PopMac's XS400 Maxim Cleanup

popmac

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Starting a thread now but updates may or may not be slow - we'll kind of just have to see how things go.

I bought this bike early this week and it's my first bike. I have absolutely no mechanical knowledge at all but can work with my hands, can follow instructions, have the manual and have a buddy or two who will help me out when I need a hand.

So heres the state of the bike and what I'm going to be doing:

Mechanically, the bike has some issues but I believe most of it can be fixed by cleaning out the carbs.

1) It has some problems starting up and getting running. It will start up with the choke wide open and the petcock set to prime, let it run a moment then change to run, but it revs up to 5k+ and doesn't idle down. If I let it run for a bit then close the choke a touch it'll rev down then sputter out. So to actually get the bike running I have to sit and baby the choke, moving it back and forth to keep it reving not too high or too low. Depending on the day I *may* at this point (five minutes+) be able to close the choke and keep the bike running or it may die. Once it's warm I can start the bike with the choke closed by starting in prime, waiting five seconds, moving the petcock to run. Even once the bike has been going for a good while and the engine should be good to go, I always have to set the petcock to prime and let it run for about five seconds before I can get it going.

2) Occasionally the throttle goes nuts / the engine revs up out of nowhere. This happened once in gear as I was riding around and a couple times while running in neutral. No idea what this is about.

3) While running the bike will occasionally stall out. This can happen in neutral but I adjusted the idle throttle screw and fixed that for the most part, but it also can happen in gear with the clutch fully pulled in, so I don't know what that is yet.

3) Horn doesn't work

4) Turn signals occasionally work properly. They always turn on but sometimes they blink and sometimes they are just a steady light on.

5) Rarely I can't change gears. This may be related to stalling out? Clutch issue or even just a cable issue?

I think that's all for the big things.

Cosmetically there is work to be done but I don't know exactly how deep I want to go yet. The previous owner painted everything black - exhaust pipes, engine, forks, etc. I like the look of this, but he did a pretty crappy job. So I'm going to strip everything down and do it all properly. The tank is stock and looks fine but reading around on here I've seen a couple builds with knee indents and I love the look of that. In addition to that I may paint with white stripes down the middle, like seen here - http://www.xs400.com/attachments/img_20160813_083251-jpg.27322/ - but at that point I will most likely pick up a used tank off eBay and mod that one. If I make some mistakes and mess up the look of the indents I don't want to be SOL. I also really love the look of a matte black instead of a gloss, so if I need to think on how i want to do the tank before I start doing everything else.

So, those are my thoughts. I won't have my license until fall and probably won't safety and insure until next season, so I have time to get everything sorted.

Feedback and suggestions extremely welcome. Here's a dump of photos, including a bonus pic of my works parking lot where I will ride around (mostly in circles) until I can take it on the road!
 

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Got the horn fixed - cleaned the contacts and tightened up the screw on the back, works like a charm. Moving on to stripping, using a wire cup brush and a drill. For the most part it's coming off very easily. Time consuming, but easy.

Now I see why the previous owner painted... Next step, figuring out how to go about removing all the rust, if I can / if it will make a difference. I stripped a small portion of the other exhaust pipe and it doesn't seem to be nearly as bad as this one. I haven't decided yet if I want to paint everything again or try to clean it all up and go back to original. If I want to paint again is the rust as is an issue?
 

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First welcome to the forum, always happy to see DOHC on here.
When idle hangs and then stalls , aside frome the carbs it usually is vacuum related, i.e. check your carb boots for leaks by spraying brake Klean or something combustible around the boot area...engine will rev up...
Sometimes the little caps on the vacuum ports get dislodged...or the little oring that fits between the head and boot gets pinched...etc...
And it goes without saying...clean and I mean REALLY clean your carbs, add an in line fuel filter for good measure,plus a little seafoam doesn't hurt.
Fresh oil helps, and you get the chance to check the old oil for debris or the smell of gas from leaky pistons...
 
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When painting,prep is key,the best is media/sandblast.
I used sandblast on my build, VHT paint oven cured and happy to report that I rode on gravel roads this weekend and the paint held great (no chipping whatsoever)
Headers are painted with VHT (for rustproofing) then wrapped.
...as for what to do with it...
Do what you want and do not let people tell you it can'take be done...
I built a dual shock scrambler AND a monoshock cafe racer based on the Maxim/Seca
Anything is possible with time/money...patience and help from the gurus on here.
 
First welcome to the forum, always happy to see DOHC on here.
When idle hangs and then stalls , aside frome the carbs it usually is vacuum related, i.e. check your carb boots for leaks by spraying brake Klean or something combustible around the boot area...engine will rev up...
Sometimes the little caps on the vacuum ports get dislodged...or the little oring that fits between the head and boot gets pinched...etc...
And it goes without saying...clean and I mean REALLY clean your carbs, add an in line fuel filter for good measure,plus a little seafoam doesn't hurt.
Fresh oil helps, and you get the chance to check the old oil for debris or the smell of gas from leaky pistons...
Thanks for the welcome!

I'll check for leaks this weekend, hadn't read that. Seafoam didn't seem to do anything, maybe it helped a little bit that could also be reaching on my part and oil is good. A really good carb clean is in order and coming soon(ish). The full carb clean will be done with help from somebody who has done this many times, so it's just a matter of when our schedules line up.

I used sandblast on my build, VHT paint oven cured and happy to report that I rode on gravel roads this weekend and the paint held great (no chipping whatsoever)

I'm looking into sandblasting soon, I have no idea what the cost on that will be. For sure I'll be sandblasting the engine so I'm going to call and get a price on that, then also get a price on doing all of it and seeing if it's worth it to me or if I just want to do it myself. VHT paint is what I was going to be using, though. I had a talk with a guy at my local auto paint shop and that's what he strongly recommended.

Do what you want and do not let people tell you it can'take be done...
I built a dual shock scrambler AND a monoshock cafe racer based on the Maxim/Seca
Anything is possible with time/money...patience and help from the gurus on here.
Oh, I know. Generally I see people say that not too much can be done with the Maxim when compared to the SOHC models but I read all the way through your Maxim cafe racer thread a couple days ago and was really impressed! Time and patience are fine, money is... lacking. But that's okay. While I would really love to do something like that down the line, when I said I'm not sure what I want to do with it I specifically just meant the finish. Try to restore back to a nice shiny chrome, paint it, paint the tank, maybe do knee dents... that's about the extent of it for now. This is my first bike so the big thing is getting it running nicely and riding the hell out of it. The easy cosmetic stuff that previously looked like crap will be taken care of, but everything else will wait until after next season.

Quick other question for you, seeing as you probably know - how does the gasket fit with the exhaust pipes? When I removed the pipes yesterday the gaskets just fell out and I can't seem to find where to properly put them... looking at 3-2 and 3-3 in the manual it just says to remove the bolts attaching to the cylinder head and remove the pipes... can't seem to find an exploded view of how to put it back together.
 
Since they fell out maybe look into changing them as they are made of soft material that gets squished behind the headers.
You just need to hold them there...it might get finicky...sometimes i use a dab of multipurpose grease so it sticks in place whilst I put the headers back on.
 
Since they fell out maybe look into changing them as they are made of soft material that gets squished behind the headers.
You just need to hold them there...it might get finicky...sometimes i use a dab of multipurpose grease so it sticks in place whilst I put the headers back on.
Looking at replacement gaskets for the bike, I'm no longer sure if I'm talking about the right part. Is this my gasket? Damaged? Or is this something else..
 

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The gasket is the oring on the head...these are just the headers flanges...they do not look like they are damaged.
 
That's extremely helpful and exactly what I was looking for, thanks. Where did you find that? I'm assuming there's a legend with everything labeled to the numbers? Would be useful to know the names of parts to communicate better.
 
Awesome, thanks guys.

Got the exhaust pipes stripped and back on the bike for now. Looking into options to get rid of the rust but otherwise bike work is on hold until next weekend when my JIS screwdrivers show up.
 

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The only way to go without stripping the sh.t out of everything
Previous owner already has that covered. Probably going to have to replace a few of them but I won't know if they are as badly stripped as they look into I get the driver in.
 
If you replace..I went with stainless steel allenheads. Makes for easy install/removal
Not a bad idea. There is one replaced with a hex screw, was quite nice. Do you use them for everything?
 
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That looks like it could use a good cleaning. Or maybe just get a new one and wire it in.
 
For sure needs a cleaning. If I can find the ends for cheap I'd just replace them. But people here seem to frequently replace the full box with other ones. Not really sure why they do that or what the benefit is though.
 
Well my electrical looked like a birds nest.......someone spliced in who knows what over the years. I am just starting over from scratch on mine.

I think some have went to the newer fuses also.
 
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