Proud owner of a "brand new" Maxim

[Lou Ranger]

Well, I took her out for a spin. Rode about 35 miles or so. I did notice that I had to tweak the idle screw after the bike was completely warmed up. I have had to mess with that screw the past few days including today. Would ambient temps have anything to do with that? After I have the idle set, though, it runs just fine. I can bet that tomorrow if I were to ride I would have to reset the screw again after it warms up.

LOL. Now this is starting to sound familiar.
Dave is certainly right about everything, and if you get your carbs as clean, and your bike as well tuned as his, the performance will amaze you.

I was luckly to get one that was already set up as close to perfect as I figured I could ever get it. It was all factory original - set up a little lean which was "state-of-the-art" for 1983 emissions control. I considered playing with the jets, but every time I rode it fully warmed up, it performed perfectly, especially after I got over my fear of explosions between 8 & 10k rpms.

But I did notice that when warming it up, if I pushed the enricher all the way in, it would sometimes stumble and stall. I could ensure it didn't do that by turning the throttle cable stop (on the right carb) a half turn to keep it idling at 1200. But then, when warned up, the bike would idle, annoyingly, at a higher rpm. For a while, I would turn the stop scew back and forth each morning. I didn't mind having it as part of the starting procedure, however, it was awkward with me on the bike at a stop sign with my gloves on.

And then one day I was possessed (again) by the spirit of MacGyver and I tried putting the stem of a little leaf in the stop's gap. It was wide enough to duplicate the half turn - which kept it idling while I got helmet and gloves on - and the moment I'd start off and open the throttle, the leaf stem would drop out and blow away. By the time I got to the stop-sign, the bike was warmed up enough to be set up perfect.

This high-tech, variable-throttle setting mechanism is not copyrighted or patented, so you may borrow it - no charge!

 

[Donkey]

Very cool, Donkey. Those are the same sizes I have on my ride right now. I am going to be selecting the Kenda Challengers for my Maxim. They seem to be a popular choice amongst other Maxim and XS400 riders. They are also a fairly decent price.
By the way, is there anything in the owner's manual about the warm period for the Maxim? My warm ups seem to take quite a while and I am wondering if I need to investigate something else.

I scanned the pages. I also agree a carb cleaning is the best thing anyone can do. I idle at about 1100. Also started it this morning after not riding for two days. Let it warm up for about 2 min then moved the chock all the way to the right and rode. Little sluggish throttle at first but by third gear I was gone.

 

[doodsaibot]

Thanks for scanning that, Donkey. My Kenda Challenger tires came in today. May have some time this weekend to get em on and check the sync/idle mixture on my carbs like Dave suggested.

 

[doodsaibot]

Gave my carbs another clean per Dave. I hooked up a vacuum gauge after getting my bike fully warmed up with idle at 1200. The needle on the vacuum gauge was flying all over the place. The tubing that I used to connect to the carb holders was a pretty tight fit. I am not sure what I need to do now. Help me, oh Great Ones.

 

[16VGTIDave]

You need to restrict the tubing so the pulses are damped. I use hose clamping pliers that are designed to squeeze the hose closed without doing damage, because I have one and it is easy to adjust. A pair of locking pliers and a piece of cardboard to protect the tubing would work. Adjust the pliers to squeeze and restrict the tubing until the vacuum gauge settles down, but still responds. The needle will still be fluttering, but just a bit.

 

[doodsaibot]

Alright, I restricted it with the clamping pliers and picked up a 6 in. Hg on the right carb (throttle cable side) and an 8 in. Hg on the left. I have a single vacuum dial so I was checking them both independently. In hindsight, I should have made a "T" and hooked up to both at the same time.

 

[TimKern]

Welcome! I guess I can say that, as I've just joined -- and I could use some help, too.

Yesterday, I bought my first XS-400, a 1982 Maxim, that's original parts except for mufflers and the rear turn signals. Many more miles (21k) than yours, and it doesn't run at the moment. It's below freezing here in Indy, so all I've done so far is charge the battery (it wasn't particularly low), check for spark (weak but there), and slosh the year-old gas in the tank to be sure it comes out the petcock. (It does.) Turns over fine but makes no effort to bark.

I have ordered new spark plugs; they'll arrive Monday. (How many calories from Thanksgiving do you reckon I'll burn, changing spark plugs? Maybe half a cranberry's worth?)

Can't seem to find any info on the DOHC engine or pretty much anything else on the monoshock model; all the manuals I see here are SOHC models. Anybody?

 

[Lou Ranger]

Welcome! I guess I can say that, as I've just joined -- and I could use some help, too... all the manuals I see here are SOHC models. Anybody?

Nice choice . Welcome to the Forum. Post #3 here: http://www.xs400.com/forum/showthread.php?t=4503, should have everything you need.

... and slosh the year-old gas in the tank to be sure it comes out the petcock. (It does.) Turns over fine but makes no effort to bark.

And it won't. First thing, get rid of ALL than year old gas - run it through with a full tank in your car if you have no convenient way to dispose of it.
And install an in-line fuel filter for $3 so none of the detritus in the slosh can get into your carbs. It might be too late, but you could get lucky if you don't try and start it again without first purging the bowls, lines and tank.

Check out this thread: http://www.xs400.com/forum/showthread.php?t=10595 , and go through the key items first, even though it hurts to be patient and cautious. You will avoid much frustration in the long run.

 

[TimKern]

Nice choice . Welcome to the Forum. Post #3 here: http://www.xs400.com/forum/showthread.php?t=4503, should have everything you need.



And it won't. First thing, get rid of ALL than year old gas - run it through with a full tank in your car if you have no convenient way to dispose of it.
And install an in-line fuel filter for $3 so none of the detritus in the slosh can get into your carbs. It might be too late, but you could get lucky if you don't try and start it again without first purging the bowls, lines and tank.

Check out this thread: http://www.xs400.com/forum/showthread.php?t=10595 , and go through the key items first, even though it hurts to be patient and cautious. You will avoid much frustration in the long run.

Thanks! OK, you're right -- I tried to jump over too many steps. Got her running today, then drained all the fuel and ran her dry. Will address additional items step by step. It's more encouraging when you know it has enough of the parts in good enough order to make heat.

Now I can settle down and work, knowing that ultimately she'll be better than ever.

Next, I'm going to think ahead a bit and locate a valve cover gasket and see what bucket shims I may already have from something else (GSXR?), in case I need to adjust anything. Don't know diameters and thicknesses yet, but I will, after I read the manual (for thicknesses) and measure one (to see the diameter).

What's a good source for valve shims?

 

[16VGTIDave]

29mm diameter shims. Same as used by Kawasaki in their KLR 650, and in some BMWs. NOT 29.5mm! The valve cover gasket is rubber and can be reused without issue. I decided to buy a shim kit as it wasn't worth my time to calculate the required shims, drive to dealer to order, wait a week, and drive in again to get them.