1980 XS400

bbsquad11 · Oct 5, 2018

Hello,

I'm new to the motorcycle world. My first pick up is a 1980 XS400. I can't seem to get it started up.

Seems to be leaking fuel out of one of the carburetors.

I have attached a video and maybe any of you could possibly lend a hand helping me figure this out.

I am mechanically inclined in auto motive

BBS360 · Oct 5, 2018

I don't know what the video is supposed to show other than one failed attempt.
A bike needs fuel, air, and sparks.
Problems with any one will keep you from starting.

See this thread:
http://www.xs400.com/threads/how-to-what-to-do-first-with-your-new-xs400.10595/

Remove and clean the carbs.
Thoroughly.
But do not destroy rubber parts in the process.
Preserve or replace the butterfly shaft seals.
Fix the leak. Could be the carb floats overflowing.

Check the rubber carb holders for leaks. Even cracks that look minor can suck air.

There are tons of past "my bike won't start" threads with various other tips. Lots of resources in past posts.

bbsquad11 · Oct 6, 2018

BBS360 said:
I don't know what the video is supposed to show other than one failed attempt.
A bike needs fuel, air, and sparks.
Problems with any one will keep you from starting.

See this thread:
http://www.xs400.com/threads/how-to-what-to-do-first-with-your-new-xs400.10595/

Remove and clean the carbs.
Thoroughly.
But do not destroy rubber parts in the process.
Preserve or replace the butterfly shaft seals.
Fix the leak. Could be the carb floats overflowing.

Check the rubber carb holders for leaks. Even cracks that look minor can suck air.

There are tons of past "my bike won't start" threads with various other tips. Lots of resources in past posts.

Hello,

Thank you. Your are right. Sorry for now looking harder.

Here's an update.
I used starter fluid sprayed a bit by the air intake and it turned over.
I notice it seem to be only running on one cylinder. The other I assume is not because it flooded with fuel from the float.

My intake boots need to be replaced; I can see cracks. I did notice something that one air outlet was plugged and wasn't sure if that was how it is?

BBS360 · Oct 7, 2018

The other end of that tube should attach to the fuel petcock.
It activates the fuel flow when the engine is running.
If it was not attached that cylinder would be running very lean.

The rubber diaphragms in the stock vacuum petcocks tend to deteriorate but assuming it is working just plug the tube back into it.
Some will replace the stock petcock with a manual one, requiring it to be manually turned on and off.
If that is done then the ports on both carb boots need to be capped.

bbsquad11 · Oct 8, 2018

BBS360 said:
The other end of that tube should attach to the fuel petcock.
It activates the fuel flow when the engine is running.
If it was not attached that cylinder would be running very lean.

The rubber diaphragms in the stock vacuum petcocks tend to deteriorate but assuming it is working just plug the tube back into it.
Some will replace the stock petcock with a manual one, requiring it to be manually turned on and off.
If that is done then the ports on both carb boots need to be capped.

Thanks alot!
I'll be taking a further look into this tonight after work. I'll keep you posted how it all goes.

bbsquad11 · Oct 9, 2018

Okay,
So I removed the carbs tonight. A few things I have notice comparing to other videos I’ve seen on YouTube.

Am I seem to be missing some parts. Let me know if I am. Here’s a video of the bowl being removed,

Here’s a closer picture.

I also removed the diagram and these were the order I took em out. Anything missing?

BBS360 · Oct 9, 2018

I have an earlier and later version of the carbs but I think you're ok.
Did the needle part of the float needle valve come out with the float? Didn't see it.
Should look something like the part on the left:
https://www.mikesxs.net/float-needle-valve-assembly-xv920-xj750.html
Might be brass. Might not have the wire retainer.

bbsquad11 · Oct 9, 2018

BBS360 said:
I have an earlier and later version of the carbs but I think you're ok.
Did the needle part of the float needle valve come out with the float? Didn't see it.
Should look something like the part on the left:
https://www.mikesxs.net/float-needle-valve-assembly-xv920-xj750.html
Might be brass. Might not have the wire retainer.

Yeah the float needle came out with the float, it was still attached. However, what is the other part on that link? My first image it doesn't have anything in that hole.

BBS360 · Oct 9, 2018

Wasn't the best picture to choose.
That other part is the hole. Yours doesn't thread in, it's retained by the forked piece with the screw.

spectra · Oct 10, 2018

Also take that forked piece off and pull the tube out a there is a filter at the bottom to clean.

Carbs dont look to bad. But as they say clean, clean and clean again...........

bbsquad11 · Oct 10, 2018

I will re assemble it tonight and see how it goes...

xschris · Oct 10, 2018

Make sure to remove the pilot jets and the emulsion tubes ( needle jets) I would replace all the o-rings, gaskets, rubber pilot jet plugs and needle valve.

bbsquad11 · Oct 10, 2018

Probably my mistake on this... I ordered a rebuild kit from ebay... aka China... and half parts i got looked completely different size wise. =(

bbsquad11 · Oct 10, 2018

sizes were different. Im assuming that this kit I received was for a 78-79.

i figure i would throw it all back together; and attempt to start it. Now im getting nothing at all from my electric start or kick start...

BBS360 · Oct 10, 2018

Yeah. That pilot jet won't do anything for you.

Be careful with carb and especially brake parts from China.
Cheaper isn't always better.

spectra · Oct 11, 2018

Yes when it comes to parts cheaper is not always better.......I found the K&L kits to not be so good.....I just bite the bullet and order from Mikes or Sirius there a little cheaper.

NewHavenMike · Oct 11, 2018

The kits that Sirius offers are pretty good. You get most of what you need. I used them for my carbs. When it comes down to jets, I use Jet R Us for that. There, you can get pretty much any main jet you would need. They have some pilots and needles but they probably wont be exact.

Once you get part numbers, things are easier. From there, I like to search the classifieds here before anything else. I also search EBay by the part number. I just came across two brand new unopened needle jets for my 360s carbs, I probably wont need them for a while, but I have them for when i do.

ALWAYS order genuine Mikuni jets. The aftermarket ones are drilled differently and have a huge affect on jetting. I compared a mikuni jet to an aftermarket one using a visual comparator at my work. The aftermarket jets are about 8 steps smaller than whatever size you choose from the mikunis.

bbsquad11 · Oct 11, 2018

Hey guys,

Thanks for the all the input. Definitely going to tear this apart again and order the correct parts from MikeXS. Hopefully that will take care of the carb issue.

After all of this I'll have to look into the electric start. I took it apart last night and saw the connector broke off. I attempted to solder it back on but still no fire. So I'm assuming my next option is to check voltage points from starter and rectifier. My Three fuses seem to be good. Battery is a bit low but keeping a charger on it.

bbsquad11 · Oct 17, 2018

Hey guys.

It’s been a bit. But I’ve been sorting out the wiring. Had a question where this, this is how I found it. Red & black is signal. Green/yellow is brake switch. Not sure where the black to two yellows go? Looks like the previous owner was trying to do something .

Need help figuring where these plugs go into if they’re needed as well.

Thanks again.

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