Carburator/ Exhaust Problems??

[kasper]

Hey all, so recently i was finally able to start up my 1981 xs400 after solving a minor electrical problem, although more problems have arisen since

Now one problem i have with my carburetor is that the choke doesnt stay out on its own, i actually have to hold it out myself. I assume that to fix that ill need to take the carbs off, and i havnt got around to doing that as of yet. My bike doesnt start on every kick, or every push of the start button.. its pretty finicky. What i find strange is that it starts up easier when i set the petcock to "pri" instead of "on".

The first time i started the bike, i used the electric starter and i was holding the choke almost all the way out. After hitting the throttle and keeping the choke out for about a minute i let it go back in and the bike idled fine. There was some leakage of exhaust fumes, especially at the muffler/ exhaust joint on one side but i imagine thats just a matter of swapping some old gaskets for new ones. Now heres the strange part. The next day when i was trying to start the bike up again, it didnt want to start. After numerous tries i finally got it to start but after a couple seconds (5-15 second i think) it would just die. It would die wether or not i kept the choke out. It was always gradual, you could see the rpms dropping as well as hear the engine winding down slowly. After i got off the bike i touched both exhausts and found that one was burning hot, while the other was totally cool to the touch.

This weekend ill be tinkering with the bike again and was hoping to get some input suggestions anyone?

 

[HoughMade]

There are some specific things to look at, but it sounds like the carbs need to come off for a thorough cleaning.

The choke rod has a small detent on the rod and there is a tiny ball bearing and spring on each carb that should allow it to click on halfway or all the way. If it does not click, the ball bearing is either missing, or so gunked up it does not get pushed into the detend by the spring...and these are tiny. So if you take it apart, be very careful.

If it runs better on Pri, than On, check the vacuum line from the carb boot to the petcock. That supplies vacuum that will pull open a valve and allow the fuel to flow when set to "On". If the tube is on and in good condition, perhaps your petcock needs a clean, rebuild or replacement.

Overall, sounds like dirty carbs that sucked in some gunk when it ran briefly. Again, time for a good cleaning, then an inline filter before the carbs.

 

[kasper]

Ill give it a clean this weekend, and hopefully that'll go a long way. I just put on new air filters before both carbs about two weeks ago. As for the ball bearing, i hope its still there and as you said, just gunked up. If its not there i guess i can always hold the choke out when im starting the bike.. though that will make kick starting it awkward to say the least!
I appreciate the fast response, and thanks for the advice!

 

[HoughMade]

Some have said that the ball in a grease fitting is the right size, if yours has gone missing....one of mine did.

 

[kasper]

This is my choke situation. I can clearly see the detents, and even the spring. Now where is the ball bearing supposed to be, at the end of the spring?

 

[HoughMade]

Yep, between the rod and the spring.

 

[kasper]

Some have said that the ball in a grease fitting is the right size, if yours has gone missing....one of mine did.

You dont happen to remember what size grease fitting you used do you? Would definitely be nice if the choke stayed out on its own!