81 xs400 died on throttle

[KoryGable]

I have a 1981 xs400 that ran perfect for about 6 months and one day started dying on throttle.
It idles ok but not as well as it should.
I rebuilt the carbs, checked all the wiring, petcock, vacuum hoses... everything. Still died on throttle.
Can anyone help me?

 

[Scorpio1963]

What is your idle speed?Maybe its too low.It should be 1200 warm.Did you sync the carbs after rebuilding them?

 

[16VGTIDave]

Sounds like you need to get into the carbs again. Dirt or corrosion can plug the tiny passages. And it can be a pain to get clean.

Any unusual noises from the engine? I'm wondering if the timing chain may have jumped a tooth...

 

[KoryGable]

I thought it might be the timing chain but reading up on the 81s I cant figure out the right way to adjust the timing. Can you send me to the right place to help me with that?

The carbs are clean 100% i just had them off and went over them thoroughly

 

[KoryGable]

The Idle speed is fine

 

[abobber91]

Make sure that when you cleaned the carbs that you took out the main nozzle jet and shot compressed air and carb cleaner through the connecting passages. Its the biggest piece of brass that runs down the middle of the carb. you have to push it out with a pencil or something. This piece seems to be over looked often because it doesn't always easily come out. Thought my carbs were spotless until I figured out how to remove it, it was very dirty in there.

(Mentioning this because I'm pretty sure the bike idles off the pilot jet and takes throttle from that main jet and its nozzle jet.)

 

[Scorpio1963]

One thing I found in my carbs was the air jet in the venturi can hide dirt pretty well.I did a thurough job cleaning my carbs and decide to remove those jets.Although it looked clean when I took it out I seen it was plugged.I stuck a small needle in it to push the crud out.So you might want to check them.

 

[16VGTIDave]

Nah, that can't be it. He said his carbs are 100% clean.

 

[abobber91]

A common mistake i made many times was thinking my carbs were clean enough..

Just because you can't see it doesn't mean its not there. lol

 

[arfstrom]

You know the thing about having a bike that runs for 6 months, and and having a 100% Clean carb. doesnt mean anything if you don't have a paper inline filter protecting your investment.

Now this web site, http://www.amckayltd.com/carbguide.pdf only disappointed me, cause all the good pics are at the back. but it seems to be meticulous. Since I didn't read all of it, cause I know my carbs are 110% clean with inline filter. (If I am not mistaken our carb is the BS-34. Of coarse I found an suitable link, listed under the Tech tab on top of the page. http://www.xs400.com/tech.php, under Carb, But it doesn't' list everyone favorite way of boiling there carbs. I like to use Lemon juice. I think the next time its cheaper to use vinegar. so just look up Boil in one or both the search lines on top of this page. There are a ton of us that have. There are a few that can do the ultrasonic. Whatever you decide. I suppose as long as your going in there again, check your floats for fluid inside the float. that's how I discovered a bad float.
Tobie

 

[Scorpio1963]

I have tryed boiling carbs in viniger and lemnjuice with very limited results.Chem dip is the besy way to go imo.Also drain your tank you`ll never know what you can find laying in the bottom.I was surprised my tank had alot of crap in the bottom.An inline filter is a must imo even though there is screen on the pitcock inside the tank.That was also crusted over with varnish.

 

[Scorpio1963]

Exactly I had went through my carbs twice and they looked spotless.It wasnt till I decided to rejet when i discovered I missed the dirt.When it was mentioned to me clean your carbs and reclean them I thought this is an over exageration but not so.

 

[arfstrom]

Been there 2

Yea wheather you dip/or boil, and blow tons of air, one of the hall marks has been the three streams from near the butterfly. I haven't seen mention of that recently, but when you pull out all the jets, pins, and rubbers. Single people will boil carbs in the house, the happily married guys will boil carbs outside, Some will boil for hours, some will boil for 20 minutes per side, I remember after my 2nd cleaning going under the diaphragm, and pulling out what looked like a rubber silicone plug. I remember finding a bug there too.
Good luck

 

[Scorpio1963]

Interesting analogy on being happily married.My wife is happy and I am happy and we are both married but yet when I have boiled parts its been in the kitchen.Now when it comes to burning stuff the wife does that in the kitchen but I do it out in my make shift garage the utility room

 

[arfstrom]

I guess I haven't dared to go there haha I always figured, my signicant other would Shoot me.

 

[16VGTIDave]

She may just! And if yours is anything like mine, she would start with your toes and work upwards with every shot until you swore to never, ever, do it again!

 

[Scorpio1963]

Well I have a very cool laid back tolerant lady which I might add is 10 years younger than me.We been happily married for 10 andhalf years.