1978 Honda CB 400Twin - Rough Idling and Popping/Cracking Sound

[ChrisMartucci]

I was wondering if you can help me. This is what happened when I started my bike this morning...

- Idles rough
- Backfiring
- Smoke coming from tail pipes
- Clicking noise coming from engine block
- Revs really high then shuts off
- It won't stay on if I'm not turning the throttle at least a little bit, as soon as I let it go it shuts off.
- And even with the trottle on - the engine always cuts off and there is a pretty bad "popping" sound in the tail pipes.

Any idea what could be causing this? Or how I can temp fix to it?

 

[Freestyle72]

is your exhaust on tight and does it have any holes or leaks?

 

[soto]

Also check if any leaks between airbox/carb/engine. There might be a loose connection there somewhere.

 

[handlegrip]

Is there any water in your ignition modual? Stuff like that does not happen over nite, there is another element. A wet ignition could do that.

 

[Stewart]

these bikes have bad pick up coils for the age of the bike, but you might want to clean the carbs for bad gas.

 

[Spiider]

These bikes usually/frequently require a good carb clean...and that doesn't come from a spray bottle.
It comes from taking them off and doing it properly.

Learn online if you don't know how.

Also, avoid ethanol gas like the plague.

After that's all done, perform a 3000km tuneup...oil, air filter, check plugs, adjust timing, carb sync etc.