back fires as much as a trucker swears!!

[ratta tatt tatt]

Hey hopefully someone can help

So recently I have replaced/done to my bike - 1977 Honda CB550K:
> Sparkplugs
> Cleaned carbs and replaced old jets with new ones (stock size)
> Oil change
> Put a fuel filter on the line
> New battery

The bike was running fine last year and now it is back firing like the fireworks show on Canada Day! When I start it up it idles and back fires and when I start to ride it back fires and has a little bit of a hesitation off the start(almost like it wants to stall) , but once I get going it runs fine…no back fires and no hesitations…smooth like butter!!

Anyone have any ideas of what I am looking at now? I have had this bike for a few years now and this is the first summer I have had any problems….and its piss’n me off cause I just want to ride!! :'( :'(

 

[Sonreir]

First, verify timing and compression (compression is an extremely unlikely culprit for this, but it's just part of the checklist).

If those are spot on, it's likely you're running lean. I'd pull the carbs again and make sure the correct jets got installed into the correct holes. Make sure no dirt got dislodged during the cleaning process and ended up in the carbs. When you pull all the jets, make sure you can see light through every hole.

 

[lurkmaster2000]

put the old jets back in, why did you change them if the bike was running fine??

if you have a different-than-stock air box/pods, or different-than-stock exhaust then you need different-than-stock jets.

 

[skatetheame]

Some carb rebuild kits come with the wrong sized jets even if they are marked the same size as the stock ones.

 

[Swapmeet Louie]

ya, its leaning out for one reason or another. Did you mes with yer pilot screw..? but none the less, like said, it's running lean. (if timing is spot on. but you didnt say you changed that)

 

[ratta tatt tatt]

I didn't mess with the pilot screw at all.......and the old stock jets looked like they were about to fall apart! if you say that some of the new jets that claim to be the same size are not really the same size as the originals then maybe/hopefully that is the problem.......

thanks for all the info guys....hopefully I get this problem licked and have no more :-\

 

[Swapmeet Louie]

was it a Keyster kit?

 

[crazypj]

plug caps wrong
you probably did 1234 when it should be 1/4 &2/3

 

[Swapmeet Louie]

^^^ I'll bet....