Yamaha XS400 Won't start

[plchamb]

Alright... now it is starts with the choke
but i think it is very sensitive to cold.
This afternoon... it was running good and tonight (colder but not that cold --> 40 F) and it is having problems... well as soon as i open the throttle a little bit.. it dies on me.
Any suggestion? carb problem?

[storysunfolding]

If you really open the throttle fast you might be losing the vaccum... but chances are that you didn't clean all the circuits well in teh carbs. Take them apart again and make sure you get all the little passages clean. It may take a small piece of wire to get through the smaller channels. I recommend taking a vaccum cap (80 cents at most) and drilling a hole just smaller than the tube you get with the carb cleaner. Push the cap onto the tube and then when you spray down a passage, push the cap up so the rubber on it blocks the passage directing the force from the carb cleaner directly down the passage.

[kar_the_terrible]

if its running with the choke on but dies out without it.. then its probably the carbs. If you've only cleaened them with the spray cacn carb c leaner, you might need to do it multiple times and with multiple cans. The best thing to do is to buy a can of carb dip, REMOVE ALL rubber/plastic/nonmetallic attachments to your carbs and leave the carbs in the dip.

You'll get superclean and super shiny carbs.