1981 Yamaha XS400 Special Problems

I’m new here, and would love anyones input on my issues.

I bought an 81 XS400 Special off of craigslist a few weeks ago and been having a ball with it so far. Unfortunatly I’m rather short (5’3) and cannot flatfoot the bike.
I wanted to know if anyone could give me ideas for lowering the bike anywhere from 1 inch to 2 and 1/2 inches? The shocks are already set at the lowest setting (the stock ones I believe)

Also, I’ve noticed some issues I’ve had, and I’m just learning about mechanics so I don’t know fully how to address them on my own without just taking it to a shop. But I really want to learn as I plan to keep this bike for quite a while. Here’s what I’ve noticed… :

If I get under 1/3 of a tank of gas (with plenty of fuel in the tank) I tend to have alot of stalling issues while idling. I’ll pull up to a light or stop and it’ll stutter a few times and die, and when I pull over, I still have plenty of gas in the tank.

Also, The service manual I own for the bike says it is supposed to idle are 1200 RPM, but I cannot get the bike to start consistantly or idle consistantly without stalling or slightly hunting RPMs. Like I will set it to 1200 properly, and it will hunt between 950 and 1300 RPMs at random times. Right now it’s sitting around 1450 or 1500 only to keep the idle consistent.

Thirdly, I was made aware of and oil leak before I bought the bike, and it seems to be getting a bit worse. Right above where the side stand goes down, there is the slightest oil leak…and before I go taking things apart I thought I’d ask for some direction. I did take off the sprocket cover to try and specifically isolate where the leak was, and even after cleaning out the whole thing with a toothbrush and cotton swab, I still couldn’t find anything definitive.  I am currently using 10w-40, which is consistent with the previous owner.

Next., electrical issues…The headlight is rather weak, I don’t know if that is electrical or just the light itself. It’s only useful while the highbeams are on, and that’s only to light up roadsigns. The high beam indicator doesn’t come on while the high beams are on. And my Speedometer backlight won’t come on, while my tach’s will. That could be a burned out lightbulb, though. Makes night riding very difficult. lol

And lastly, the other day I went to the mall and parked her in neutral on flat ground. After going about my business and coming back to the bike and attempted to start her. The light panel said she was in neutral, yet when I hit the electric starter, she jumped forward, as if in gear. It happened about 3 times before I Just pill the clutch cable in.

Thank you guys alot for anything you can come up with. I know alot of these problems can easily be fixed with a decent amount of money, but I barely could afford to purchase this, so I’m trying to go as DIY as possible.

Also, if anyone has a REAL service manual for this, It would be helpful. If not, I can scan my book, since I think I saw others asking for one.

I can try to post some pictures as well if you all are interested.

Congrats on the purchase. XS400’s are great bikes.

1 – Lowering. Easiest way to drop the bike slightly is to lower the forks in the triple trees. I would start by dropping the forks about 1/2″, then move to 1″ if its necessary. However, to keep the steering geometry as close the stock as possible, lowering the bike bike shaving foam out of the seat is a great choice.

2 – When you are sputtering at 1/3 of a tank, are you switching your tank to reserve? Your tank has a reserve to help prevent you from becoming stranded. As the bike sputters and runs out of gas you move the petcock to the reserve position and can happily cruise another 30 or so miles before you’re bone dry.

3 – You’ll really need to isolate the source of the leak before I can help too much. It’s likely either coming from the countershaft (front sprocket), or the shifter shaft. But there are other sources. If it’s just a few drips here and there, I wouldn’t even bother. If it gets real bad (pooling oil everywhere you go) then I’d consider fixing it. It’s an old bike – old bikes leak sometimes, it’s part of the charm.

4 – The headlights on many bikes of that era are weak. Make sure the light itself is pointed down towards the road. Sometimes a few degrees adjustment can make a huge difference. You can also buy a new 55w bulb down at the auto store for $3 and see if that brightens things up.

5 – The neutral issue could be many things. Just verify its in neutral by pushing it back and forth before hitting the starter and you should be all set.

Oh – and your idle isn’t quite smooth because the carbs are slightly out of synchronization and need some adjustment.

Evan Fell

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