My xs400... Running, but not road-worthy.

Ruined1

Ruined1

82 Maxim xs400 Owner
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My xs400... Running, AND FINALLY ROAD WORTHY!

So I bought an '82 Yamaha Maxim from some guy locally. It looked like Barney. :(

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I got it and it ran pretty smooth, freshly cleaned carb (looks ultrasonic clean when I opened it up :thumbsup:) and re-jetted. The only problems were a worn back tire and bad teeth on the sprockets so I pulled the tire back some and was cruising. :bike:

Not a month later... The trouble started. :thumbsdown:

The back tire blew out one morning, luckily not 50 feet out of the driveway. It sat for two days. I finally got the time and took off the back tire and got it up to the shop. While it was at the shop I took it upon myself to do a little spray painting... Yes this immaculate job was out of spraycans...

Photo0385.jpg


So I put the tire back on and the axle bolt wont go all the way through (just a 1/4 inch wouldn't slide in :doh:

I decided it was tightened down well and that I would ride it up to the shop the following day. I wanted to start it though and take it down the street just to test the tire...

"CHUG-ah-CHUG-ah-CHUG-ah-CHUG-ah-whirrrr...."
"CHUG-ah-CHUG-ah-CHUG-ah-CHUG-ah-whirrrr...." :wtf:
"CHUG-ah-CHUG-a-VROOM" Ran then died...
"CHUG-ah-CHUG-ah-CHUG-ah-CHUG-ah-whirrrr...."
"CHUG-ah-CHUG-ah-CHUG-ah-CHUG-ah-whirrrr...."
"CHUG-ah-CHUG-a-VROOM" left it almost open throttle... still died.
"CHUG-ah-CHUG-ah-CHUG-ah-CHUG-ah-whirrrr...."

Damn! Go to get off the bike and diagnose the problem... Unfortunately I didn't see the huge oil puddle under my foot... "OH SHIT *SMASH" and to the ground she went :mad:
To top it off, the gas tank leaked while it was on it's side and ruined the freshly painted gas tank for a paint job that took me hours :banghead:

Turns out the clutch push rod seal went bad...

Photo0386.jpg


So today I picked up the oil seal, an oil filter, and oil as it appeared there might be a small trace of gas in the oil... Not much just a whif... but enough to alarm me. I also put on order for my drive sprockets, the rear axle bolt and locknut, and a fancy new oil cap since mine is missing one of the two grab points to open it...

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On top of it the left (main) cylinder won't hit right at low rpms... like not at all... only semi-open throttle and up... The plug has been replaced twice due to fouling and I adjusted the float for the carb to that cylinder as it was at a totally different setting from the other float... aka retarded mechanic syndrome to whoever the previous owner took the bike to for a carb clean/rebuild...

So tomorrow I am replacing the oil seal and changing the oil/filter/cleaning sump screen.

List of things to do before bike is returned to "Badass Classic" status:

1) Fix oil leak
2) Change oil/filter and clean screen
3) Replace sprockets and oil cap
4) Replace rear axle bolt/nut
5) Figure out why the left cylinder isn't hitting and i'm getting 20 mpg...
5b) Referencing this link Carb Tuning to hopefully solve that issue.

So now I have a semi-intro about my bike... Here's "About Me":

I'm 20 years young and have years of experience riding... My cars have never been in the shop for anything unless I couldn't do it because of machinery (Tires, Wheel-Align, etc.) but I'm new to the bike scene. I love my xs400 and will have it for a long time if I can get/keep it running.

Now that both intro's are done, if Anyone has any information regarding the "Mysterious Missing Cylinder" or any other issue I'm having I am ALL ears :D

So glad to be a part of this community :wink2:
 
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As the rear wheel goes,there are spacers that have to go back together correctly or there will be problems like you had when you put it back together. If you haven't done so,get a manual,and it will show you how it is assembled. The carbs on these bikes are kinda finnicky,and must stay clean or the bike won't run right or at all. For this reason,you should always run a good in-line filter,clear if possible.Also the petcock[gas valve]is vacuum actuated and opens when started. They are old,and sometimes need to be rebuilt or replaced. Download the manual on this site and you'll have a good reference for problems when they arise.Good luck. lha
 
Welcome to the forum. I have the same bike, '82 xs400 Maxim. About the missing cylinder, as lhaolpa said, could be carbs. Another possibility is the pick-up coils are dirty/bad. Not sure if that would help, mine were filthy and made my bike run like garbage. I see you have mechanical experience, but I'm new to the bike thing too and this took me about a month to realize 'cause it's different. Hope this helps and good luck.
 
Maxim-umm said:
Another possibility is the pick-up coils are dirty/bad.
Click to expand...

Yea but are your coils built INSIDE the frame underneath the gas tank like mine are?...
It's rediculous I don't even know how to get at them... Paging through the manual...
 
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I still can't figure out how to get at the coils... I've suspected them from the beginning and I am frustrated to no end... There's no way they're going to put coils and spark plug wires up into a piece of welded frame and have no access to them... it doesn't make sense...
 
I think Maxim-umm is talking about the "pickup coil-governor" located on the left side of the engine, under the domed cover with the screw-out plug in the center. Kind of the electronic substitute for points, I think.
 
I would also ensure your battery is up to it. if its low then the TCI won't be cranking out the amps. happened on my tracker as it was only firing one one cyl (sounded good though) and the earth lead to the TCI was on 1 strand. Solderd that up and no more problems :D
check all your earth straps for metal to metal contact

carbs will need stripping and cleaning too methinks
 
drewpy said:
A) I would also ensure your battery is up to it.

B) carbs will need stripping and cleaning too methinks
Click to expand...

a) I never thought about the battery... He did just have it replaced not long before I bought it... but did they replace it with a strong enough battery :thumbsup: ... I don't even know where all the grounds are but I'll look around the frame. :shrug:

b) I opened the carbs not long ago to check the floats, needles (which i cleaned), etc... That thing was immaculate inside... :yikes: Shiny and beautiful like the guy who did it ultrasonic'd it... I'll crack it open at some point and take some pics... Off to change the seal/oil now that im done working =)
 

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