Carb repair

Murgatroid

Murgatroid

Junior member
Location
Nevada City and Sunnyvale, CA
So the left (cyl1?) carb on my '77 3CL has started to spew fuel out the overflow. I removed the carb bottom to look at the float and needle valve. What I've found is that one of the perches for the float pivot pin has broken and is currently being held in place by what looks like masking tape. Yes, really.  Masking tape.

Is there an adhesive that can be used that is impervious to gas (with 10% ethanol!)?  Should I look for a replacement carb body?  Any other options?  If anyone has a spare carb body to sell, let me know!

By the way, my DMC went south and it was out of warranty.  Uwe Witt replaced it at no cost.  I can't speak highly enough of Motowitt! 

Steve
 
Steve, if you Google "aluminium solder" you should be able to find somebody local selling one of the products in this category. It comes in a rod (like a welding rod) and needs a LOT more heat than electrical solder (one of those little butane brazing torches is real handy if you don't have oxy-acetylene). You'll need to clamp the bit you're soldering well, and you'll probably need to file a bit of a bevel around the edges of the bit you're "soldering", and you may need to use a Dremel a bit after everything cools off to remove excess metal.
But I don't know of any adhesive that will work in the soup of hydrocarbons that is petrol. A laser welder could also work, you might be lucky and have somebody who can laser weld near you. I don't.
Or you could wait until somebody on this forum offers you a carburetor for a fair price. Dozens of us have replaced Dellortos with Mikunis, somebody must have a set of Dellortos they're ready to split up for some reason.

Ken
 
You will melt it trying to solder it, carbs are made from Mazac which is a very hot short material. Means it goes from the solid everything looks fine stage to the melted mess on the bench stage within a few degrees.
I can sort you out with a good body, back in the workshop on the 28th, drop me a line then.


Keith.
 
Keith, didn't know that about carbs, good to know. I used aluminium solder to seal a non-structural crack in my top crankcase (DPO dropped 630 chain). Lot of hassle getting it hot enough but not too hot (infrared thermometers are great!), but it does seem to have worked.
I Googled "gasoline-proof adhesive" and came up with Master-Bond EP41S-1HT (http://www.masterbond.com/tds/ep41s-1ht) which looks like it would work, also probably good for holed crankcases, leaky petrol tanks. Maybe? Anyone ever tried it, or something like it?
From experience I can definitely say that the epoxy that Caswell's uses for tank liners does seem to be totally resistant (to US fuels anyway), so it can be done. But I suspect it's still a bit flexible when cured, probably not a good choice for carburetor repair.

Ken
 
Epoxy resin is fuel resistant. A kneadable putty would make it easy to form the shape. There's bugger-all load on it in service, so it should work OK if you can get a good key to the parent metal. Worth a try at least.

Cam
 
JB Weld would be another candidate to use, if it is capable of surviving inside a combustion chamber then a float support repair would be no issue

 
I like Keith's suggestion of being able to supply a 'good body', at my age mine's totally buggered, arthritis, collapsed discs, etc etc........................ :D :D
 
Second for the JB weld used it for heaps of repairs back in the day and still swear by it. Also as an added bonus you wouldn't have to worry about catchin fire using a naked flame torch around Petrol. Just make sure the area is really clean and if you can clamp together till it sets you should be good to go.
 
Yeah, I did some searching trying to find just where you can buy the Masterbond stuff from, SOL so far. But I would like to have some in my repair stuff box, if it's as half as good as the blurb says it should be some pretty useful stuff.

Ken.
 
Have had these support posts sucessfully laser-welded, good as new.  Have also used "Lumiweld" to repair an Amal carb float bowl, bit tricky, but worked out well in the end.

piet
 
Piet's laser welding guy is good.

Inside:
vz3h.jpg


Outside:
mmw1.jpg

 
Aluminium solder - Lumiweld, Durafix, or whatever name it goes by, is simply die-cast metal. Same stuff that Dinky toys are made from, which is usually an alloy of zinc, aluminium and copper. Pretty much the same ingredients as Mazak, but possibly in different quantities.

I've found it a bit tricky to use becsuse you need to get throught the oxide coating on the aluminium to make a good bond. Aluminium oxide forms immediately bare aluminium is exposed to air, so you need to clean the joint surfaces inside the weld pool while you are welding. Not an easy thing to do.

Cam
 
Just called Masterbond to see how to buy their magical adhesive stuff. No wonder they don't list distributors or dealers. They make everything to order and sell only to industrial users. They reckon 8 ounces (~250g) of the fuel resistant stuff would cost about $700.
I didn't order any. Did think about trying to order a sample, though, they must be able to do that.
They suggested Devcon and Cotronics as possible suppliers but neither one makes a specifically petrol-resistant epoxy, although they both have stuff that would be great for Zamac (apparently it's Mazac in the US, Zamak in Germany), just not carburetors.

Ken
 
by far the easiest repair is to change out the carby body itself, they are as cheap as a Boxing Day sale, I have dozens of spare Dellorto carb bodies here
Keith would be the same, awash with Dellorto carbies
stuff the repair work, why bother when a replacement is so cheap and easy to get

 
redax5 said:
by far the easiest repair is to change out the carby body itself, they are as cheap as a Boxing Day sale, I have dozens of spare Dellorto carb bodies here
Keith would be the same, awash with Dellorto carbies
stuff the repair work, why bother when a replacement is so cheap and easy to get
Click to expand...

That's a reasonable approach.

If part of the original body is broken it may be due to a manufacturing flaw. Perhaps there are others there as yet undiscovered.

bazzee
 
Yup, I agree.  Just waiting to hear from someone with a spare carb body and a price.  Anyone in the US?  I'll consider you furriners, too.

Steve

redax5 said:
by far the easiest repair is to change out the carby body itself, they are as cheap as a Boxing Day sale, I have dozens of spare Dellorto carb bodies here
Keith would be the same, awash with Dellorto carbies
stuff the repair work, why bother when a replacement is so cheap and easy to get
Click to expand...
 
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