Re: cb750 popping/backfiring

Posted by trapper on May 13, 2013; 4:49pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/cb750-popping-backfiring-tp4040698p4040709.html

First things I would look at are your plugs. Pull each one and notice the state of them. Do they look like the cylinder is running to rich/lean? Compare them to pics in your manuals or online if you don't know how to tell. Simple adjustment. Give 'em a good cleaning or replacement based on that. Second of course would be timing. And, if you cleaned the carbs, I'm assuming you removed them and pulled them apart? Did you sync them after? If not, might be something you want to look in to even if it's not your problem.  I had a simple popping on my 81 C, a quick plug cleaning and once I got the carbs balancedm, it went away.
Syncing the carbs can be a pain if you don't know what you're doing but, once you get the hang of it, it's not so bad. There are hundreds of youtube videos on how to do this. Actually I believe there is a link in this forum somewhere that has some great info on it. You will need some gauges for this. If you can get the mercury ones I would shoot for that but, with some practice the air ones do work.

Hope some of that helps.

*Edit... Also, when looking at your plugs, check the gap. The correct gap will be in the manual. Do you understand how to adjust fuel/air mixture?