Recent issue with my 400. Where to start?

The idle on my bike has recently gotten pretty funky.

Cold start: It starts kinda hard. It'll occasionally stop cranking, like the starter is being stopped by something. Once started, it idles around 500-700 RPM and tries to die if I choke it.

Warm: Once it's warmed up a little, it idles around 1000-1400 RPM and if I turn it off, then start it again, it's fine. Very noticeable lag in throttle response.

Hot: Once it's hot, idle goes up into the 1800-2000RPM range. If I goose the throttle, there's still a little lag and then it goes down from what ever RPM I revved it to to about 2400RPM, then takes awhile to go from there back down to whatever it's decided to idle at.

Where do I start? :lol:

 

Sounds lean, check those plugs.

 

Your cold start issue sounds like a leaky float and petcock (I assume the 400 has a vacuum petcock?).

As it sits fuel floods up into the carb throat and runs into the cylinders - making it very rich. Get enough in there and it'll hydro lock and stop cranking.

Check your oil for gasoline smell. Check float level with a clear hose on the drain - watch for the level to continue rising, might take some time.

 

Pull the Plugs.
Take a pic of the Business Ends - close-up and in focus.
Let's see what you're dealing with.

How confident are you that the Carbs are all Cleaned and working perfectly?

 

+1 for Ricks carb cleaning process,
Between tthe carb cleaning guide and the clunk guide, mine have been working great

But as MiCarl said, check your oil for a gas smell....
(yes, the 400 has a vacuum petcock)

 

Might be this weekend before I get those pics up, but I'll put them in here when I do.

As far as the carbs being cleaned and working... The guy I bought the bike from claimed to be a motorcycle mechanic. He also claimed the bike had been sitting for 13-15 years with the carbs off and he cleaned them and sync'd them after buying the bike.

I have put just over 1800 miles on it since I bought it in May, which puts the odometer at aroudn 7900.

 

Due to the passage of time, alone, it would be wise to Inspect and Clean your Carbs.
Any trace of Fuel left in the Bowls would have evaporated and left behind a varnish that would deteriorate and clog-up the Jets.

The more than 20-Years that have passed has undoubtedly taken its toll on the Diaphragm Piston Bores.
You absolutely must clean and refinish those Bores to have that Twin-Carbed Bike run great.

Look at it this way.
You are only going to have to deal with two Carbs!
You should be able to do the job in half the time it takes us 4-Carbed Bikes to do it.

One of my fondest memories is sitting at the Kitchen table shaking-down a set of Carbs off my XS-650 Special.
Once I got those Carbs Cleaned I had a new outlook about doing all the maintenance work the bike needed.

Don't be apprehensive.
Your bike will love you for it!

 

Wouldn't you know it. I go out with the video camera to get a video to show you how it's acting and it behaves perfectly. Cold-start, no choke, caught on the first crank and idle settled in just under 1000.

 

*nods*

It heard you....

Or maybe something in the float bowl, moving, sometimes clogging up the enrichment tube and everything else.....

If you have a couple days of downtime coming at ya, get them off and thoroughly cleaned.... can be done in a matter of an hr or so, but give yourself time to go over everything, dremel polish the tube that holds the piston (HUGE difference in throttle response) Plan to pull mine over the winter to give them a going over and finally clean up the outside....

 

I went out for a short ride last night after it stopped raining. Found this this morning when I was getting ready to go to work. Looks like I've got other problems... What am I looking at here? The other side of the engine is fine.

 

If it's gas I would assume a stuck float or bad needle valve....

But I can't see why it would leak out like that with out a gasket issue...

 

Looks like oil to me, see the patch on the exhaust, looks like the puddle on the ground came from that spot. I could be wrong, just makin an observation.

Head gasket maybe?

Are the cooling fins on the cylinder always that colour?

 

It's oil and it smells like gas, so my first assumption was head gasket. The puddle on the ground came from that as well. The cooling fins on both cylinders were always gray/silver. Right side still is.

 

Looks like the Head Gasket is leaking a fair amount of oil on you.
That side has the Dowel Pin and O-ring Seal that feeds the Top-end under pressure.

It never hurts to experiment and re-torque the Head.
You got nothing to lose and it might (slim chance) stop the leak.

Otherwise, you're probably looking at replacing the Head Gasket.
And, in a case like that ... you should have the Heads Mating Surface "Straight-edge" checked across the front, middle, back and diagonally.

If there's some warp in it; you'll need to have a few thousandths shaved-off the Mating Surface to return it to perfectly flat.
Check the Book to see what the maximum amount of material that can be shaved-off is ... that's important!

 

The book.... That's funny.

I've been searching since I got the thing in May and can't find a book for the XS400 Maxim. I can find one for the regular XS400, but it's a different engine. DOHC on the Maxim vs. SOHC on the XS. I've learned the Seca 400 had the DOHC engine with a 6-speed, rather than the 5-speed I've got, but I'm having trouble finding anything specifically for my engine.

 

I've been using a manual for a 1982 seca 400, i also check the one i have for xs360-400, but it only covers older (model years C, D etc) bikes. I can't find one for 1983 maxim without buying it (i'm cheap)

 

Here's the video I took last night when it was still behaving. http://s114.photobucket.com/albums/n241 ... tartup.flv

 

Holy christ that thing idles low hahahh was it warm?

 

No. It would go up to about 1000 RPM once it warmed up.

 

Mine won't stay goin cold without a touch of choke to get her warm. I am still dialing her in tho

 

Where can you find it to buy? I haven't even had that much luck.

 

Ebay is your friend if you're patient. There may be some onlnine retailers that will have it as well, but expect to pay close to 100 bux for it.

 

Here you go, Big Guy ... Do the right thing and get the Factory Book.

Don't balk at the price.
This baby will PAY for itself several times over in a real short time.

http://www.yamahapubs.com/html/itemsear ... del=XS400K

 

Alright. I think I'm gonna give it a whirl. The only thing that really worries me is getting the cams back in in exactly the same orientation they were in when I took them out. Any tricks to this other than a sharpie?

Is this thing an interference engine? Namely, do I get only one shot to put them back in right?

 

Get the Book.
You follow the instructions to the letter.
The Piston Crowns have depressions where the Valves Open.
To keep Compression High.
If you mess-up and time it wrong ... you could crash a Valve.
But, you won't.
We won't let you.

The Crank and the Cams all have permanent Timing Marks.
When the Timing is done right you have a visual element that lines-up with permanent markings on the Engine.

Replacing a Head Gasket is a "Right of Passage" for a Do-it-yourselfer"
Don't sweat it.
We got your back.

It's all about being organized and having the Text to refer too, to guide you each step of the way.
So, order the Factory Book and look-over the Cylinder Head Removal and Replacement Section and begin to visualize yourself doing what it says to do in the Text.

We'll even do a couple of things not covered by the Text to make the Bike run better after you take care of business and we get to the matter of putting a Gasket on there that ain't ever going to leak again.

Crack your knuckles and get psyched!
One step at a time.
Step - 1.
Book.

 

I have a PDF of the service manual for an '82 Seca. Is that the same book as the one you put the link up to, Rick?

If so, I can run it through one of my printers at work and put it in a binder and save myself $80.00.

It's got instructions how to disassemble and reassemble the engine in it, complete with torque amounts for the bolts. I can take that $80.00 and go get a decent torque wrench.

I won't be able to do this until next weekend at the soonest anyway. I'll need to get the mechanic across the street a case of beer too.

 

Somebody with a 400 will have to chime-in.
I don't know.
I've never even seen a 400. Even over at the Dealership where I hang.

Look-up the Timing Marks part. You need to be able to identify Timing Marks and where they line-up at Top Dead Center for the One Hole.

That, plus the procedure for reinstalling the Cam Chain and laying the Chain back on the Cam Sprockets is the KEY information you need to have right.

 

I'm not an expert by any means, but i'd think it'd be better to get the proper manual, especially when it comes to timing and engine stuff. The maxim most likely will be different from the Seca engine wise. Some things will be the same or close to the same tho.

 

I have a paper Seca/Maxim manual ....
They are basically the same through and through... just a 6 speed tranny in the Seca... otherwise ther rest of the engine is the same.
Other than that it's mostly cosmetic

Different fork length, larger tank on seca, 6 gears, larger rear sprocket , different carb jetting and headlight is different. All the rest is the same
Just took a quick look, all the pics in the max/seca book are taken from the seca

So he should be good to go....

 

Except for the fact that he bought the wrong torque wrench. Doesn't go high enough. Gotta drag the damned thing back to Sears now.

 

Okay, this is starting to get weird...

Pushed it across the street to the neighbor that's been a mechanic for most of his adult life. He kept saying he didn't think it was the head gasket. It's the right area for head gasket, but the oil on the fins is dry. Nothing wet. We started it up and tried to make it leak. Let it get hot. Nothing. Ride it around the town a bit and then back. Nothing. Put my 220lb ass on there with him weighing in at 130 on the back and ride it around some more. Nothing. No new oil on the fins. We can't make it do it again, so we've decided to change the oil and filter, clean the stuff off the fins and watch it like a hawk to see if it does it again.

Anybody got any ideas that might explain this?

Oh yeah. Checked the Yamaha dealer down the street on a whim to see if they might have the gasket. They've got a brand new 2006 FZ6 in the showroom that I drooled all over... Never thought I'd say this, but for once I think it was a good thing my ex-wife left me with terrible credit...

 

When i started to seriously think about gettin a bike, that was the first model i was drooling over as well hahah. If i got a new bike now, it would be a V-Strom or Versys.

Oh if only i was rich hahah

 

Well, ... if somebody decorated your cooling fins with a little bit of oil to try and be funny and shake you up ... they did a good job.

So, if you rolled it into the Hangar and the Crew can't find any reason to Ground your Aircraft ... fly it!

Glad it worked-out for the best.

 

Any tricks to easily clean it off the cooling fins? Like what works best?

 

Gunk or STP Engine De-greaser if you need to really clean the Engine right down to the shine.
Use the bio-degradable one especially for aluminum.

Aside from that ...

I Clean my Engine with a highly concentrated solution of Dawn Dishwashing Detergent.
If you do the Dawn treatment ... keep the Block and Fins wet with the detergent until you rinse it off.

If you need to Scrub, a short bristled nylon brush is the way to go.

 

I don't get it, but okay...

I cleaned it all off and changed the oil and filter today. Re-tensioned and lubed the chain while I was at it and found bolts to put my chainguard on with.

Then I went out for a ride. Rode rather tamely for awhile, then checked it. No fresh oil on the fins. Rode spiritedly for another 15-20 minutes or so and checked it again. Still nothing. Flogged the shit out of it for about half an hour. Still clean as a whistle...

I'll keep an eye on it, but for the moment, it appears to have stopped.

 

Forgot to mention. I pulled the plugs and they look about like #7 on this page: http://www.dansmc.com/Spark_Plugs/Spark ... talog.html

I'll try to remember to take my camera home and get pics. I'm gonna throw new plugs in there since I don't know the story behind these ones, then take a look at them after a tank or two of gas.

 

Definitely doesn't need plugs. They look better in daylight.

 

You are looking a teenie-tiny bit Lean.
A Hair ... maybe 2!
Add a Degree ... maybe a degree and a half of Richness.
It should do a couple of things:
Settle down your Idle and make it really steady.
Give you some nice acceleration out-of-the-hole.

Give it a couple of rides after you tweak it and check the Plugs, again.

 

And will add a nice growl vs a whine
And if yours responds like mine, reduce some engine braking.....

 

I've got the manual for the seca 400 in a PDF format if you want me to send it to you....message me back

 

I've got the manual for the seca 400 in a PDF format if you want me to send it to you....message me back

 

I have that exact bike and sometimes have the same problem. A friend pointed out the I have rust in the gas tank. Sometimes when I start the bike but don't ride it, We believe some of the rust gets in the carbs, and then they fill up and drip on the floor. I am currently getting ready to seal the inside of my tank. I took the carbs out and noticed tiny rust particles in there causing me to believe that was the problem.

Just my two cents.

 

Add an inline fuel filter!!!

 

I did that. It didnt affect my problem. I had too much rust particles in the carbs already.