The XS400 'flaws'

[willem]

Yes, the XS400 has them, like any bike, and I'd like to address the different 'weak spots' here for future generations. Knowledge is power, right?

1. Obviously, the carbs. They are the no. 1 cause of issues on these bikes, and clog up more easily than almost any other motorcycle's carbs.

2. The swingarm bearing. I've seen/read/heard about many of them failing. They are also often overlooked in the maintenance, but they are a weak spot.

3. The ignition module on the DOHC bikes. It causes electrical issues (i.e. loss of spark, bad ignition timing) for no apparent reason.

4. The fuel tank on DOHC models, and mainly the placement of the petcock. Even in reserve, it doesn't drain from the bottom of the fuel tank, leaving any water in the bottom of your tank to accumulate over time, causing rusting of the tank.

5. The fuse box. The connections get corroded easily over the years, causing all kinds of electric malfunctions.

6. The center stand; it rusts, breaks and bends.

7. The seat pan on SOHC bikes.

8. Voltage rectifier/regulator.

anyone else have good ones?

 

[Scorpio1963]

Hard to find nuetral and shift into 5th gear.Not to mention theres no spread between 4-6th gear.RPMs rap out quickly between those gears.

 

[Lupe]

from the standpoint of an OHC owner:

- fuse box
- center stand
- seat pan (not the Special models)
they are all a bit weak.

The wires from the generator. It is almost impossible to get them oiltight. Bad idea to use textil coated wires there.

 

[Specdog]

Voltage regulator/rectifiers are also common problems. Just about any 30+ year old bike has these issues, but I believe Suzuki and Yamaha have more failures. Honda used a better quality Schindengen R/R.

 

[xschris]

Your right! Any bike 30+years old will have flaws

 

[Scorpio1963]

Its called wear and tear aint it Chris?

 

[willem]

Updated

And to explain a little bit: with 'flaws' or weak spots I meant the parts on the xs400 that tend to last a lot shorter than they do on similar bikes of that age.

@aaron: Although very true, the gearing isn't great, it's not really a weak spot. It's not broken, it's just not designed the best way I guess.

 

[Scorpio1963]

Correct these gear boxes are design with crappy gearing.A geuine flaw not caused by old age.

 

[Lou Ranger]

So, to summarize, basically, the entire bike is designed with and constructed out of hundreds of flawed, weak parts
And yet, we do love them so! ..

 

[willem]

it's the imperfections that make the bike perfect!

 

[16VGTIDave]

With respect to gearing - The higher the road speed (or air speed if dealing with a head wind), the closer the gear ratios will have to be to keep the engine in it's power band. This applies to all vehicles. Aerodynamic drag increases exponentially with speed, and the aerodynamic profile of our bikes is terrible. The Seca had the "best" aerodynamics of the XS400's, and it is a moving brick compared to a modern sport bike.

If you want to rev your engine lower (a common complaint around here) and still maintain a certain speed, you will need to increase the torque output of your engine at the lower RPM's. And the only way to do this is to increase displacement. Since we are limited to 400cc's, the only reasonable option is to rev the engine. If this isn't to your liking, your ONLY option is to buy a different bike or transplant a larger engine into your bike.

Complaining that your bike is revving too high is not going to change the physics involved. The engineers at Yamaha put a lot of effort into designing our bikes and considered many factors before deciding (compromising) on the final product. Either learn to enjoy the sound of your engine revving at 6000+ RPM or resign yourself to buying a big displacement bike.

I personally LOVE the sound of my engine at 9000+ RPM.

 

[xschris]

I like the 6 speed trans in both my 400's I can always find the right gear for any road conditions.

 

[Lupe]

@ Dave: great explaination

As far as I can judge, the gas tank is only a problem on the Seca. Maybe the Maxim too. I do not know, we only have one here in Germany

I never heard of issues with the older models. Of course they corrode too, but not in regular use.

PS: I like the right side of the tacho!

 

[drewpy]

I have ridden my FZ600 and tbh its more "revvy" than the xs as its has 4 pisitons at it instead of two. granted its got more power but I do prefer the twin.

I rode the FZ with a mate on his dohc xs400 and it kept up with me till 80, what more do you want?

 

[Scorpio1963]

I personally LOVE the sound of my engine at 9000+ RPM

What was your speed with those rpms just curious.

 

[16VGTIDave]

In which gear? I have no problem hitting 9k in 1st thru 4th. Often 9500. 5th gear I haven't pushed that high, yet. I might admit to getting up to 135kph (80mph) once or twice...

 

[arfstrom]

Often 9500. 5th gear I haven't pushed that high, yet...

Yea, Me too. I would love to see if this bike could hit the theoretical Max 105MPH, but once it hits about 80 to 85, I start to think there is a cop on the other side of each car, or bush. Note:with the T17 front sprocket, I am doing about 7300Rpms, for about 80 MPH.

 

[Scorpio1963]

So Dave you say that you often rpm your bike at redline?I have yet to rev my bike over 7500rpm and go over 75mph.So I have hardly pushed it to it limits.Anything faster and my mufflers start vibrating.Once I get the new mufflers secured down since the bike is so much quieter I`ll step out of my comfort zone a little more and see if I can hit 80mph

 

[16VGTIDave]

DOHC redline is 10,000. And to answer your question, yes, I often push 9500+. When riding with enthusiasm, I shift when I feel the acceleration falling off, which is around 9500 for my bike. How else can one ride with the big boys and keep up? Shifting at 4 or 5k is what the HD guys do, just like their mommy's would tell them to do. 7500 is where our engines come alive.

I twist hard and let her sing when I want to move. And it is a sweet song that she sings! Just like the kid on the Ninja 300 that I passed this evening on the way home found out. We had both stopped at the same corner and turned the same direction. He was busy going slow and shifting frantically when I got fed up and passed him in 3rd gear. I think he was in 5th and probably ready for 6th. By the time I hit 4th, he was a speck in my mirrors, and I would have lost my license and had my bike impounded if I had been caught on radar by a cop...

 

[willem]

Exactly what I do, I shift when I feel the acceleration fall off. Pretty high revs and lots of noise coming from my holy exhaust

And I can confirm the Seca does 85 on a flat road with sidewind. Went to check how fast it is a while back on a road here where 80 is allowed. I can probably squeeze some more out of it after I've fixed that exhaust and I do a re-sync and mixture adjustment, but I'm not sure I need to. 85 is plenty on this thing lol