New 79 owner

esupak

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Howdy.

Just bought a 79 XS400F off of one of my friends. The bike has been sitting in an unfinished part of my apartment for about 2 years, so I finally just asked if she'd like to sell it. The bike has 7700 miles on it, and is in pretty decent shape other than some minor rust and some bent accessories (Bike was blown over by wind twice while in possession of the PO). It rides pretty decent, but has some vibration at high RPMs on the road.

The headlight bucket was also crushed, so I got a plain Lucas style 7" headlight bucket from Mikesxs (these guys are fast). Still need to pick up a new headlight (wish you could see me trying to put the stock headlight into the new bucket :confused:) I noticed that the new harness for the headlamp contains 3 (Blue, white, green) wires while the original setup has 4 (Black, Green, Yellow, Yellow). What is the proper way to wire this harness (Ive done some searching but haven't found anything yet)? Will the 7 inch headlamp draw more power than stock? Also the bucket is longer than stock and I am concerned about the clearance with the stock headlamp mounts.

Indicators are bent from its experience with the wind. The washers next to the mounting gaskets are bent as well, but i might like to replace these with signals that are smaller and closer to the frame.

The tail light works fine, but I think it looks absolutely horrible. Any suggestions on a replacement?

Tires seem pretty good, made in May 04' judging by the codes....still lots of tread and no rot to my knowledge.

The brakes leave a lot to be desired. Front works decent and rear barely....new pads are in route.

I put some gas in it and it fired right up, no problems. The right hand cylinder doesn't seem to be running as strong as the left hand cylinder. The carb holders look like they have been patched with some sort of silicone, so I am suspecting they may be an air leak. I plan on testing these with some starter fluid. Carbs will definitely need cleaned and synced.

I plan on checking valve clearances, timing, carb float level (26 or 32mm?)

The oil gives off a slight hint of fuel, but just bought some Oil and received a new filter and o-ring set.

Chain was a bit loose, so I tightened it the other day to about 1.5 inches of deflection.

I plan on changing the front fork oil. Seems to me like a large syringe is the tool to use for fluids. Any suggestions on a good model?

Ive taken off the passenger foot pegs, engine guard (bent as hell) and chain cover so far.

Eventually I plan on using some K&N pods with minimal exhaust (not open pipes, but the next step up). Ive read of people going up 2 sizes with the jets and raising the float needle, does this sound right? Any suggestions on a good exhaust for a decent price? what size pods would i need for a 79?

Looking forward learning as much as possible from this forum and returning this bike to a mechanically sound condition.
 

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if you do test..please post the output..im curious, on mine i get 13.5 v at 3k revs..its not enough to charge
 
Congrats, I just picked up a 77 today. Got my work cut out for me. It is not " not ready to ride" as the guy who sold it to me had it listed. But hey, working on it is half the fun.
 
On the tires, they are probably your highspeed vibration. Old tire = bad tires. Get new ones and use Dyna Beads for balance.
On the headlight, the bike wiring, the black is ground, the green is low beam, the yellow is high beam. The other yellow is either the wire to the high beam indicator or the front brake switch.
On the new headlight It should have three prongs on the back, the same as the srock bulb, so the plug that was in there for the old will plug on the new. I think the green is ground the blue low beam the white high beam. Not hard to check just hook it to a battery. On the rear of the bulb it shoulkd have three prongs, two verticle one horizotal on top. As you look at it ground is the right verticle prong. Low is the top, high is the othewr verticle.
A headlights current draw is not determined by the diameter, it is determined by the output in watts. Most H4 halogen bulbs are 55/60 watts. Your stock bulb was 40/50 watts. So if your new bulb is an H4 then it will draw more power than stock. Make sure all the connections in the headlight circuit are clean and tight, the switches too.
On the chain 3/4 inch freeplay is right. Thats with you setting on the bike. A loose chain can add to the high speed vibration.
The gassy smell in the oil is leaky float valves and petcocks. Both need cleaning.
On the pods the short oval tapered K&N's don't work as well as the longer straight ones. I like Uni Filters. Get the ones that have the same size inlet as the carebs have
If your carb bells are 52 mm get 52 mm inlet pods.
On the forks they should have a drian screw to get the oil out then just pour more in the top. Some you actually have to take them off, remove the top cap and pour the oil out. Your Repair manual will tell you how to do it.
Leo
 
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Thanks for all of the info Leo!

My stock headlight was smaller than a normal 7 inch. I picked up a new bulb (I believe it is 40/60) and plan on re-wiring. The headlamp bucket only had one small hole to route the wires through so I had to do some modifications. Ill post some pictures soon.

Brake pads came in today and I am working on the install. the front caliper will only collapse so far, (with the cap off of the master cylinder) there may be a ring of gunk built up inside the caliper piston that isnt letting it seat all the way with the new pads. Only tore down the front so far.

I changed the Oil, but I suspect that I will have to fix this problem soon with the float valves/petcock.

I can see this turning into a build thread ha ha.

Just to be sure, what setting should the petcock be on when the bike is parked? (yeah I'm new to bikes:shrug:)
 
Just finished up replacing the pads, and finished with the new headlight bucket install.

Looks like I'm going to have to replace the front caliper piston too, the one currently on the bike is pretty gnarly.

Here are a few pics...
 

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Here's my take on the caliper piston. Take it out and get all the schmutz off of it. If that is all rust and pitting, yep, replace it. If it's grime and rust stains, try polishing it with 600-800 grit wet sandpaper. If there are a couple of small pits, it's still good, if there is more than that, replace. I wouldn't worry about the surface of the piston that does not ride in the bore- just the part that contacts the bore. A couple of pits can be filled with hi-strength metal epoxy and sanded smooth......or you can just replace them, but I'm cheap.
 
They were pitted pretty bad. I agree Chris! I am just going to replace the piston and rebuild the calipers.

The bike has been running strong since the oil change....a lot less vibration.

Still on the to-do list....

-front fork oil
-need to examine intake system more closely for leaks
-clean the carbs, check float level, sync..etc.
-check valve clearance
-check timing
-Clean chain and re-lube
-Check/re-lube wheel bearings

Eventual plans...

-Pod intakes
-shorty style exhausts
-rejet carbs
-replace turn indicators with something a little more streamlined

When the snow flies...

tear her down and rebuild her....cleaning and painting along the way.

Am I missing anything important that should be checked on a 33yo bike?
 
Question for you Hough....I just ordered some european style bars....did you have to do any modifications to your throttle cable, or any other cables for that matter?
 
J-B Weld should work, but this is only for small pits. I did not modify my cables in any way when I replaced the bars.
 
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