tomorrow, and cleaned the petcock. I can get the bike to fire first kick, idles for a bit, but as soon as i touch the throttle it dies. What other things havent i done?

 

[Under Dog]

You don't mention whether or not the choke is on or off???

Will it idle without the choke? I was just there on my '80. Had to take the carbs apart about 3-4 times before I was intimately familiar with each passage and absolutely certain everything was clean (carb cleaner and compressed air are you're best friends here). I swore up and down my carbs were clean, but the bike the bike would only idle with the choke on. ??? Turned out my air screws needed adjusting. Manual/factory stated about 1 turn from lightly seated. The little o-ring was so mis-shapen on mine that I'm currently at 3 1/2 turns out and think I may be running a little lean still. Check your air screws, that might help.

Otherwise, sounds like the pilot jet may still be clogged up. What kind of crud is in the gas tank/fuel line? Could be a clean carb that picked up more junk from the tank?

 

[FargoBones]

The bike idles real high with the choke all the way out, and idles almost perfect with the choke all the way in, i drained all the old gas and was yellow as pee, replaced it with new gas and still the same thing. I am not familiar with bikes at all this is my first one, I will have to look into syncing up the carbs and taking them apart a little more to get down to the core of the problem

Thanks for the advice keep them coming

 

[akronevan2]

Have you let it warm up? In my experience, mine will do about the same thing, but after I let it warm up everything is fine. Good luck.

P.S. Seafoam is great at keeping your fuel system clean.

 

[drbone641]

+1 on the Seafoam. Just keep running it with a good cleaner additive. My sons was doing the same thing and the more it runs the better it runs. 2 or 3 tanks and no problems.

 

[bcbobbers]

Agree with the checking of the air screws. Those rubber o rings on the screws are often dry rotted away or so mis shappened that they look and the bike runs like crap. If that is the case I know people on here have bought the ones off mikexs with good luck. Also the air screws need to be adjusted to 2 1/2 to 3 1/2 turns out instead of 1 turn out like the manual. I think everyone on here will agree that the specs on the manual are wrong and were made that way for environmental reasons, the bike will run much better at these specs.

 

[OnePhate]

another +1 for the seafoam, I bought a 82 seca with the same issue for 400 bucks, 12k miles, all because it wouldnt run with out the choke on. I seafoam'd and it ran great until i sucked rust into the carb.

 

[kaptainkevo]

I also have an idling question, dont want to start a new thread but i just got my maxim home, and havent really fired it up for very long, but one thing i noticed is once it started to warm up a bit the rpms seem to go up and down a bit from 1000 to 1300 or so, is thjs maybe a timing issue or should i just try to warm it up completely and see if it evens out?

 

[Scorpio1963]

I think the idle jets are are in the venturi of the carbs.They are some kind of airjet anyways and if the holes are plugged up your bike wont idle correctly.Take them out if you can,sometimes they are very difficult to remove.Take a very small needle,like the smallest sewing needle you can find and poke it through the hole.Becarefull you dont strip the heads on them.

 

[kaptainkevo]

I warmed it up completely to see how it would do, after warm it idled smoothly, but high. Easily fixed.