New XS400 owner and member

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bcXS400-81

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Hey all,

Thought I'd start a thread to introduce myself and maybe follow a bit of my build(s) as they progress. I recently picked up 2 1981 XS400's for really cheap, one runs but doesn't charge and the other isn't running but is basically complete. I come from a sportbike background and don't have much experience with motorcycle mechanics other than just general maintenance. I've been wanting to pick up an older bike, specifically an XS650 or XS400 for a while as I've really been inspired by some of the bikes by Gravel Crew, Wrenchmonkees and Brat Style. So thats going to be the theme of my builds.

It looks like there's quite a knowledge base here, so I'm looking forward to learning from all of you.

I have a couple quick questions off the bat;

First, whats the best source of parts for these bikes? They obviously don't have the following or support that the XS650's have, so I've heard parts are hard to come by.

Secondly, how reliable are these bikes? I've heard pretty mixed reviews so I'm hoping I haven't bit off more than I can chew in adding 2 of these things to my garage.

I'm hoping to begin the teardown on the running(ish) bike soon and try and diagnose the charging issue. I've got the Haynes manual, which details a pretty decent diagnosis procedure for the charging system, but any other tips or tricks are greatly appreciated.

Thanks Guys!
 
Welcome! Glad to have you here! The bikes that you're planning on taking inspiration from are some of the best around, so I'll be watching to see where you take it. Sounds like a great idea to me.

You have came to the right place for information! There are several people here that know these bikes like the back of their hand. You're right, the little 400's don't have near the following of their big brother, but that's the fun part.....you can make the bike the exact way you want, and don't really have to worry about someone pulling up next to you at a red light on the same bike! Parts may be hard to come by at first, but after a little research here and maybe a few nights surfing the web, you will find most everything you need. Ebay will become one of your best friends. haha

Reliability really isn't an issue as long as you keep up with the bike. Coming from a sportbike background, let me warn you now that this bike is a totally different animal. An older bike needs a little more love than a new, fuel injected crotch-rocket. I'm not biased away from sportbikes, I would have one if the insurance wouldn't rape my wallet! I'm just trying to let you know that these bikes will be much different. As long as you keep up with regular oil, plug, bearing, etc. changes, the bike will last as long as you want it to.

Having a manual is a good idea. Be sure to post what you find on the charging system when you dive into it, so we can help! Looking forward to hearing more, and sorry for the HUGE post!! haha
 
bloody Hell HT77, your in a good mood. LOL.

Welcome bcxs400, they are great bikes and very under rated ATM. But, they are getting more popular and as such parts are getting more expensive. I've bought stuff on ebay years ago for peanuts, now the're monkeys!!

:stupid:
 
Last edited:
drewpy said:
bloody Hell HT77, your in a good mood. LOL.

Welcome bcxs400, they are grweta bikes and very under rated ATM. But, they are getting more popular and as such parts are getting more expensive. I've bought stuff on ebay years ago for peanuts, now the're monkeys!!

:stupid:
Click to expand...
It's early....and I'm drinking a MASSIVE cup of coffee!! hahahaha
 
Ok, so I've finally had time to dig into my bike in the last month, after pretty much a year of it sitting in my garage.

I've got a few questions as I get into this:

1. It looks like the alternator wires were pinched between the sprocket cover and engine case, one of them is frayed pretty bad and almost broken in two. The PO said there was a charging issue with the bike, so I'm thinking this might be part of the problem. Can I just solder in some fresh wire? It looks like the stock wires have some sort of heat resistant fiber wrap on them, so I dunno if I need special wire?

2. The bike has a pretty gnarly oil leak, which after taking off the sprocket cover looks like it might be coming from the oil pressure switch unit (I'm hoping that's where it's coming from, atleast). Everything was coated in oil and road grime so I drained the oil and cleaned everything up, I'll be throwing fresh oil in it to see where the leak is coming from. What size socket do I need to take this thing off? All i know is it's bigger than anything I have haha. Also, if it isn't leaking from the pressure switch, what's the most likely place?

3. The gear shift selector/rod has some lateral play in it. Is this bad? Could I possibly be leaking oil from here?

4. Compression test: what's the best method? I have the carbs off right now, can I do a compression test with them off? Seems to me it shouldn't matter what's happening either side of the valves as long as they are sealing. That said, I've never done one before.

Tomorrow I'm hoping to get the carbs cleaned, do a compression test to make sure all is well internally, and throw some fresh oil in it to see if I can pinpoint that leak. Thanks for the help!
 
Here's where I'm at:

teardown.jpg


great lighting, I know :laugh:
 
Welcome!
Oil leak from oil pressure sensor would be simple fix once you determine where. Other places under that sprocket cover, the neutral indicator and clutch rod seal. Don't mistake "oil" and grime and stuff for an oil leak if it is chain lube. Once cleaned up you'll find out easily from where though.

bcXS400-81 said:
Hey all,

I have a couple quick questions off the bat;

First, whats the best source of parts for these bikes? They obviously don't have the following or support that the XS650's have, so I've heard parts are hard to come by.
Click to expand...
Some of my more used bookmarks, haven't shopped from them all but still use them for reference, part #, superceded #, prices. .you get the idea.

http://speedandsportinc.com/
http://www.nwvcp.com/pages/OemParts?aribrand=YAM
http://www.yamahasportsplaza.com/pages/OemParts?aribrand=YAM
http://www.kahunapowersports.com/fiche_select1.asp?cat=Motorcycles&mfg=Yamaha
http://www.powersportspro.com/pages/OemParts?aribrand=BRP_SEA#/Yamaha/XS400_-_XS400H_-_1981/ELECTRICAL_2/XS400H_%281981_MOTORCYCLE%29/ELECTRICAL_2_%28XS400H_-_1981%29
http://www.yamaha-motor.com/sport/myyamaha/prompt/L3Nwb3J0L3BhcnRzL2hvbWUuYXNweA==/Parts%20Catalog/starthere.aspx
http://www.partsnmore.com/parts/yamaha/xs400/?filters[fitting]=custom
http://www.mikesxs.net/
http://www.midamericamotoplex.com/fiche_select.asp

And of course ebay for sure!
So there are a few, - do you want more? The last one was to point out it doesn't hurt to have your local (somewhat local) dealer to check if they can get stuff. That place they are cool; i've heard others say the dealer scoffs at just the idea of bothering with helping you. They want you to buy new, you're wasting their time, etc.. I've had that exact experience at a different city but ownership has changed so maybe their attitude has too.
 
don't over tighten the pressure switch, its tapered and will crack the block there.

check out my blog for rewiring the stator, pretty easy.
comp test better off with no carbs, need it to be open there. try dry then wet with a little oil.
 
Thanks guys,

I spliced in some new wire for the alternator harness, should be atleast a temporary fix for the frayed and exposed wires.

Compression test results (dry): 150psi on the left cylinder and 120 psi on the right. Are rings in my future? Or do you think just adding oil will bring the compression up on the right? As this is my first go at working on bikes, I was really hoping not to have to pull the engine haha.

Haven't had a chance to source a socket to pull the oil pressure sensor, but as soon as I do and eliminate that as a source of oil leak, I'll fill it with oil and try another compression test.
 
bcXS400-81 said:
Haven't had a chance to source a socket to pull the oil pressure sensor, but as soon as I do and eliminate that as a source of oil leak, I'll fill it with oil and try another compression test.
Click to expand...

For the wire to oil sensor can't you use a 7mm wrench, socket or even stubby screwdriver?
And the oil pressure sensor itself, why a socket or special tool? Channel locks and if you don't want to any damage indent scratch marks use a shop towel and the channel locks and lefty loosy :)
 
bcXS400-81 said:
Thanks guys,

I spliced in some new wire for the alternator harness, should be atleast a temporary fix for the frayed and exposed wires.

Compression test results (dry): 150psi on the left cylinder and 120 psi on the right. Are rings in my future? Or do you think just adding oil will bring the compression up on the right? As this is my first go at working on bikes, I was really hoping not to have to pull the engine haha.

Haven't had a chance to source a socket to pull the oil pressure sensor, but as soon as I do and eliminate that as a source of oil leak, I'll fill it with oil and try another compression test.
Click to expand...

if the bike has been standing, it could be just sticky rings. An Italian service will cure that!
put oil in the 120 psi one and see what reading you get. if the psi rises significantly, then its rings and do as mentioned, if no change look at the valve seats/adjustment.
 
Ah yes. The dreaded lambo cancer issue. Those are famous for gumming up if you don't drive em in triple digits regularly (imperial speedometer)
 

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