Just got 81 XS400

[Lepttack]

Hey all, I'm new here, and new to the motorcycle game. Well not fully, I'm more of a moped guy, mostly vintage Puch. Most all my bikes have been modified almost all the way around...kits/carbs/pipes/frames/bars/suspension/wiring/cables, just about anything on the bike. So, I trade a '77 Puch Newport for my friends non-running '81 XS400. This is my first motorcycle, but I have a solid base of knowledge in small 2stroke tuning and 2 wheel mechanics so I'm really excited to get into this thing as a 4stroke project. When I got it the carbs were pulled but not taken apart and the battery was stored inside. About a half tank of gas in the tank, no rust, kicks over just fine. Needs a new throttle cable for sure, could use some spark plug wires (weathered), probably needs a new battery.

I plan on doing an oil change, new battery, new gas lines, flush the tank, new plug and then just try to fire it up and see how it runs. Soon after that...bars, tank and covers painted and I don't know, we'll see how it goes from there.

The manual I got with the bike is for the 650 of the same year, am I going to be fine flowing it for the most part or are things really specific? I know I can see manuals here, but having paper is so nice. I've been looking over the forum and I see there is lots of info out there about getting started, but if you have some tips let me know.

Oh also, can somebody help me find a place where I can double check the model with the VIN? I was told it was a 81 XS400 Special, but I don't see much of the special stuff on it...thanks

 

[OliverB]

Welcome to XS400 ownership and the forum! Don't have specific knowledge about the manual differences but I do know the engines are different. You could download a PDF file and print out the manual - I did.

I still have my Dad's 1977 Batavus moped with less than 1K miles on it. It's in great shape and still runs fine.

New ignition wire pieces can be bought from mikesxs.com. They specialize in 650s but the wire pieces they send are the same type as the O.E. Get new NGK plug caps if yours have not been recently replaced. Spec is 10K ohm but the ones available today are 5K ohm and work fine. Use NGK non-resistor plugs - easily ordered from Advance Auto.

Go over the carbs carefully to check for internal shellac and plugged passages. One problem area on our carbs is the very small o-ring at the bottom of the idle mix screw found on the top of each carb. The o-ring becomes dried out and cracked and leaks air causing all sorts of improper idle problems. If yours have never been tampered with from new, there may still be a plug over the screw. You can carefully drill out the plug to access the screw. New idle mix screws and o-rings can also be ordered from mikesxs. When reinstalling the idle mix screws, set to 3-3.5 turns out. Factory EPA spec setting was 1.5 turns out and that is too lean. You might also order a set of choke rod gaskets and butterfly shaft gaskets if yours looked aged and cracked.

 

[HoughMade]

Were I you, I'd print out an XS400 manual and use that. PM me if you want to know where to get an e-mail of a manual in pdf. There are enough differences between the XS650 and XS400 that it will get frustrating.

 

[drewpy]

welcome to the forum

I got meself an Italian import Gilera touring circa '72 its in bits ATM awaiting resto

 

[Lepttack]

So I got 'er fired up last night! New plugs, battery, gas and she runs! Couldn't help myself, so I took it for a spin around the block. Everything works...lights, brakes, shifts just fine. Here's a few things I've noticed this far:
- it idles low, around .8-1 grand rpm, should be an easy adjustment
- the left carb seems to leak just a but from the, I think, butterfly valve gasket and/or bowl gasket and/or the vent thing on the bottom of the bowl.
- there is a hose about 1' or so long coming from the top of the right carb boot/coupler that leads to nothing. As the bike revs it sneezes (my best discription) occasionally right around 2-3 grand rpm
- the left muffler was rattling a little bit, it was coming from the inside. To me it sounded like a loose chain on a chainsaw kind of a rattle. But I traced it back to the exhaust for sure, not the case or anything.

 

[ahale2772]

that hose coming from the right intake runner is the vaccume hose for the petcock, if its not hooked up and is open to atmosphere it will run like crap...coule be your idle issue

 

[bcware]

Haha, yes, a loose petcock vacuum line is a vacuum leak. The fuel petcock shouldn't work on 'run' with it off, only 'prime.' The vacuum leak would definitely be the cause of the problems that were described. There is also a sprocket-shaped (on my '78) screw adjustment for the idle on the carbs if you need it. If it will idle at very low rpms let it; only increase it if you have to. Idling at low rpms is a good sign!

 

[OliverB]

Spec for idle is 1200 rpms but a good lower idle speed is acceptable, as bc said. Idle speed is often a matter of owner preference. Look under your carbs and you will see a knob that you turn slightly to change idle speed. No tool needed, just fingers.

Rattle in a muffler is not unusual for a machine this old. Got a rattle in one side on mine. No big deal as long as it doesn't bother you too much. Mine is mostly at cold idle.

 

[Lepttack]

Turns out the leaky carb was just loose bowl screws...like really loose, I got the vaccume line hooked up and found the idle adjustment. So far really easy. Now that the easy stuff is out of the way and I'm learning my way around this thing, I'm on to the stuff I need to do before I really hit the road. Tank needs to be repainted, oil still needs to be changed, and the throttle cable really needs to be replaced. Ordered a throttle cable from mikesxs, probably do an oil change tonight or over the weekend and I'm thinking of paint ideas for the tank and side covers. Maybe strip the paint, some sanding and just clear coat the bare metal? Maybe paint a stripe down the middle of the tank? Bondo over the badge mounts and just paint the entire thing? Just throwing stuff out there. Black side covers for sure tho.

 

[bcware]

I saw some clear coat at home depot not long ago specifically designed for bare metal. Normal clear probably wouldn't hold up well.

The easy stuff is out of the way? Changing a cable, removing/painting a tank and side-covers, and changing oil are also extremely easy

 

[OliverB]

Diesel grade oil 15w40, any name brand, is excellent for your engine!

 

[Lepttack]

Yeah reading over that again, I know all that stuff is easy...I think I meant the stuff that I was worried about is out of the way. Starting out with a non running bike that I'm unfamiliar with is one of this things that could go really good or really bad. I'm glad it went to the good side of things. Also just ordered bars, black "super bike" bars (3" rise, 3" pull back, 29" wide), should be sweet.