Crack in Take-off tube...

[Janicki]

So I posted awhile back about the 79' XS 650 I salvaged from my mothers garage. I have been going through the motions laid out on the forums. I just pulled the carburetors out and it looks like whoever had them apart last tried to use a gasket maker over the old gasket... Well it deteriorated and the remains were floating around in the bowl. I figured I found my problem for the backfire on the deceleration on my left side. After giving everything a once/twice over I through some new gaskets in and put it back together and synced them. Well... now I have backfire on both sides at deceleration and Idle. I pulled the carburetors out again and gave it another once over.

This time I noticed there is a 2 mm hairline crack running vertically from the tip of the take-off tube. I have been searching the carburetor guide and all over the rest of the web for more information on this piece.

Could this be causing the issue i'm having?

Is it serviceable or is this carburetor basically junk?

 

[5twins]

You'll have to be a little more specific with your description about that "take-off" tube, such as where exactly it's located. A pic would probably be best. The only take-off tube I know of in the '78-'79 carbs is the one for the choke. That shouldn't affect normal running, only choke use, and then only maybe.

It sounds more like your idle circuits are still blocked or partially blocked or it could be as simple as having the mix screws set wrong. The mix screw spec for that carb set is 2.25 turns out but many like closer to 2.5. If you're running them around 1.5 turns out, that would cause popping like you're seeing.

 

[Janicki]

I have adjusted both the mixing screws to 2.25 and even played with settings at 1.75, 2.5 and 3.

I've attached the image from the carburetor guide which I used to identify the piece in question.

 

[5twins]

That's the choke take-off or feed tube. It shouldn't have any effect during normal running as it's not in use. As long as the bike is starting easily when cold and using the choke, I would say that cracked tube isn't hurting anything.

The popping is usually caused by a lean condition. What condition are your manifolds in? If they're old and cracked, they may be sucking air. Removing and installing the carbs can make them worse (you had popping on one side, now you have it on both).

 

[Janicki]

Thanks 5twins, I'll check them out after work today. I really want this bike running smooth for the slimy crud run (http://www.slimeycrudrun.com/) this Sunday and I thought it was for sure a no go when I found that crack.