Fun with Carbs

[RichV]

I just wanted to show everyone something I found when I tore down the carbs. I was having problems with the #3/4 cylinders not firing properly so I felt a good cleaning was in order. What I discovered was amazing.

Carb #3 had a broken float mount and #4 was using a nail as the float pin. It was working but had jammed. The three photos show the carbs, the broken post on #3 and nail for #4 (I actually held it over #1 by mistake). As for #3, the mount was repaired with Bondo which didn't hold. One of the jets had also fallen out and another was stripped. All in #3.

I have a spare carb for that position which will work after extensive cleaning. I'll also brake the mounts apart so I can clean the carb bodies better and replace the broken one.

Here are the photos...

[skids]

Yeah, you never know for sure unless you tear it apart (unless you are the original owner).

[DGXSER]

Carbs are like a box of chocolates, you never know what you're going to get.

I did a repair of the float post before. Best method was taking a float post out of a scrapped carb body. Next best was to use a piece of aluminum rod that I cut down, threaded and then drilled and tapped a hole in the remaining float post on the body. Trimmed the sides and installed it, marked it in place, then drilled the float pin hole.

[RichV]

I'm at an advantage here that I have spare parts to work with. I purchased a flood bike and have been taking things off of it to repair this bike. It was totally stock with no modifications so I was able to fix most of the mods done to this bike.

So I have a good one sitting in the tank getting cleaned from the flood bike. I also have two extra chrome caps for #2 and #3.

These are relatively simple carbs with very little adjusting to be done so cleaning them up and syncing the throttles should make it run like a top.

[DGXSER]

Having spare parts does make it much simpler!

Yes, it will help to bench synch and then of course perform a running synch and tune.

[RichV]

First, I was really talking about Carb #2. Got them backwards.

Second, the spare I have is also damaged so I need to use one of the other carb bodies to replace #2. The problem is that #2 has a vac line on the output side which is a copper tube fit into a hole that is plugged on the other carbs.

I guess I need to drill out the plug on the replacement and tube.

[RichV]

Well there are differences between the #2 carb and the rest beyond simply drilling a hole. I read some of the fixes posted HERE for the float post problem and did the following.

1. Cleaned up all the bondo.
2. Drilled a hole in the base of the post using my drill press. To match a SS bolt I had on hand.
3. Threaded the hole to match the bolt.
4. Cut off the head of the bolt and filed down the 2/3rds of the threads on half the remaining bolt.
5. Threaded the modified bolt into the base and secured with threadlock (deep inside) and tightened.
6. Drilled a hole in the bottom of the broken off part of the post slightly smaller that the hole in the base (it may be the same, I can't remember).
7. Put a strong, gas resistant adhesive in the hole deep.
8. Pressed the top part onto the de-threaded bolt now in the base.

The solution relies on a pressure fit to hold it in place. The glue was just to add a little more holding power (not much). The broken off part fit almost perfectly on top of the base. I just had to tap it a bit on one side to provide the proper clearance for the float.

The main advantage is that bolt holds the part back onto the base like resetting a broken bone. It took me about 30 minutes to do everything.

I would have posted a photo of the final fix but photobucket is down.

[DGXSER]

The main advantage is that bolt holds the part back onto the base like resetting a broken bone. It took me about 30 minutes to do everything.

Kind of how I came up with the idea. A titanium rod holds my tibia together.

[RichV]

Kind of how I came up with the idea. A titanium rod holds my tibia together.

Your post was definitely the inspiration for how I approached it. Thanks for posting it.

[RichV]

Here's the photo of the final fix. I was able to put the float back on with proper clearance on the sides. As you can see, the break was at an angle so drilling the holes was a harder than normal. Luckly I have a drill press. Even so, it's a slight bit off but who cares. You can see the little divot I cut out of the righthand post with the cutoff when I removed the top of the post I added to the left one. Anyway, I may seal the crack but I'm not hyper about it.

[RichV]

All done. I could only work on these a little bit at a time. I also cleaned all the rust and corrosion. I used the chrome caps from the spare set to make all four chrome.

Next step is to test them on the bike. Maybe today.

[DGXSER]

Nice work on the repair! That is a challenging arrangement for sure with the angle break. I would not worry about the slight offset. If you look at the factory arrangement, it is not THAT close of a tolerance set up to start with.

Those carbs look clean enough to eat off of, should be ready for miles of smiles!

[RichV]

Nice work on the repair! That is a challenging arrangement for sure with the angle break. I would not worry about the slight offset. If you look at the factory arrangement, it is not THAT close of a tolerance set up to start with.

Those carbs look clean enough to eat off of, should be ready for miles of smiles!

The float is moving fine and the repair is solid (I hope). Anyway, it didn't react to the installation of the pin.

The reason it took so long me to complete this is because of the cleaning. While I didn't do the "Triple Cleaning" suggested in posts, I did soak the parts for extended period, brushed them out and ended with a second dunk for a few minutes to "rinse".

Final note, I don't like rust on carb parts. Looks messy. However, I don't usually shine the aluminum parts so the slight surface discoloration still exists. You can make them look too shinny and they appear out of place with the rest of the bike.

I still need to bench tune and re-install. I have only one vac gauge so that will be challenging but doable.

[GLoweVA]

I still need to bench tune and re-install. I have only one vac gauge so that will be challenging but doable.

Rich, get one of those 4 way aquarium air valves (for the air pumps), then you can hook up all 4 vac ports on the carbs and then use the ganged valve bank to select which port you're sampling from for the vacuum sync.



That pic is from the tech tip:
http://www.xs11.com/forum/showthread.php?t=986

[RichV]

Here are the carbs re-installed on the bike (below). Started up right away and ran fine. I only had to adjust #1 a little to bring the vacuum in line. Close enough anyway for the next step which is to move everything to the painted frame.

I built the device GloweVA suggested and it worked great. Much better than a direct connect and the valves made it easy to move from cylinder to cylinder.