xs400f (2L0) resuscitation +

ANUBIXS400

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Hello all,its been a while but Im hoping to share some of the details this project, listing out what i can (my brain likes this method) and taking some hopefully decipherable photos.
So far:
Compression @ 140 / 135 - seems pretty low to me, I have these readings pre-tear down and ordered some new rings / seal kit / gaskets as Im trying giving the bike some attention and it needs it.
I haven't taken the head off yet although engine is out of the frame (pretty much everything striped except engine) as there's so much rust / touch ups to deal with I'm just starting the project again.

Life support =
front brake caliper piston - was seized and pitted - buy part - maybe rebuild kit?
steering tree bearings - heard the tapered ones are the way to go (research needed)
oil filter - standard -
air filter - # 1L9-14451-00 - (original could be difficult to find) - make some?
Carbs - need a scrub + butterfly seals(how can i tell?research) Float bowl gaskets, rebuild choke
Spark - right side thread stripped (get thread insert), new plugs / caps / wires (which type?research)
Battery - f#$ked.....or maybe not (was new 4yrs ago)
Neutral indicator switch seal - O-Ring - # 93210-29196-00

Was wondering if anyone thinks is 140/135psi passable?
If I put new rings in, is it best practice to hone the cylinder walls first or can skip it?
 

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Welcome. I strongly advise against tearing into the engine when it seems to be functioning as normal. Those compression readings are good IMO. If the bike idles, its probably OK. Theres still lots of life left in that engine. Headgaskets leaking a bit of oil is fairly common and an easy fix.

spark plug threads can be repaired, or you can buy a good used head easily. Toss that old battery to the recyclers.

I would upgrade to a tapered bearing setup on the front forks and bronze swing arm bushings for the back. Also consider upgrading to progressive fork springs, slightly stiffer and actually have some rebound. Old forks get saggy and soft.

Theres lots of info on carbs, basically just clean them about 8 times and replace the seat and needle.

Caliper rebuilds are out there.
 
125 is the low end for compression. High end is 155. A valve adjustment and some oil changes/running may bring them up a bit more.
 
Almost got it back together now. Try to start with a temporary gas tank but no luck.

Figured out my handle bars weren’t grounded which was the problem with the electric starter. But it still won’t go, maybe I need a new battery, I just replaced some of the battery acid and the charge was getting To 13.5v but dropping down fairly quickly when turned on.
I can’t remember how much power it needs to get it fired up?

carbs have been hand cleaned, new air filters and new plugs. Guess the the sensible thing is to go get a new battery. I was hoping it would fire up but I think it needs more power.
 

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My battery has been fairly low for a while, just holds a "surface" charge but the kickstarter has reliably started her up every time. Runs like a 70's scalded cat. If you're needing to do forensic startups hook up a car battery.
 
No luck there. I got the battery hooked up and had the electric starter turning over and nothing.
I have fuel and spark so possibly a power issue? Or I need to play with carb adjustments?
When I first tried with the kick start it spluttered a little bit and I thought I’d have it going shortly but I got nothing. Took the air filters off and it looked wet in the boot.
I’m thinking it’s maybe the battery not having enough power, I believe these bike are very sensitive with the voltage/amps but now I feel I know very little.
Any suggestions would be much appreciated.
 
At this point perhaps switch the leads from the coils? It's a 180 twin and when I first put mine together I had them wrong, switched the leads and VROOM!
 
Thanks for that, i checked them and they were reversed. I got it started! once haha. now its back to nothing. I noticed gas leaking out of the left air filter, so that sucks. Took the carbs off and checked float height - it was a little high, brought it down to 32mm but its still leaking probably a combination with petcock as its old. Also head light isn't working but not sure if that would stop it starting.

if there is too much gas coming out i guess it will not fire because of the air/fuel ratio. maybe ill lower floats and see if that works other than that I'm stumped
 
I've done some reading (uh oh) and it seems I should try the floats at 26mm +/-1mm rather than the 32mm I got from the manual. This might reduce the flooding. Ill also turn the mixture screws out 3 turns (had them 1.5 before)

Recap: (for anyone searching posts)
Leaking / flooding Carbs (I had fuel dripping from air filter)
Check float height - brass 26mm
float needle - check for wear (rings on point)
float needle seat - check washer and screw back in position firmly
floats - check for leaks/pin holes (submerge in liquid see if they fill up and sink)
petcock - check if it leaks when disconnected. clean/inspect


If i had a pressure tester i would hook it up to the fuel intake and apply pressure to see if the needle or seat leaks (with light pressure holding floats down), this would be a sure way to diagnose it as the problem.
 
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At this point your plugs are most likely fouled from all the flooding. I would get a fresh set and start with the proper carb settings.
 
I hear that. I got a fresh set on and adjusted carbs. It fires up now! Very happy about that.

the bike dies when I switch the headlamp on so I need to figure that out. I’m looking at the wiring schematic for the US F model and my headlight on off switch is on the right handle bar. But wiring doesn’t show that.
Anyway maybe the headlight draws to much power from an old battery so it shuts it off, but I’m thinking it’s more likely shorting somewhere. I’m not very experienced with electrical stuff, so I’ll see what I can figure out here.
 
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So far I’ve detected that a separate blue wire (the other 4 wires go to a terminal) coming from the right handle bar switch is the culprit.

I’m really not sure what’s going on with it, but it stops the engine as soon as it’s connected to the blue wire that go to the harness. So my hillbilly remedy is to just connect directly to the headlight, I can use the on/off switch but I have no high beam just low. This is fine for now as I only have so much time to be tinkering.
I’m a little embarrassed about the birds nest of wires in the headlight housing but still managed to get it back on with everything working ! I’ll get some pictures this week.

need to figure out the seat now...
 

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