Starter run by it self

I just bought 1980 XS400 bike was very good condition I rode for 200 miles so far. but now there a problem i turn on ignition key and on switch not event press start button starter start right away and continue running while engine on I've to switch to off and try to keep press start switch in and out just in case it jammed inside. My question is if I disconnected wire from battery to starter switch would it stop this problem and Does it going to effect battery charging cause i don't know what would recharge battery is it from starter and I don't mind to kick start. I have wiring diagram that come with manual but I don't know anything about it.......any suggestion please help

Thanks in advance

So I'm trying to decipher what you are saying exactly.

-You put the key into the ignition and turn it on.
-you flip the kill switch to run
-your bikes starts up without you pressing the electric starter?

Did i get that right?

Try to take apart your kill switch assembly and see if there is any corrosion or if the starter button is jammed. If so, repair all that and then give it another try. Try even removing the starter button and spring completely and see if you still have the same problem.

Also do you know if your harness is original or if the previous owner chopped it up? If its chopped up that could be causing your electrical problem.

And to answer your question, yes disconnecting your battery will stop it from happening but then you will have no power at all. Unless your bike is wired all funky...then you've got a ton of other issues to worry about..

Thank Sly409....I will take it a part to see what happen. What is harness? that you have mention

and Yes you get it right

The harness is the main cable that all the electrical components are plugged into. Hmm I guess if you are new, you wont be able to tell if its been modified or not.

Start with the kill switch assembly and we'll go from there. Also, does it sound like your starter motor is winding when the bike turns on by itself? If it sounds like its just spinning, then thats a sign that the starter button may be jammed in the on start position or one of the contacts is stuck causing it to start right up when there is power.

so Sly409....can i put lubricate oil in start button to reduce jammed is that going to cause trouble

I had the same problem early in the spring here. I undid the black wire from the starter. and was able to drive successfully till my order of a horn button from Mikesxs came in. Then I was able to order a kit from Amazon for 15 bucks. I have not installed it yet, as I am trying to stomp out the oil drip gremlins. My electric start has been operational very sporadic. Lucky the bike starts on one kick if i remember to put the choke on, and the on switch to on to

Starter Motor Repair Kit for Kawasaki ATV KLT200 198cc 82-84 KLT250 246cc 83-85 KLF300 Bayou 290cc 86-88, Motorcycle KZ250 CSR 250cc 80-83 KZ440 LTD / Sports / Standard 440cc 80-83, Yamaha XS400 XS400S 392cc 81-82 SM-8203, 21163-1011, 4R4-81800-60-00 by Crank-n-Charge
Link: http://amzn.com/B004UASOWW

That company appears to be out of stock, so I used the 4R4 number on the bottom, for 27 bucks USD.http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=automotive&field-keywords=4R4-81800-60-00

If you tell amazon your bike info, it will tell you if this will work with your bike, also go to an OEM parts diagram, (partszilla, boats.net, or what ever you like), locate the starter number, and do a search with the work kit, Once you get a hit that on the right track, go to google, and do a couple more searches(click shopping) to see if you can find the best deal. for it. Don't forget to check your local supplier guy,(last) (Yamaha Boat/ATV/Cycle guy) He might be able to get it for a slightly more than the best price, but wont tack on shipping charges if He can get it. I was able to purchase a helmet at same price that was on a email 40% discount at my local Hitchingpost (here in MN) (thank you bikebandit)

got it figure out now after took it apart. there a piece of wire retention bracket loose and drop in there sometime it bounce and contact to switch wiring that cause short circuit and starter start....Thank for all your help