Topic: 1978 Supersport not starting

[Cold Mountain]

Hi all

I have a 1978 supersport.  I worked on this bike last year and it was running fine (opened up and cleaned the carbs, did the valve adjustments etc).  I let it sit for a few months.  Recently, I have tried starting it and its not starting.  Here is what I have tried:

-battery is fully charged
-Fuel is going from tank to carbs
-There is a spark in the spark plugs

When I try the electronic start button, nothing whatsoever happens.  When I do the kick start, the engine doesnt seem to roll except for a couple of times.

I am a total novice/green mechanic as you can probably tell from the post.  Is there any guidance you can give me on what I should look at next?  Ignition coils? points?  And how to go about it...?  I have the Clymer Honda manual but there is not much that I can tell about debugging coils etc in there. ...

Any help much appreciated!

[MoMo]

The gas in the float bowls is probably bad-drain the float bowls and let fresh gas flow in.  Are you saying the electric start button is not working?...Larry

[Cold Mountain]

Yep thats what seems to be the case (electric starter not working).  At this time, I am just focusing on getting it kick started.  I will try draining the float bowls.

[MoMo]

Yep thats what seems to be the case (electric starter not working).  At this time, I am just focusing on getting it kick started.  I will try draining the float bowls.

the gas seems to go bad very quickly in the bowls.  Keep us posted...Larry

[Cold Mountain]

Hi

I drained all 4 float bowls and still no dice. 

[FuZZie]

When I try the electronic start button, nothing whatsoever happens.  When I do the kick start, the engine doesnt seem to roll except for a couple of times.

could you explain a bit better what's happening on the kick?

[Stev-o]

First off, welcome.

Ok, you have gas and spark, when was the last time the bike ran?
Try jumping the solenoid with a screwdriver, this should get the motor cranking.
It's behind the left side cover on my K4.
Look here, it's #9...


http://www.powersportspro.com/pages/OemParts?aribrand=HOM#/Honda/CB750F_A_(78)_MOTORCYCLE%2c_JPN%2c_VIN%23_CB750F-2200001/BATTERY_%2b_REGULATOR/CB750F-78-JPN-A/2Y134102F13410226A

[BeSeeingYou]

Is your headlight out?  The starter switch is a common age failure point and the headlight is routed through that switch.  Even with a bad switch it should kick start but you probably won't have a headlight.  Work back from the starter by first jumping the main contacts on the solenoid with a large gauge wire or screw driver to eliminate the starter as the problem, you might get a spark or two.  Next check the solenoid with a voltmeter and see if you are getting 12v on the yellow/red wire when you press the starter button.  If your starter was good from the previous test and you have 12v at the solenoid on yellow/red then it's the problem.   If no voltage then the starter button is the likely culprit.  Check out and download this wire diagram if you haven't already.

http://www.sohc4.net/?p=3514