Honda CX500 backfiring

getoutoffirst · L Plate Warrior Joined: 25 Sep 2011 Karma :

Hi Folks

My first posting...................

I have been given a 1980 Honda CX500 that has not been used for sometime but is in reasonable condition for her age. However there are two things that need sorted before I can apply for MOT.

1.It starts on the button but back fires a little for about 30 seconds until it warms up then its fine. New spark plugs have been fitted but not sure what to do next

2. The front brakes are spongy so should I be changing the brake fluid first before doing anything else.

I hope someone can help.

Johno

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

First thing to check is always the diaphragms under the diaphragm shaped plate on the side of the carbs. They split and then cost you a fortune. I can't help more than that because it's about 1,000 years since I owned one. Thankfully.

f.

andys675 · World Chat Champion Joined: 08 Feb 2007 Karma :

advance and retard unit?

mechanic that fixed my mate's said it was a common fault

Tenko · Could Be A Chat Bot Joined: 09 Jul 2011 Karma :

Aye, sounds like carb diaphrams to me as it is an old bike. You could try wrapping them in gas-tape if you can get to them, to see if that makes a difference...

You'll need to change the brake-fluid regardless so may as well to see what effect it has. Just watch you don't shear off the bleed nipples...