First XS400

[hjennings]

Greetings all!

I've built custom cars and Harleys but never messed with metric bikes before. I recently inherited a couple bikes, one of which is a 1978 XS400. Well I think, anyway.

It has the older 9 digit VIN. I went to my nearest Yamaha dealer today and showed a guy there the picture of the VIN stamp. He asked for a picture of the bike and immediately said it looked to be a '78 or '79 XS400. VIN starts with 14V-002 if that helps.

Engine spins easily. It appears to be all complete except that it is missing the carbs. I have found some on eBay. I guess that's the first step. Anything to look for here?

I've rebuilt automotive engines before so if I strip this one down and start from the ground up, I would be all for a ring, bearing, and gasket set. I've found gasket sets, but nothing for rings and bearings. Any sources?

Once running I'd like to replace the 16"/19" spoke wheels and drum brakes with 17"/19" period correct mags and disc brakes. I'd need the mag wheels, front and rear rotor and calipers, front and rear master cylinders, lines, and correct front tube fork(s) to mount the caliper(s) (depending on single or dual rotors).

My uncle was an old car/motorcycle guy and he was in the middle of several projects when he passed. So finishing this project be a nice tribute to him. It will be sort of a bobber look when done.

I do professional bodywork and mechanical work, but have never touched a metric bike before, not to mention one this old. Autos, yeah, just not bikes such as this. So I just want to make sure I'm not doing anything stupid before it's too late. Any input or advice is appreciated.

Thanks!

 

[DARKMIDKNIGHTWARRIOR]

Welcome to the forum! I'm new to old bikes as well so no help from me sorry.

 

[xschris]

Welcome to the forum. That vin# is for a 1982 sohc xs400. Standard rings can be found on ebay but as for bearings they are very hard to come by. I would start by getting a manual or download the PDF from this site and start reading

 

[bcware]

I'm not trying to talk you out of a complete tear-down as it sounds like you won't have any problem completing the job. I will simply voice an opinion from the value perspective, bang for the buck, etc.

The motor is so easy to pull out that I'd honestly just start with gaskets/seals and a top end rebuild and inspection. In my experience almost all failures in a 70's era UJM parallel twin are going to occur in the top end, usually due to oil starvation.

To get an idea of the weak points in this particular motor search ebay for top ends/heads (complete ones with a cam); you'll find few and they will be relatively expensive.

Now search for bottom ends/crankcases; there will be tons of them and for relatively cheap.

This tells you where the motors are failing; everyone needs top ends because they are what is going bad (from the pistons and up to the cam). Few people need bottom ends and they are difficult to sell.

Now, about the brakes. Are you swapping the wheels and brakes over for looks or for performance? I have a '78 with drums and wire wheels front and rear and I am a very aggressive rider. There are no issues with lack of braking power. I can stop on a dime with them. The only downside to drums is brake fade when they are used aggressively over and over again as in racing. Very wet conditions might also pose a problem. A wire wheel and drum brake setup will also be very light. In general there is much more demand for wire wheels and drum brakes. Much less people want to swap to mags. It's usually the opposite. The best part is no brake fluid to mess around with.

If you still want to do the swap don't get screwed. You should be able to find someone willing to do a swap. Maybe you could even get them to cover the shipping too

 

[Specdog]

Yeah you have an '82, you can also tell by the all black paint treatment, buckhorn bars. Your's is the econo version. The same year also came with mag wheels & front disc. The carbs for the 82 are a bit different than the earlier ones. The bodies are the same but the mains are leaner, no needle clip adjustment, plastic floats with different heights.

 

[hjennings]

Thanks everyone for the help! So looks like I have an '82. Thanks!

Bcware, thanks for the info. I have found several gasket sets so I'll probably just go that route then. My thinking was that if I was going to tear it down that far I'd just replace the rings and bearings. But if I can't find 'em, then I can't find 'em. Lol. So on the upper end rebuild... As I said before, I'm new to these engines. With a car I'd expect to redo the valves, true up the head, and valve seals. Is that the same here, more or less? I haven't found anything as far as valve seals for this engine (unless that would come with the gasket set). You mentioned cams going back (worn lobe or whatnot, I presume). If that's the case, am I stuck with buying a used one or are there replacements out there?

On to the brakes... I'm sure drums would be adequate, but I really like the looks of the mags for the type of brat/bobber look I'm going to go with on this bike. My spoke/drum wheels are a bit weathered. So my plan was to buy everything I need for the swap then clean up the stock wheels and sell them. I do powder coating, so thought about throwing some powder coat on them, or just polishing them up and selling them. IDK yet.

Xchris, I've been looking for rings on eBay but no luck yet. I'll keep looking just in case I need them.

Specdog, I am a bit ashamed to admit, but I am a long ways away from a carb expert. I've rebuilt complete engines, but I've rarely messed with a carb, and never a small engine carb. So anything you can tell me about these is appreciated. So when looking for replacements I need to look specifically for '82 carbs?

I've been searching eBay endlessly. Almost all I'm finding are trash carbs missing parts. :/ Any ideas for better sources?

Thanks all!

 

[levdir]

PartsNMore doesn't have a way to link directly to a part, but valve stem seals are at the top of this list http://www.partsnmore.com/parts/yamaha/xs400/?filters[category]=engine. Dime City Cycles has complete carbs but they aren't cheap. You're looking for Mikuni BS34 carbs, if that helps.

 

[hjennings]

Levdir, THANKS!!

You guys have been a ton of help. Already love this forum. I'm going to start tear down of this bike probably next week. Then the hard part... deciding on a paint/color scheme.

 

[hjennings]

Oh and just to show off, here is the most recent custom paint job I did. This is one of the half-tanks for a 1976 Harley. Friend of mine crashed it. This tank was completely crushed! Under normal circumstances it would have been cheaper to just buy a new tank. I did it as practice, just to see if I could get it straight. Then went crazy with the paint. Let me know what you think. PS probably want to turn the volume down. Shop was loud that day.

 

[xschris]

Very cool paint

 

[levdir]

Oh, that's damned cool. Does it get a kind of gradient from orange to black as the engine heats up?

Re: paint, this is an idea I had for my bike. I'm a fair ways off from that kind of finishing work, but it's fun to daydream. Thinking flat orange, flake green.

 

[hjennings]

There is a thermo paint on top that is black. It remains black at 84 and below degrees. Once it hits 85 degrees it turns clear, revealing the paint below (which in this case is orange with black lettering).

I have another tank I'm doing now. It is black and I'm adding "realistic" flames. I'm going to go over it with the same black thermo paint. The *idea* is that on a nice day that is 84 degrees or below, that the heat from the air cooled big V-twin will heat up the tank enough to make the flames appear. As you ride the air will cool it, causing a flicker effect.

At least that's the idea. This one is on a tank I picked up and not for a customer. Going to throw it on a friend's bike when it's done to run it and test it out to see how it turns out.

My gf suggested a burnt orange / black combo. I'm a dork when it comes to paint, but I believe each vehicle has a "soul." I don't like putting a Chevy engine in a Ford vehicle. I don't like putting Honda color on a Yamaha... if that makes sense. When I see orange on bikes I automatically think of Harley orange. I like to keep colors factory colors or something completely custom you wouldn't mistake or another make.

My daily rider ('05 HD Dyna) is candy red over black, gloss black, and chrome. I'm also painting an old school Kawasaki candy red over gold with gold leaf lettering and gold leaf stripes on the fenders. I like trying new things and experimenting. Like on my personal bike, I'm going to redo it. It just looks black, except in certain light where you can see a red glow. I wanted it more red (to contrast with the black engine pieces and black mag wheels). I wish I could draw like Chip Fouse or something!! But since I can't, I just have to imagine it and spray the paint to see how it turns out.

I'm just brainstorming.... Thought of a flat grey/something combo, silver/black combo, a darker blue/white combo, or maybe even a black/white combo. IDK just throw things at the wall and seeing what sticks.

 

[hjennings]

Welcome to the forum. That vin# is for a 1982 sohc xs400. :

I found another site that said -001xxx was '80 and -101xxx was '81. That led me to think that -201xxx would be '82. Although -000xxx, -001xxx, -002xxx would make a heck of a lot more sense. So it's that 6th digit in the 9-digit VIN (or do we call that a "serial number"?) that shows the year?

 

[levdir]

The thread called "The Mule" has a cool looking gloss black-on-flat black paint job. I really dig it. Check it out, maybe, there's good photos.

 

[Specdog]

Specdog, I am a bit ashamed to admit, but I am a long ways away from a carb expert. I've rebuilt complete engines, but I've rarely messed with a carb, and never a small engine carb. So anything you can tell me about these is appreciated. So when looking for replacements I need to look specifically for '82 carbs?

I've been searching eBay endlessly. Almost all I'm finding are trash carbs missing parts. :/ Any ideas for better sources?

Thanks all!

You can go with any year XS400 SOHC carbs for your '82. In 1982 the EPA was going crazy, and most carbs from that era are set up very lean to comply with regulations. The earlier carbs will work fine. Check the classifieds on this site, I've seen complete carb sets available in the past. There is an online manual available on this forum. You can see the different carb specifications for the various years.

 

[xschris]

I found another site that said -001xxx was '80 and -101xxx was '81. That led me to think that -201xxx would be '82. Although -000xxx, -001xxx, -002xxx would make a heck of a lot more sense. So it's that 6th digit in the 9-digit VIN (or do we call that a "serial number"?) that shows the year?

You go by the first three letters to find the year. The 78E and 79F where both 2Lo so you had to go by the numbers and how they started to now the year, but if you look at the build date that will tell also ( 6/77 is a 78 model and 6/78 is a 79). Your bike is a 14V so it's a 82. My guess your build date is 7/81 or there about.

 

[hjennings]

Thanks again! Digging this forum!

I'll check out "The Mule." Sounds like an aggressive looking bike. That's what I want to go for. I'm really leaning towards a 60/40 dual purpose tire. I don't want it to look like an enduro, but rather a street bike with attitude.

 

[Lana]

Hi,

my xs 400 is an 82, but I haven't been able to find any info on model cause my serial number isn't shown anywhere, it starts with 15G, someone posted something somewhere about different vins and what they mean, but it wasn't listed there either, and now I can't even find that post here. plz help.