I need some help

[Mattneedshelp]

I got my first bike and its a 82 honda CB750, I started it when i first got it and then the battery wouldnt keep a charge.  I bought a new battery and then i tried to start it and it wouldnt idle and then it backfired really big and now it only turns over.  Of my knowledge the sparkplugs were just replaced. does anyone have any ideas?

[blackhawkrider]

how long before you got it did it sit? If it has been a while its probably time to clean carbs out.

[Mattneedshelp]

It sat for about 2 years becuase the previous owner only rode it four times then sat since last year.  It started up when i went to see it but it sounded like they were getting clogged a little.  now when i started it up it backfired really big. I hope its not a very serious problem

[shabbabear]

if you bought a new battery and it won't keep a charge then you probably have a charging problem...easy check for that...once you get it running....disconnect your brake light leads at the right h'bar and put a multi-meter on the leads with your meter at DC reading and rev the bike....volts should go to 14.2 dc max or always over 12v. that will also possibly explain that when you do get it running why it backfires...bad charging system means poor current to your coils which means poor spark which means unburnt gas that ignites in the heads or collector thus the backfire. other guys are right, start with complete carb clean..i know its money but a good dealer will have one of the ultrasonic machines like we use at our dealership and it will do 100 times better than you will ever get at home on your workbench with the old carb cleaner and toothbrush method...the best ultrasonic machines blast it with the equivalent of 3000 psi but with sound waves so no damage to delicate parts...so 1)do carbs 2) check spark with new plugs and check coil output 3) clean airbox and filter 4) have fresh good fuel and a cleaned petcock...that should get it ....except for the carbs it can all be done in a couple hours...note !!!!...if you take your carbs in to be cleaned professionally then tell them to throw in your petcock after you disassemble it they should do it for free like we do...good luck friend....shabbabear  

[Mattneedshelp]

Thanks that helps alot.  Do you know any good machanics in Cincinnati? I am going to get the carbs cleaned so hopefully that works thanks for your help.

[blackhawkrider]

a basic clean isn't hard. If it runs, you might get by by putting some carb cleaner down the fuel line and into the float bowls. I like yamaha brand carb cleaner because it is meant to be used this way. Just follow the instructions on the bottle. If your bike has the autopetcock on it you will need to by pass it. Also drain the fuel out of the bowls before putting the cleaner down the fuel line. If that doesn't work you will have to take the carbs off and do a more extensive clean. Also balancing carbs is a must on these bikes makes a world of difference.