Honda CB500F 1972 wont start


Active Member
Hey guys,

Since being away on an overseas trip i havent been able to get my CB500 to start up. Its been idle for perhaps 15-20 weeks now.

The battery is fully charged, the start motor is working fine, i've changed the spark plugs and put new fuel in the tank but it wont catch.

I'm a bit lost as to my next steps to take, i am a novice. But could you guys please let me know what else i should be looking at in order of importance.\

Thank you in advance.
Hey man, thats a bummer.

My guess would be the float bowls are full of gunk. Gasoline deteriorates over time and becomes a sort of glue, blocking passages in the carbs. Take of the carb rack, clean the bowls (one by one, you can not interchange parts from one carb to another) and try again.

I've read stories about seafoam and such to work but somebody from USA has to chime in here as we do not have that stuff over in the Netherlands.

You could also try to use some starterpilot. Might just give er some punch to start and when the gas flows again, some junk will flush out.
Drain your float bowls first of all to get some fresh gas in there. If that doesn't work then you'll have to rip the carbs off like Bertjan has said.
I would suggest checking to see if you have spark at the sparkplugs before ripping the carbs apart. Could be an electrical problem, ie., the coils, points
As above with the references to the carb, check the float valve needles are not stuck. They can get gummed up from the old fuel.

I would also drain the fuel tank in case water has condensed in there.

Also check you haven't done something stupid, like turn the petcock off and forgotten it.
Hey guys!

Thank you for all of your replies.

I have ordered a series of carb rebuild kits, and have so far managed to remove the carb assembly from the bike and separate the carbs. Quite a mission for a man of my experience, but one i thoroughly enjoyed. Looking forward to the real fun of dismantling and rebuilding the carbs, wish me luck!

Until the carb kits turn up i have to put this on hold, being in New Zealand makes parts hard to find at time.

Just a side note, the bike wouldn't start with the petcock in either the on or reserve selections.

I am considering removing the OEM airbox while i have the carbs off and install a series of pod filters, like the ones on Is there any major issues i should be aware of? Will it lead to any chance in performance? Does it require more upkeep? etc etc

Thanks again guys!
Pods will require a lot of tuning work, rejetting, changing needle positions etc. They won't give that big of performance gain unless you also play with exhaust etc. I would leave the stock airbox on if you are fairly new to bikes until you get it running right, then you can tackle pods as you will know how the bike should run, before adding the pods to the equation.
Did you check to see if you have spark at the spark plugs??????

Hey glen wood sorry for the late reply, yeah seems to be sparking fine.

Still waiting on the carburetor kits hopefully that fixes it
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