Backfires through the carburetors???

[Zombis]

Could really use a jumping off point. I have a 1980 xs650g and would like to get this thing running soon its starting to warm up again here in Redding, CA. Cleaned the carbs, like I really cleaned the carbs. The choke needed new plungers so i replaced them. Replaced the trashed coil with a new one from mikes xs. Ive adjusted the valves and the cam chain adjuster. I was able to ride it yesterday after i replaced the choke tubes, For the first time since i bought it but now its backfiring through the carbs... o yeah. It only ran with full choke yesterday.


Ive got tomorrow off of work and would love to do some wrenching if anyone has any ideas. o yeah the throttle is really slow to come down.

any of you folks have any ideas?

 

[CDNTX650]

full choke...dirty.

 

[Gordon]

You have probably got partialy plugged pilot circut's on the carb's. Popping is either a lean mixture or timing, and on the '80 G, it is not really adjustable. You can use a propane torch without the burner end on it. In stead of the burner end, use a vacuum hose to probe into the area around the rubber intake holder's, and around the throttle shaft area, very common for the 'O' ring's on the shaft to be bad.
The pilot circut is very, very small, and real easy to not get all the crud out of them.

 

[XSLeo]

Carb guide, www.amckayltd.com/carbguide.pdf Lots of info on how to clean and tune your carbs.

 

[twinsarehot]

Yeah, there is a way of cutting off the tops of your "idol adjustment needles". Yours is probably the ultra eco friendly carbs. Get a set of adjustable needles. Also, you may want to check your gas tank for any contaminants. I had the same problem, fixed it with a top end rebuild....

 

[XSLeo]

Cutting off the tops of your " idol adjustment needles" I think idle is the word not idol. And why cut off the idle adjustment needle?

 

[CDNTX650]

you mean popping the caps off that cover them?

 

[Gordon]

I think he's talking about opening the E clip slot to allow some spacer's to raise the needle up. Easier to get the Canadian needle set from Mike's. Either that or the blind plug's that cover the mixture adjustment screw.

 

[gentlemanjim]

One other thought is the slide diaphrams - if not seated correctly or have a hole it will backfire, pop and usually will run up a bit better with the enrichener on.

 

[gggGary]

+3 on the carb guide covering all you need to know. With practice carbs are normally once through and done. First couple of times while you get the hang of it, not so much.
The choke passage in the float bowl is plugged about half the time.

The idle jet found just forward of the main jet is a trouble spot as well. The rubber plugs need to be in place and the jet has a through hole. i.e.; you should be able to see light while looking through the end with the screw driver slot. It is a VERY small hole. you also need to check and clean the air jet in the intake bell.
I like to put a radio shack washer under the e-clip on the taper jet, that seems to clear up the off idle hesitation so common on EPA carbs at least here at 700' MSL.
Did you clean the screens above the float valves and replace those o-rings? Finally set the fuel level which is a bit of a pain on the 80 brass float 34's There is a DIY trick.........