New 83 Maxim owner from Toronto Canada, need some help


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Milton, Ontario, Canada
Hi All,

Hope y'all having a great day.:D

I bought a 83 XS400 Maxim over the winter. It was stored at the sellers place for a month, then I moved it to a buddy's, and it was there for a month also. I rode the bike and practiced when I moved it to my buddy's, it was running a bit sluggish; power comes on laggy and abruptly. The seller said the carb probably needs cleaning when he sold it to me.
I rode it about 3 weeks ago to top up the gas tank in order to prevent rusting. The bike complained a lot initially, jerking when I put it into gear. But it eventually rode fine.

Spring comes around, and I get a short break off from work. I go to my buddy's all excited about shooting an intro vid for this forum and do some riding:bike:. Bike started off sound:thumbsup:, then quickly died:mad:. Pulling choke, petcock to pri, and giving it throttle did not help. Battery got drained and hooking it up to the car produced the same cranking, but not turning over:eek:.
I initially thought it was a clogged carb, since it has been ridding sluggish and the owner said car needs to be cleaned.
But buddy contacts me a day later yesterday saying his whole house smells like gas and it was coming from the bike. I thought I had left the petcock on Prime, or had forgotten to place the clip back on the fuel like. I thought I had flooded the cylinders:doh:.
I went over today and checked it out. The petcock is only at ON position, and the fuel line was not leaking. The head gasket however did look wet, and gas could have been leaking from there. I got the spark plugs out and turned the crank with a wrench, no gas came out. I also siphoned as much as out of the tank as possible, couldn't get all cus the damn hose kept on curving and not reaching the bottom...:banghead: the gas looked clear enough.

So my question is:confused:. What could have made the bike die after initially starting up?
Is it carb related? Does potential flooding exclude that?
Could it be related to the head gasket? If so how to fix it?
Is there an off position for the petcock so I can take the tank off?
How to prevent damage when taking off the fuel line from the petcock and the carb? That thing look s pretty old and fragile...Where to find replacement parts?

Here is the youtube vid I shot. Sorry for the wind noise, and my rambling. I don't have a vid of the engine just cranking, but it pretty much sounds like the last crank of the first video.

My plan right now is to bring multimeter with me and check spark and battery charge.
Any tips and suggestions!?? Thank you all :)


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Welcome! Congratz on the new bike.

Yes, this sounds a lot like a carb issue. And since that's the number 1 cause of problems on these bikes, I would suggest you take the carbs off and apart straight away. The head gasket is not really in contact with the fuel or the carbs, whatever is leaking there is coming from the engine oil. These two are unrelated. Nevertheless, keep an eye on your oil levels and you could consider changing your head gasket.

My bike also ran OK when I bought it, it wouldn't start well, it would stall sometimes, basically be 100% unreliable until it just decided to quit altogether. After I cleaned the carbs, cleaned them again, and again, it ran perfectly.

Your flooding is also a carb issue, the float might be stuck which causes it to spill gas into your cylinders and towards your air filter. So just take those carbs off, clean everything and probe through ALL the small passages. Take your time and make sure you probe it with very fine wire and don't miss anything. It's better to do it right the first time than to take 3 times like I did. Have a little look around the forum for how-to and tips. Boiling the carbs works (in combination with probing the passages!), either in vinegar or lemon juice or something, and if you can afford it, ultrasonic cleaning is probably best. But I also managed without boiling or ultrasonic.

And get an inline fuel filter (read about it here )
it helps enormously with preventing trouble in the future, and it's cheap!

New fuel line is probably also good to install if your old one looks crappy. You can just go to an autoparts store or something and ask for it, they usually have it. Just make sure it's the right diameter and its a fuel line. The black rubber kind is best, the clear stuff gets hard after a while. The inline fuel filter is also available in most autoparts stores.

There is no OFF position on our petcocks. The ON and RES positions shut off the fuel supply when the engine is not turning, so that's as good as an OFF (given your petcock is working correctly of course). If you're taking off the tank just put it on ON or RES. These operate on the vacuum, there is a separate vacuum line from the petcock to the carb boot which allows the vacuum generated in the cylinder to engage the fuel flow in the petcock. You can just pull this line out of the carb boot when taking the tank off as well.
Hi Willem. Thanks for the reply :)

My bike also ran OK when I bought it, it wouldn't start well, it would stall sometimes, basically be 100% unreliable until it just decided to quit altogether. After I cleaned the carbs, cleaned them again, and again, it ran perfectly.
I was planning on taking it out and cleaning it. I already bought carb cleaners and I plan to get one of those outdoor camping stoves and boil the carbs. Some issues I am unsure about are:
-I only have the most basic tools like 11-18mm sockets, screw drivers, and magnet stick. Are there any special ones needed?
-What about the settings, such as # of turns on the screws in the carb? Which screws can I take off and which I can't? Where do I find such info, preferably online. Since I am using up precious vacation days.
-Is bench synching the carbs good enough?
-How do I set air/fuel mixture adjuster? It's important, no?!
-How exactly to align upon reassembly?
this post makes it seem pretty critical, but didn't exactly outline how to do it.

I already bought in-line filters, and was planning on putting them on. I just didn't yank the fuel line off yet due to not having another one ready, and also not knowing how the petcock works with the line unplugged.

Lastly, and I think most importantly. Where do I find the service manuals, either in paper or PDF format, that is suitable for my bike. The vin # is JYA12R007DA104127. Other than it being XS400, I couldn't find any other information on it. The exact model # and etc.

No problem :)

Manuals can be found in the sticky post here in the garage part of the forum. I don't know how to determine your model from the vin #, but if you post a picture of the bike here I'm sure we'll ID it in no-time. Otherwise, try this:

If your engine says YICS on the side, has a 6-speed gearbox, has a square headlight, says SECA, Maxim or DOHC anywhere, you'll need the DOHC manual (later models, 82-84, might have little bit different style but mechanically the same as in the manual).
If not, use the SOHC manuals. You can also try looking around the forum at pictures of other people's bikes, they usually say what theirs is and odds are there's one like yours around.

I haven't needed any special tools just yet. Just make sure you have the right sized screwdrivers and plenty of sockets, and a tool with which you can take your spark plugs out. I use a pipe like this (what's that called in english??) for the plugs. You could consider getting a multimeter to figure out any electrical problems you might have, and possibly a soldering iron. You may run into a size 10 bolt here and there as well, so just get 1 more socket. I think the battery is attached with size 10's.

Also it's very wise to get a torque wrench, if you're going to do anything to bolts that go into the frame, engine or other irreplaceable parts. If you ruin the thread on something like that, you're not going to forgive yourself. I actually don't have one yet, but I am going to buy one soon. Make sure if you buy one that it's the right range, which is the lower end of the spectrum (so low torques)

Try not messing around too much with your settings at first. Cleaning the carbs should be a major improvement, and possibly the only one needed for now. Bench synching is not really accurate, but will get your bike running. Try not messing around with the synch screw first, and if it runs horribly you can try adjusting that.

Mixture screw should be 1 1/2 turns out, but that's not an exact science. Try leaving it the way it is first, and adjust after cleaning and running.

Don't separate your carbs when you're cleaning them. You don't have to, in order to get them clean, so why bother. Your manual should give you a little bit of info on what you can take off and leave on. But basically, you can take off your vacuum chamber cover, float bowls, floats, needle jet, main jet, float needle, vacuum membranes and drain screws in your float bowls. Pretty much everything, except the sync screw and mixture screws. Have a look at the videos from bcware in here:

Syncing carbs is a 'fine tuning' effort, so to get your bike running perfectly, after getting it running OK. Focus on getting it going first, and then you can try this:

Is that a spark plug too in the picture!!?? I have one in the glove box, and had no clue what it is :D. GREAT!

So I cleaned the carbs. The bike now runs. I didn't find any yets/emulsion tube, and probably ran into the problem as the post below. I removed the small jet and washer, and had flipped the carb body many times with both covers off, nothing came out. I will try to remove it to clean in the future. Any tips on removal would be appreciated

I also couldn't put the carbs back on correctly. I believe you saw my post in the other thread. Thanks for your inputs. I will try it the next chance I get. Right now, one boot is completely off, and other is covering 3/4 with the other 1/4 folded in on itself.

I didn't have a stove with me when I cleaned the carbs. Once I know how to remove and install the carbs more easily, and figure out how to remove the emulsion tube, I will boil the carbs and get it done properly.

I will keep it updated here! :D Thanks.

By the way, how do you clean the air filter? I have a 400K manual, and it says just to blow compressed air at it. Is that really sufficient?
yes sometimes that works quite well. There is only air from outside going through the filter, so apart from some dry leaves, bugs and dust it should be pretty clean. No oil or soot or anything. But if it's still dirty, try some soapy water.
I just remembered something. One of the drain screw for the carbs is 90% striped. I bought liquid wrench today in hopes of loosening it. If that doesn't work, how do I get it out? What size is it so I can replace it?

And am I correct in saying the boiling of carbs is not safe for the gaskets. If that's the case, how do I remove them? I read you can dip them in carb cleaner, which would loosen them. But I thought carb cleaners are bad for the rubber gaskets? Comments? :)

just leave it there, you can pour out the fuel when you take off the carbs through the in/outlets.

just peel the gaskets off, or spray them with some WD40 if they're stuck