75/6 Carb damage question

I have a new-to-me 1974 R75/6 and I'm currently in the process of taking it apart to do the rear main seal.

Took the CV 64/32 carbs off this weekend- I will be cleaning and re-building them as well- and finally got a good look at them now that they're off the bike.
This is what I found:



the brass tube, that comes down from the main body, below the throttle assembly, into the bowl- is split
what the heck?!?

so what do I do about this? send it to Bing to repair?
And how the heck did somebody do that to it in the first place?

thanks for the help-
Kat

katcon85 said:

I have a new-to-me 1974 R75/6 and I'm currently in the process of taking it apart to do the rear main seal.

Took the CV 64/32 carbs off this weekend- I will be cleaning and re-building them as well- and finally got a good look at them now that they're off the bike.
This is what I found:

View attachment 42111

the brass tube, that comes down from the main body, below the throttle assembly, into the bowl- is split
what the heck?!?

so what do I do about this? send it to Bing to repair?
And how the heck did somebody do that to it in the first place?

thanks for the help-
Kat

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Since the tube is brass, I'd try to close the split with solder.

Either solder, or go to your local hardware store or even hobby shop and obtain a piece of brass tubing that will fit over the existing tube and solder that in place.

MANICMECHANIC said:

Either solder, or go to your local hardware store or even hobby shop and obtain a piece of brass tubing that will fit over the existing tube and solder that in place.

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Try a store that sells remote control airplanes. Do they ever have a great supply of stuff to help repair most anything!

Another easy fix could be JB Weld - sold at most any automotive supply store.

BTW did this crack result in gas leaking down onto your foot?

Water froze in the float bowl, thats how it split.

I was wondering about the "how?", that makes sense.

BTW, that is the tube that feeds fuel to the enricher.

How "full" does the well get that this brass tube sticks into? Does it really need to be fixed or could it still draw fuel to the enrichener as it exists now?

well, it just sticks down into the bowl, and draws up from there.
I'm not sure if the top of the split- it's actually split in 4- is above the fuel level, but if it is, I'm thinking it would draw in air, and not work.
But if it goes to the enricher- does that mean that it's just used during choke?

katcon85 said:

well, it just sticks down into the bowl, and draws up from there.
I'm not sure if the top of the split- it's actually split in 4- is above the fuel level, but if it is, I'm thinking it would draw in air, and not work.
But if it goes to the enricher- does that mean that it's just used during choke?

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After looking at it again, I would purchase some small brass tubing at your local R/C Airplane store (a huge hardware store like near me, also) that has an ID the same as the OD of your split tube. Press it on, and use some rosin core solder with some good flux, and solder. After cleaning, soldering should only take around 5 minutes.

Like a straw with a hole in it in a soda drink, if the crack goes up to above the float bowl fluid level, it will suck air instead of fuel.

The cracks could also be soldered without any separate tubing, but it would need to be cleaned thoroughly (small wire brushing) so the solder can bond to inside edges of the cracks. Use good flux to help clean. After soldering, be sure to clean out so that the tube is not blocked with solder.

katcon85 said:

well, it just sticks down into the bowl, and draws up from there.
I'm not sure if the top of the split- it's actually split in 4- is above the fuel level, but if it is, I'm thinking it would draw in air, and not work.
But if it goes to the enricher- does that mean that it's just used during choke?

Click to expand...

That is correct. When the enricher is in the off position, that circuit is not in play.

There is a jet in the bottom of the "well". This is often a cause for difficult cold starting if that jet gets plugged up. The well fills to the level of fuel in the float bowl.

split tube on enrichener pickup

The enrichener has a jet at the bottom of the well, as noted by someone else, the jet must be clean/open.
The enrichener at the carburetor has its own 'jets' as part of the rotating disc, thus, how you get more or less enrichening by moving the choke lever.
The fuel in the fuel bowl, engine off or enrichener not in use, fills the enrichener well to the same height as the rest of the float bowl. The pickup tube, in this case split pickup tube, dips into the well, and when the enrichener (choke) is used, fuel is sucked-up by vacuum action into the enrichener disc and body area, which distributes it in the amount the position of the disc is set for.

Here is why the jet and tube must be in good condition (sweat solder with a thin tube over the original, WILL work adequately enough although there is an effect from the VOLUME of the added tube)...or, solder the crack.

When the engine has the choke on, especially full choke, the well is drained quickly by the enrichener, which is a crude carburetor in itself.
After maybe 10 seconds or bit more, the JET at the bottom of the well is the only thing supplying fuel to the enrichener...and the amount is controlled by the jet size. Think about this limiting of the fuel for a bit.

snowbum

enrichener pickup tube

The flying fingers hit send too quickly.

The enrichener lever, when on the bars (later models, that is, after the seventies) is marked as a "choke". It isn't really a choke, but a control for a separate very crude enrichening carburetor function, located on the side of the carburetor. It is, in a sense, a calibrated porting arrangement for nearly raw fuel, in small volume, to be introduced into the carburetor. Early carburetors such as those with model numbers ending in /1 through /12, had quite different internal passageways, and even fewer idling and enrichening ports. Not going to get into those at this time....suffice to say that some of the old carburetors were not as stable, harder to adjust, and some had some real problems with unstable running, particularly at idle and just off-idle. The /1, /2, and the R75 with its /3 and /4, were particularly egregious. Not all exhibited the problems. Article is on my website dealing specifically with the /3/4.

One of the things not known widely, is that the BOWL GASKET must be in good condition, for the enrichener to work properly on ALL the Bing CV carbs. The gasket around the bowl well must be intact, NO split/crack in the gasket. That is because it is vacuum that is in the vertical tube, that raises the fuel into the thin tube. The area on top of the fuel in the well is not exactly at atmospheric pressure during operation and it VARIES. The MAIN BOWL fuel level is at atmospheric due to venting; which is NOT applied to the top of the enrichener well. Thus, a bad gasket will be just one other thing that can cause the enrichener to not work correctly.

The enrichener parts are NOT identical for left and right carburetors. DO NOT mix up parts when overhauling carburetors.

SOME enrichener SHAFTS had the punch prick mark WRONGLY DONE AT THE FACTORY. This can drive you crazy if you do not know about it, because it is that punch prick mark that you are supposed to use to set the parts in the correct position.
My website has photos of the correct, and incorrect way to assemble the parts. I have seen wrong punch prick marks on bikes into the EIGHTIES!

The following is contrary to owners booklets: The correct way to start a cold engine is full choke setting, crank the engine while manipulating the throttle between off and just barely open a bit, and as soon as the engine starts, try backing off the choke setting a bit, particularly if the choking effect is causing the engine to run roughly.... continuing backing off a bit at a time until the engine has been running for awhile....and the choke is fully off. The carburetors vary over the years, especially the early carbs in the /5 and early /6 era, and how much and for how long the choke is needed varies considerably. The right amount of choke is the minimum needed to have the engine run smoothly. Some bikes can have the choke fully turned off rather quickly. The adjustment of the idle mixture screw has quite an effect on how the choke works during initial start and warmup. The idle mixture screw should be properly adjusted, and the balance and the final rpm, until all are perfect. The final adjustment can NOT be made until the bike is ridden at least 10 miles.

Another factor, is the idle rpm that the carbs were tuned-for after a full warmup. It is NOT good for the engine, especially a worn engine, to be idled below ~850, and I recommend about 1000 for all Airheads. It would take a couple of paragraphs to get into all the reasons, so I won't at this time.
snowbum

THANKS SO MUCH for sharing your knowledge, experience, common sense, and realities of how these machines REALLY work. Could say so much more about the service that you provide to us all..........God bless......Dennis

I had the same problem. My brother fixed it for me in a barter situation.. but I had also contacted Bing and they said, "We offer an in shop repair @ $28.00 + return post." Not a bad price, really.

How these things work as described above is interesting, but it seems to me that some are making this into a huge problem. I still could be a problem, but fixing the tube by soldering either with another small tube surrounding it, or without, I would venture a bet, would be all that is needed. About 15 minutes of your time would be all that it would take to find out. And...I bet it would work as good as it is supposed to and you wouldn't know any difference. Any fix would be better than it is now.

If it doesn't work, then think about the more expensive fix. Why turn a simple problem into a huge one?

Thanks Snowbum for the technical info on the pickup tube. (and for ALL the info on your site which helps tremendously)
FYI these carbs are 64/32/ 9 & 10 - so they are very early /6 carbs. Bing book actually attributes them to /5.

I called Bing yesterday and they will replace the brass tube for $50 if I send it in. I think I will go with this, as I don't trust myself to solder repair the tube w/o f-ing it up worse or soldering it shut. And I have plenty of other stuff to work on now (rear main seal, push rod tube seals, drive shaft leak). I'm still a beginning wrench, and replacing 'o' rings is about as far as I want to go into the depths of carburetor repair!

thanks all
Kat

A very wise decision Bud...........Besides the saying, "if it ain't broke, don't fix it"............."Don't jump in the water if you don't know how deep it is" really does apply..................What has always bothered me about your situation that you describe is the lack of knowledge on if the bike even runs and how good...........Besides the split in the tube is the bend or off-center situation as it sits in the hole...........Would be good to know if the tube is even open for flow.
For my money, lol......and it is yours......you are really doing the best thing.............God bless......Dennis

katcon85 said:

I calleded Bing yesterday and they will replace the brass tube for $50 if I send it in.

thanks all
Kat

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Dennis D' has given you good advice here. However, if you have decided to send the carburetor to them, (Bing) you have NOTHING TO LOSE, other than a few days lag time, to give the solder job a try.

I was once scared to try to fix my own bikes. After a huge bill from an independent shop, decided that the worst I could do was have to take a bike (or part) somewhere after I screwed up. That was 20 years ago.

katcon85 said:

these carbs are 64/32/ 9 & 10 - so they are very early /6 carbs. Bing book actually attributes them to /5.

I called Bing yesterday and they will replace the brass tube for $50 if I send it in.

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My problem was on the same set of carbs for the same year/model bike. It was only in July that Bing told me they'd do it for $28, so I can't imagine why the price increased 78%. Maybe ask them for a better deal.

James.A said:

Dennis D' has given you good advice here. However, if you have decided to send the carburetor to them, (Bing) you have NOTHING TO LOSE, other than a few days lag time, to give the solder job a try.

I was once scared to try to fix my own bikes. After a huge bill from an independent shop, decided that the worst I could do was have to take a bike (or part) somewhere after I screwed up. That was 20 years ago.

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