Topic: 1982 650 SC Nighthawk will crank but not start

[82650sc]

82 nighthawk won't start. The carbs are getting fuel, the spark plugs are new and getting spark, the battery is fully charged. I am wondering what else could be the issue. There are a few tubes near the carburetor that are not connected to anything, could that be the issue or are they just breather tubes? Note: My petcock is broken. Could this lead to the engine being flooded?

[eigenvector]

I have an '84 CB700, don't know how different the carbs are - but something I learned from it was that it simply wouldn't start without the vacuum petcock fully installed.  Same with my '83 Sabre.  They appear to need the petcock installed properly.

If the openings you mentioned are what they are on my CB700SC, they're just vent tubes and aren't too important.  On California models, the '84 had an EGR type device hooked to the carbs as well

All said and done - confirm that the petcock is installed properly, other than that ensure the enrichment circuit is working properly - the springs can get sticky.

[82650sc]

Thanks for the input. I did unsrew the petcock. Maybe I messed something up.

[eigenvector]

Ah, I just looked at the carb diagram for your model - it isn't the same carb  as the '84.  Sorry, no help to give you - it's a pretty standard choke carburetor.  Looks like you just didn't do a good enough job cleaning it.
Terrible advice I know, but cleaning that carb can be a real bugger.  I have a similar one on my CB750 Limited and it was a real pain to get cleaned.

[Honda550k]

Compression? You need spark, fuel and compression for an engine to start.

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[purplechickenweasel]

The carbs may be getting gas, but they may not be getting it to the motor.
With the air box off, you could spray a little starting fluid into each carb, and turn it over.
If it almost catches, then reclean the carbs, check the cross holes in the slow jets, and the main jet holders.


Pcw