Vac Line for #2 Carb

[RichV]

I have a problem that I couldn't find an answer to in the forums so if it's there, please just provide the link. I'm working on a 81 XS1100 Special.

While cleaning the carbs during a rebuild, I found that one of the posts for the float was broken. I have a spare set of carbs so I just opened up the #2 spare and found that it was broken as well and jury rigged. Carb #2's body is the same as the other carbs (almost) so I'm looking to swap one in I know is undamaged. The problem is that #2 has the vac line for the ignition advance on the output side.

It appears to be a pressure fit copper tube and on the other carbs, the hole is plugged. So here are my questions.

1. If I drill out the plug, how deep should I go? I can measure it but it may not be accurate.
2. Is there an easier way to handle this?
3. Is this post being broken a common problem?

Thanks again for all the help you guys have given me so far.

[DGXSER]

I can only answer one of your questions, the broken float post is not an uncommon problem. Many ways have been devised to repair these.

HERE is a thread on a method or two I used. With your having two with broken post, the first method may work well for you.

[natemoen]

In your other post you say that it is #3 that had the broken post.

You could put a #1 carb in place of #3.

#1 and #3 can be interchanged and the #2 and #4 an interchange. Some work might be needed depending on which ones are moving where.

[GLoweVA]

Rich, if you do plan on drilling a different (1,3 or 4) carb body to put the vac advance port in, be careful and measure the hole size.
That port is very small to meter the vacuum to the advance mech.
John (Nightengale) was thinking about doing this to his FJ carbs that he has on his XS11, but hasn't yet. (probably out of fear of screwing it up)
His bike runs fine without the advance, but I think his mileage suffers a little.

The thought is: you use a bit the size of the tube, and go just deep enough to fit the tube in, then a really small bit for the metering hole thru to the throat of the carb.

You may be better off repairing the float post. There are som engenious ideas on different fixes here on this site. I like the threaded type fixes. They seem to hold up well.

[natemoen]

The thought is: you use a bit the size of the tube, and go just deep enough to fit the tube in, then a really small bit for the metering hole thru to the throat of the carb.

I would suggest doing it the other way around. Drill the metering hole first. That way you have the thickness of the metal first and then you can set a depth for the larger hole.

[BA80]

The #2 carb is the only one that is extremely difficult to swap with another. 1,3,&4 can be swapped around simply by changing the butterfly linkage. It's almost impossible to drill a #4 carb to swap out with a #2. You have to drill it pretty much EXACTLY in the right spot to get it right.

What year bike do you have? I don't see it in your signature.

[RichV]

Sorry about the confusion in the previous post, I got the carbs backwards on the bench when I made the post. It's #2.

I just spent some time looking over the carb body more closely and there are several little differences. It would be MUCH easier to just fix the post and move on. After all, it's just the post for the float and not a high stress item.

Thanks again for the help.

[skids]

I had a broken post in one of my three running xs11's. (maybe I still do). With mine, although the goal post was broken, the axle was secured from one side, the carb worked perfectly. I think one the side was broken right at the hole bottom and the axle was touching a hole remnant.

Concerning the vacuum advance to the carb, the hole is small to help prevent pressure pulsing. I would think that if you drilled a small hole (but larger than the OEM hole) all the way through the plug, the resistance might end-up being the same as the OEM hole. I know you are probably worried using the tiny drill bit that you would need if you bored through into the ventouri. Does this make sense to you? It does to me.