Topic: Engine turns over for a few seconds then backfires loudly, still doesn't start

[verro]

1981 CB650C

-Done a full carb rebuild
-Engine turns over nicely
-Fresh oil

Got the rebuild done today to see if I can get it to start (Never seen it running, supposedly it ran last November)
I know the reason for the backfire is that it was running rich, and when i tightened the carb screws it didn't backfire but it still wouldn't crank.

I know the engine is getting air and fuel, so spark must be what's wrong, correct?
I do not know about compression but I'm going to assume its good.

I don't have a socket for the plugs so I haven't been able to check them, should I go and buy a socket and some new plugs? This would be the most likely cause.

I just don't want to #$%* up the motorcycle or anything. Don't want to cause damage I literally cannot afford.

[dave500]

man go get a #$%*ing plug socket for #$%*s sake,then you can see the plugs condition and if they have spark.

[newday777]

1st thing, is the spark plug socket and get new spark plugs(NGK ONLY)
Get a compression tester from AutoZone ( they have lending tools)

[TwoTired]

Turns over nicely or…
Won’t crank.
Which is it?
Have Fresh battery? Fully charged?

Back fire from carb intake, or exhaust?

Engine built by Honda or someone else?

Check spark plug tip for combustion conditions.  The see if they spark.

Checked tune up procedure in shop manual?

[verro]

1st thing, is the spark plug socket and get new spark plugs(NGK ONLY)
Get a compression tester from AutoZone ( they have lending tools)

This is what im planning on doing. Thanks for not leaving a snarky reply 

[TwoTired]

1st thing, is the spark plug socket and get new spark plugs(NGK ONLY)
Get a compression tester from AutoZone ( they have lending tools)

This is what im planning on doing. Thanks for not leaving a snarky reply 

Interesting you are more concerned about the form of the information freely given, than the actual information itself.

So be it.

[Don R]

 Be careful with the spark plug threads in the head, they are soft aluminum and easy to cross thread. I like to start the plugs with a piece of hose until I feel them thread in a couple turns and then snug them up with the socket. Often #2 is difficult to get the socket on, especially if it is a thick wall socket.

[Medyo Bastos]

Have you flipped the yellow and blue wires yet?


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[carnivorous chicken]

Have you flipped the yellow and blue wires yet?


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This -- ignition wires might be reversed.

[desertrefugee]

1st thing, is the spark plug socket and get new spark plugs(NGK ONLY)
Get a compression tester from AutoZone ( they have lending tools)

This is what im planning on doing. Thanks for not leaving a snarky reply 

Interesting you are more concerned about the form of the information freely given, than the actual information itself.

So be it.

I was thinking the same thing. 

Spark plugs are "fairly" high up the list of items needing attention during a revival.  (Like #1)

[scottly]

The backfire implies you had spark, but at the wrong time.

[Handlebar]

Get rid of it. The 650 sohc had stator and other electric problems. Goggle it and read all about it.

[fizzlebottom]

Get rid of it. The 650 sohc had stator and other electric problems. Goggle it and read all about it.

Well that seems a drastic non-solution to a non-problem.

[carnivorous chicken]

The backfire implies you had spark, but at the wrong time.

This, although doesn't mean you shouldn't get new plugs or at least check what you've got. Proper plug wrench is an essential tool.