Need help getting XS650 to run

[darrell650]

i have a 1980 xs650 yamaha chopper i replaced the head gasket on it and double check the timing and i am dead on. Then i check the carbs and took them apart and cleaned them. Then when i put them back on she fired right off ran good for about 20 min. then died on me . Now everytime i try to start it up again it back fire through the carbs and exaust. Some body please help me i am new at this and all i want to do is be able to ride. So if any one out there can help me that would be so gratefull. Thank YOU signed... Darrell....

 

[XSLeo]

When you had the carbs off for cleaning, did you clean out the tank too? Any crud in the tank will get into your clean carbs and plug them up. I might pull the carbs and clean them again. Remove the tank and clean it out too. While cleaning the tank, pull off the petcocks and clean them too.
Use inline fuel filters.
Check to see that the carbs are still in the holders and the clamps are tight, tight enough so the ends touch where the screw goes through the clamps.
Check the holders for wear and cracks. Air leaks cause many problems.
Have you read www.amckayltd.com/carbguide.pdf ?
I might also go through the basic tune up checks
Cam chain tension,
Valve adjustment.
Ignition timing.
Do these things in that order. They may be ok, but checking them eliminates them from the list of possible problems.
Leo

 

[scabber]

Check the barbs you could have lost a vacuum cap.

 

[darrell650]

okay i have a xs650 that i put a new head gastket in and i cleaned the carbs also. since then i reaset the vavles and set the carbs but no fire the coil is good tested it. So my question is ive done all that i no but still no fire so i need help PLEASE some give some advice that will help and get this chopper to fire......