Help Starting My '81 XS400

[kasper]

Hey all this is my first post, iv just been having issues starting my '81 xs400. I bought the bike about a month ago and have put a bit of work into it already, though today was my first time trying to start it and i was unsuccessful. The things iv done so far are:

1) rebuilt the front disc brake
2) drained old gas and cleaned the tank out
3) oil change!
4) lubed up the clutch
5) cleaned carbs (just the float bowls though and anything else i could spray with carb cleaner)
6) put a little bit of oil in the cylinders (just a liiiitle bit)
7) put in a brand new battery

So today i tried starting the bike and it was a no go. I was kick starting, and i couldnt get it to start. i got compression in the cylinders, but no ignition. On top of that, a few things boggled me. The choke for one, id have to pull it and hold it, otherwise the rod would go right back into the carb.. is that the way its meant to be? or is there a way to pull the choke out and have it stay out? Im not too experienced with older bikes at all

The other thing was about the electric start. Id set the switch to "run" then id push the "start" button but nothing would happen. How is it supposed to work? The electrical on the bike seems to be fine, the headlight, signals, brake light and funny sounding horn all work. Realistically the evidence seems to point towards the spark plugs (i think), but i figured i might have been overlooking something really obvious. i know theres a wealth of knowledge on this forum and any input would be greatly appreciated

 

[Arclight88]

The new battery is helpful, but make sure it is freshly charged. Check that you have spark at the plugs (there are several posts on how to do this on this site.) If the plugs are getting spark, then provided that it was running before, the basic ignition timing is probably OK.

Since you are pretty sure you have compression, and if the spark plugs are firing, then it is down to ensuring the carbs are working properly. Your choke problem is a concern. Your choke should stay in the position you set it (it should not retract on its own!) Look at the videos on the basic operation of carbs by member BCWARE - they may help you out. You need to prepare to dismantle the carbs and remove the jets and clean them very well.

Keep us all posted and keep your spirits up. My '81 was in about the same shape yours is in back in Nov and now it runs great thanks to the fine advice and encouragement I received on this site.

 

[Onetype]

There are 2 little ball bearings that hold the choke in the 2 different positions. These are where the choke rod goes through the carbs (1 in each).

The start button has a constant hot wire coming off the starter relay (blue/white) to it once you turn the key on. When you push it in it grounds out and triggers the starter relay to power the starter motor. I would make sure your getting power to that, sometimes the contact beneath the switch also gets corroded.

 

[kasper]

Thanks for the quick reply, advice and encouragement! Ill be working on the bike again tomorrow, and will definitely be posting updates.

 

[HoughMade]

What position was the key in?

 

[kasper]

The key was in the on position, with the green light indicating neutral on.

I didn't have much time today so i just threw on some new spark plugs. Also cleaned the contacts in the boot but unfortunately she still didn't start! the plugs wernt giving me a spark when i checked them. To check them, i just popped them out, put the electrode head part of the spark plug against the casing of the cylinder and kicked away.
Just having thought about it, i was wondering if it could be the pickup coil? any thoughts on what else it could be?

 

[corruptmind]

did you try to short the starter relay with a screwdriver to see if it turned (basicly like sending the power from the battery straight to the starter)? My '81s was shot. My wives '81 had a bad TCI that was burned up for the left side due to bad fouling of the plug. Replaced the plugs and the TCI and she sparked on both sides afterwards. The manual shows you how to test the coils resistance with a volt meter to check if theyre bad. Make sure your frame is grounding aswell.

 

[63-Coupe]

I agree with trying to jump the starter solenoid first to see if that works. It's a quick and easy test.

On a parts bike I bought I was told the starter was no good. Before I stripped it down I checked out the starter and all that was wrong with it was the ground. The two bolts that held the starter in were snug but not tight. Tightened them up a bit and the starter worked just fine. The starter only has the hot wire to it and its grounds through its body. If you have a set of battery booster cables or something similar clip one end on the negative post of the battery and the other to the body of the starter, then try to jump the solenoid.

In my experience over the years often the problem lies somewhere in the grounding of any component that is not working.

 

[kasper]

So i did finally find my problem, though it only dragged on because ive been so busy with work!
I actually just did a continuity check with my voltmeter across the ignition components, though i didnt have to look long since my problem all along was that the contacts holding the ignition fuse were dirty! the voltmeter was reading as if there was no fuse there, and after cleaning the contacts the electric start started working, and the bike started up. it even idled for a bit haha. Simple as that! Atleast thats one piece of the puzzle solved.

 

[Arclight88]

Good find on an electrical gremlin! It is amazing the improvements that come from clean, fresh connections.

 

[kasper]

Good find on an electrical gremlin! It is amazing the improvements that come from clean, fresh connections.

Definitely! Who would've thought it was such a simple fix? Dirty contacts is one thing ill have an eye out for in the future, should any electrical problems arise again.