Noah Adams

Was running it with no air filter while testing (carb boots are a 30 minute ordeal to get on and off) and it was still having the issue. I took it to a local bike mechanic that I trust... he's going to give the bike a good look over while he's at it (good for a bike this age). I'll let you guys know what he finds.

I've got an '83 XS400k Maxim with 7500 miles on, that I'm having some issues with. Since I got it around for spring, I'm having issues with the engine once it's warm. Now, I should explain that I did have the carbs apart, but only for a cleaning. I didn't remove any of the needles, but I did replace the float valve and seat, and put new bowl gaskets on. Got the bike back together, fired it up... seemed fine, was running strong. Took it out for a ride, and immediately had issues. Bike would run fine up to 4-5k RPM, and then start spitting and sputtering. If I backed off the throttle to just maintaining speed instead of trying to accelerate, it would clear out and maintain 5k rpm. Any attempt to accelerate past this leads to the same result. At first, I was thinking that it was starving for fuel as a result of me knocking some chunk of something loose in the carbs. So, I get back to the house ,and pull the plugs. Both of them were as black as anything I've ever seen. Okay, so we're fouling. Thought at first maybe it was just because they're last seasons plugs, so I replaced them. New ones do the same thing. Once the bike is warmed up, the issue is able to be replicated even at idle. Give the throttle a crank, and sometimes it'll make it all the way to 7k, then start sputtering and slow down to around 4 or 5. Right now, I'm considering pointing my finger at the ignition system, only because I didn't touch any of the carb settings... just cleaned. One question is, does this bike have electronic ignition, or points? I know it has some electronics hiding here and there with heatsinks on them and such, but I'm not sure what type of ignition it has. Any thoughts from those more experienced that me?

I wouldn't have paid a dime. You rode it in, it was obviously fine. Whatever they did during the recall caused the problems, and they should be the ones to pay to fix it. Good luck getting a yamaha rep out there. Complain LOUDLY to anyone who'll listen and also those that won't.

That's a good thought.... I'll have to run out and get a can. I tried motor oil on the coils earlier today, but it didn't hang on long enough. Plus it makes a bit of a mess. I don't think the water should be too much of a problem on this, as the spring is nicely tucked up into the bike and appears to stay dry.

On my XS400K, I've been noticing a rear groan that occurs any time there's travel in the suspension. (This bike has the monoshock rear end). I took the seat and tank off, and traced it down to the coil spring and surrounds the shock. The body of the shock does have a plastic cover over it, that I'm guessing is supposed to prevent the spring from rubbing on the shock body. If I press on the top of the spring, the noise goes away, but I can still feel the vibration through my hand. Anyone have any tricks on how to get this to stop?

Okay, first of all... when I let the bike sit for a bit (ie- from when I get to work in the morning, until I go to leave for lunch), the right cylinder will load up and misfire for a bit until I get it cleared it out. usually I rev it a few times, let it idle while I put on my helmet, and it's okay after that. Well, while diagnosing this issue, I had my hand in front of the exhaust opening. It was then that I noticed that the right cylinder has a much more forceful exhaust "pop" than the left side. Even at idle, with both hands over the exhaust, it's quite noticible. What would cause something like this? I think I might be looking at two different things... one, the flooding, and two, the apparently imbalance of the cylinders. Is it possible that the right side carb is always open just a bit more than the left?

Here's three youtube videos of me running it out on the road Note- these videos were taken with no air filter on the bike. Therefore, performance and sound are not representative of the finished product.

Here's some shots of my old smoker. This bike was my dad's first motorcycle, which he purchased from my grandfather. It hasn't been on the road since '82. Engine was locked tight when I acquired it from my dad, but I stripped it down, had it bored .75mm over, slapped it back together, and the bugger runs. Actually runs pretty well, too... but it needs a lot before it's ready for the road. That project was put on hold due to buying a house, but I still fire it up every so often to make sure it's all still together. Pulled the engine Not so good-looking Ooh! Shiney! As it sits right now, complete with Vise-Grip shifter because of the shaft being buggered up. A quick paint spray, and some new tires, and she should be good as new!

I'm not sure how exactly you tell, but when I gave my dealership the VIN #, he said it was an XS400k. Mine is also a 1983 Maxim model, so maybe yours is the same?

Check the shift pattern on the bike. Below the shifter on the bottom of the engine cover there should be a shift pattern sticker. On my '83 XS400k Maxim, it's 1-N-2-3-4-5. There is no 6th gear, though I really wish there were, because like your bike, mine spins 5500rpm @ 55mph, and is pretty linear from there up. Gets a bit buzzy at higher speeds. But then, this bike wasn't built to be an interstate cruiser...

Are you trying to shift while the bike is running? Have it up on the center stand so the rear wheel can spin freely, and try to run it though the gears (letting the clutch out between gears). Is there any clutch drag? Put the bike into 1st gear, keep the clutch in, and see if the rear wheel spins on its own.