XS400 crank but no start

[Jordan Vogt]

Hi guys!
Im new to this thread and didnt know where else to turn. Long story short Ive always wanted to have a cafe style bike and recently aquired a 1981 xs400 maxim. Now ive been working on cars for years but mainly modern cars and dont know my way around carbs all to much.
So i got this bike last week and the guy i bought it from said it hasnt ran in a while, i have spark when i ground it to the frame, ive tried spraying starting fluid in it and it does nothing. Aside from an occasional backfire when cranking. Also tested both cylinders for compression and got 130 psi on both. Not the greatest compression but i belive it should at least run. Now the gas could be bad but i did shut the gas off and tried starting fluid and nothing. Any help is appreciated!!

 

[got20z]

I would suggest taking the tank and carbs off and cleaning everything well. Also clean the air filters or replace them (if they need it). Put it back together and try it again with fresh fuel. Since you have spark that is a good sign. If the bike has been outside or stored inside for a long time with risk of mice, rats, bees, etc. I would also take the exhaust loose and check it for buildup or obstructions.

 

[NewHavenMike]

Welcome.

READ the manuals and use the proper tools.. DONT take anything apart if you don't know what youre doing. The carbs probably/definitely will need to be cleaned and will have to be absolutely spotless even when you think they are clean. I use an ultrasonic cleaner for carbs.

Keep in mind that parts for these bikes, and the carbs are expensive so you really need to keep everything in order and reusable. Don't mash the wrong size screwdriver to a screw or brass fitting.

At the very least, order new fuel line and an external filter. Id probably pick up some mineral spirits or something like that which is solvent based and slosh it around the tank and clear out any crap that might be in there, and then verify proper flow out of the petcock. Then you can work your way down the fuel tract.

You should be able to pour some gas right in the spark plug holes and get it to kick over a couple times. Get new plugs too, NGK BP7ES.