82 CB750sc spark and fuel no worky? Need assistance!!

[cflipper]

Hi everyone. new to the forum and could use some assistance. Just getting ready to start a build on a 1982 CB750SC nighthawk. i picked the bike up this week the previous owner said he had it running a year ago but did nothing with it since and he hasnt had it running since either.

So this is where i step in i have
(1) drained all fuel from tank replaced with new.
(2) cleaned jets and emptied bowls on carbs and checked all fuel lines going to carbs all are clear
(3) checked plugs for gap and spark
(4) made sure all plug wires are in proper sequence
(5) Tried starting with a shot of ether as well and still nothing

so from the things that i have done i fugured that i do have spark and the bowls on the carb have refilled so it seems that the fuel system is clear and running.

the battery is dead and i have tried starting off a battery charger/starter

So i am not sure where to go from here i am in need of assistance.
thanks ahead of time

[Piute]

  I can say this Your going to need a batt. car batt best takes longer to drain.And great for setting out of way.

[shinyribs]

Welcome!

The carbs can be finicky. The best way to make sure you are infact getting fuel to the cylinders is to pull the plugs and make sure they are wet.

Clean white plug that is dry-no fuel

Clean white plug that is wet-fuel,but no spark.

These bikes demand a strong battery for proper spark.Just a necessary evil. You might have to start there actually. AGM batteries and the such are nice,but if you are on a budget then lead-acid batteries aren't all that bad. I picked up a lead-acid for my 76F for under $40 and it still cranks strong.

Good luck man. See ya around

[LukeM]

You _can_ use a car battery and jumper cables to jump start a motorcycle.  However, do NOT use a running car to do this.  The current from an idling car alternator can go over 50-60 amperes, which will blow a great deal of the motorcycle's electrical system (fuses, reg/rec, headlight, etc).

Luke M

[cflipper]

well today i got it running  now i can start concentrating on other things. i did end up jumping it  and giving it a quick shot of ether.  the big thing that i fixed was that one of the carb intakes was off. Due to me working on it late at night and i wasnt thinking straight by the time i was done    after warmed up and choke is off it seems to creep up to 2500 to 3000rpm and sit there. i tried the idle screw and on new start before i give gas it sits at a good idle speed and after i give it a shot of gas it sits at high rpm again.

any suggestions would help

[cdaiscool]

Read the FSM and tune the carbs. Also, whenever you are having issues getting it to run, always check over the basics. 95% of the time, that's what it is all the time.

;)

[shinyribs]

The two biggest causes of a creeping idle are

1-vacuum leak <----usually the culprit
2-flooding

1-Vacuum leak is usually found at the carb boots. Either they get cracked,the clamps are loose or they are just too hard to seal properly.

Cracked- you need new ones
Loose clamps- self explanatory ,but easier said then done.They can be a dog tighten.
Too hard-supposedly boiling them in wintergreen cures this. I have no experience here,but use the search bar on this site and you can find lots of info on this

2-Flooding caused by sinking floats or sticky float needles. Too much gas enters the motor and the rpms go up trying to burn it off.