Introduction and Advice Needed, for 83 maxim XS400

Nat X

XS400 Enthusiast
Reaction score
Chicago IL
Hey Y'all, the names Nate and I just wanted to introduce myself and also use this thread to ask some questions and get some advice. I promise to use the search function as much as possible, but sometimes you just gotta send it.

So last week I picked up my first project bike, a 1983 Maxim XS400. It is definitely a fixer upper, but I was looking for my first street bike to be a bit of a project. The bike needs a battery, a big time tune up (carbs for sure and maybe some gaskets as there seems to be an oil leak), plus all sorts of other maintenance for sure. But when the bike is hooked up to a power source the lights and electric start all work, plus the motor is turning over so I feel pretty good about that.

But where to start is the advice I need from y'all. I live in Chicago and winter is coming.

Should I try to put in the work real quick and get it started, then winterize it? I really think I could get it start if I throw enough time and $$$ at it. But it would be a rushed job.

Or should I drop the motor, bring it into my home and do an over the winter table top rebuild? I could then find an indoor home for the rolling chassis to sort out all the non engine issues. I'm really leaning towards the 2nd option, as leaving the bike outside all winter would drive me crazy! Plus I wanna get my hands dirty over the winter and ride once Chicago thaws out in the spring.

Thanks in advance! And I attached a pic of the bike after I pushed it over a mile home the day I bought it!


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Welcome. Youre aware of what the bike really needs so thats a good start. Winter is coming and I know you guys get it hardcore over there lol.

You should do is a compression test. I dont really trust a compression test when the engine hasnt run in a long time though. I would never take an engine apart unless I absolutely knew it was bad. Never break the factory seal unless you have no other choice.

Im going on a whim here but I say the engine is 100% healthy lol

The bike turns over, thats huuuge. Spray a fogging oil in the cylinders and put the plugs back. What I also do is spray fogging oil into the exhausts and then stick a loose paper towel in the ends. I remove the carbs and fog the intakes and stick a paper towel in the boots. Remove the valve caps and dump oil on the lifters and cam(s). Battery and carbs come inside the house along with the gas tank which is also emptied and fogged.

I think that is the best approach. Dont rush to rip everything apart randomly. Dont tear into the engine at all, leave it alone. Get the paperback shop manual and read it thoroughly and youll be able to rebuild the carbs over winter and collect parts.

Aside from the engine. You need new tires and replace the brake lines and flush it all out and get that taken care of. Other than that, the bike looks like its in good shape and you will enjoy it just as it is. I have all these other big bikes and the XS is my favorite one to hop on. I really enjoy the <500cc bikes and I think theyre highly underrated. I recently picked up a Honda CB350 lol.
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Thanks for the advice NewHavenMike!! I think your completely right about the compression check. I'll have to try and bang that out before the winter sets in. I'll be posting again for multiple questions in the future, plus I plan on starting a build thread when I get wrenching as well!
Welcome to the forum Nat and congrats on the new 1st project! Like lots of us you will probably eventually have projects #2 and #3 making their way to you as you get better mechanical skills and knowledge.:bike:
Depending on your locations could you find a storage unit to get the bike to? If you can get one, especially with power (for heat and tools), you can use it as a temporary workshop to get everything going. I would say if your compression test is good based on NewHavenMike's suggestion, you might just need a good carb cleanout (possible carb part replacements) to get the bike running. Also don't forget to check/buy sparkplugs, NGK's are pretty cheap and it removes some the variables when troubleshooting.

Once you get the bike running, really it's up to you as to what is next. You'll probably have a a functional bike, but you'll need a few more things before it's safe/legal. I agree with NewHavenMike, focus on making sure the brakes are in good shape (purging the lines, seals if necessary). You might also need new tires even if your tread looks ok, check the age of them and if it's > 10 years go ahead and replace them as rubber doesn't like sitting for that long.
Thanks for the advice pcream! I'm going to do the compression test next Monday, and we will see were to go from there. I'm going to look for a garage spot to rent or maybe even look for a Motorcycle Co-Op in the city. And as far as your recommendation for carbs, brakes, tires and other general maintenance... I'm going to go balls deep on this mother f'er!! Plus I got all winter to collect parts and handle the tear down and tune up. The bike needs lots of love, but I think it has good bones and will be worth it for sure!
So finally got around to doing the compression test today. Before I completed the test I pulled the carbs, exhaust and tank. I also fogged the motor. I got 140psi on both cylinders, which I hope is good!!
140 is still ok, but did you do it after you fogged the motor? If you did it after the oil it would raise the numbers by quite a lot.
140 is still ok, but did you do it after you fogged the motor? If you did it after the oil it would raise the numbers by quite a lot.
Ya I fogged it last week. I figured it might throw the numbers off a little. But I'm pretty happy that both cylinders are showing consistent numbers.
Great looking bike, I also just picked up an 83 Maxim. I get it today! Hope your build goes smooth over the winter. Are you planning on a restoration or conversion to something else? I'm only an hour away from delivery of mine.... can't wait!
Great looking bike, I also just picked up an 83 Maxim. I get it today! Hope your build goes smooth over the winter. Are you planning on a restoration or conversion to something else? I'm only an hour away from delivery of mine.... can't wait!

Thanks Addison! I'm going to collect parts and probably build a flat tracker inspired street bike, that is if everything goes according to plan! I saw your thread and was about to comment on it.....
Can anybody help me figure out the handle bar size for a 83 Maxim XS400? I'm pretty sure it is 7/8, but I just want to double check before I order my handle bars, clutch lever and grips this week!
Spent the afternoon yesterday wrenching on the bike and fitted my new flat tracker bars. They feel and look great! But when I was moving around the controls I noticed this weird little sensor thing. Any of y'all have a clue on what that thing is? It was wired up towards the left hand controls, but I can't find and sort of connection spot.

these bars look sick! Way better than the silly chopper style stock bars!
@Nat X I also noticed that same sensor on my bike this weekend.
It is on both sides of the handlebars. On the right, it connects to the back of the brake handle and is a closed circuit sensor. When you depress the brake lever, the little plastic piece on the end of that attachment is then allowed to fully extend, which closes the circuit and engages the brake lights.
I have the same one on my clutch handle, although I have no idea what it is for.... as obviously nothing 'lights up' when you depress the clutch. Would be great if someone could chime in!
I went for my first test ride this weekend... and I'm surprised how hard this bike pulls. As a big guy, I didn't think it would move me like that. Very impressed with the power.
@Addison Could it be a Clutch sensor? Found this on the internet
"Clutch sensors, also known as clutch switches, are a safeguard built into many modern cars and motorcycles. They exist to prevent an engine paired to a manual transmission from being started in gear."

Maybe this explains why my bike won't start? Cuz my clutch lever assembly is definitely not stock.
Yes it's the clutch safety switch. If you just unplug it from the harness it would be just as if you where to pull the clutch lever all the time. Lots of people just remove it where they go bad. If it still works it would be a good safety devise. The dohc xs400 also has a side stand switch that will lock out the e-start if your kick stand is down.
@xschris Thanks for the reply! I keep learning new stuff from this forum everyday! I didn't know about the kickstand switch, I was totally trying to start it on the kick stand!