Carb body repair

microflitedude wrote:JB Weld?

Matt,

In my experience JB weld and plastic do not play nicely together. It doesn't want to adhere well. JB weld is fuel resistant though as I have used it to repair pin holes in steel gas tanks.

cribbs74 wrote:

microflitedude wrote:JB Weld?

Matt,

In my experience JB weld and plastic do not play nicely together. It doesn't want to adhere well. JB weld is fuel resistant though as I have used it to repair pin holes in steel gas tanks.

Hmm.. We once used it to repair a broken plastic governor/throttle arm on a gasoline Go Kart. Very stressed part, held up great. (pedal punches and offroading) Maybe some light sanding would help it bond.

microflitedude wrote:

cribbs74 wrote:

microflitedude wrote:JB Weld?

Matt,

In my experience JB weld and plastic do not play nicely together. It doesn't want to adhere well. JB weld is fuel resistant though as I have used it to repair pin holes in steel gas tanks.

Hmm.. We once used it to repair a broken plastic governor/throttle arm on a gasoline Go Kart. Very stressed part, held up great. (pedal punches and offroading) Maybe some light sanding would help it bond.

It's worth a shot, can't break it any further. I can make it uglier!

Once I got a new Killer Bee backplate with a loose spraybar that would spin when I turned the needle. It had never been run, so there was no chance of oil on it. I pulled it out and put JB Weld on both parts and pressed it together. A week later I built an engine with it and flew it a couple of times. When I was cleaning it, I checked and the spraybar had come loose again. Maybe I should have roughed up the plastic some before I pressed it back together.

Maybe you could use a plastic welding kit to seal it up. http://www.eastwood.com/steinel-heat-gun-how-to-plastic-weld-plastic-welding-tool

Good to know Rusty,

This thing is covered in 40yr old castor so I will have to clean in first. Roughing it up inside the split will be hard. Plastic welding kit is a good suggestion but it would cost me more than a new carb body.

Personally, and I have done similar repairs, I'd use the thinnest grade of Cyano,(Superglue) it penetrates right into the crack and I've never had a repair crack again. Use a needle-type applicator, and try not to get to much of the cyano on the outside, it can attack some plastics, I used it once to fix an acetate cockpit canopy and the fumes turned the acetate white.

For future reference you need 'foam safe' cyano Wilf, it doesn't whiten.


FMK/5Star do allsorts of cyano and plastic fixing stuff including those microwavable plastic
pellets, which thinking about it may be the solution to the above.
J

I dont know how well it would work with Cox plastic, but in the past I have used a pencil type soldering iron and basically hot smeared a leaking plastic crack shut on a nitro fuel tank.

John Goddard wrote:For future reference you need 'foam safe' cyano Wilf, it doesn't whiten.


FMK/5Star do allsorts of cyano and plastic fixing stuff including those microwavable plastic
pellets, which thinking about it may be the solution to the above.
J

Right, thanks John, I'll bear that in mind next time I need it.

Wilf

I'll try the Foam safe CA first as I have some laying around. Should that fail then I can try the other options suggested. Or I can buy a new one................Thanks all!

How about an aluminum ring turned and then slip fit over the carb throat. It would be cut to fit. It can then be JB welded in place.

Jason

Jason_WI wrote:How about an aluminum ring turned and then slip fit over the carb throat. It would be cut to fit. It can then be JB welded in place.

Jason

Another swell idea! Actually I think I have seen that somewhere. Can't remember

Care to turn one for me on your lathe? Just kidding, thanks for the suggestion.

JB weld always worked on mine,have done a few,not just one,the oldest is over 20 years old now and still holding up. Getting the parts seriosly clean and a slight roughing up of the surface is the key.

Whats the OD of the of the carb neck? Do you have a caliper?

The pic of the olympic rear drum valve on Martin's site has this type of repair.

Guys, my experience with JB Weld wasn’t that great. I repaired a carb with it and thought it came out fine. But about half way thru the first flight the motor started to run rough. I landed and saw that the carb repair had turned to doo-doo. The JB had turned into a bright GREEN gooey mess. Never used it since (around nitro) but I see lots of folks have good results.
Any ideas what I did wrong? It could have been a sloppy mix proportion or maybe it had exceeded its shelf life? Maybe whatever I used to clean the parts (don’t remember) wasn’t compatible?
Anyone else seen this?
Al

Did you use JB Kwik or the standard JB weld? I have used JB weld on the exhaust repair of a crashed Evo 52 engine. No problems with it whatsoever.

Jason

Jason_WI wrote:Whats the OD of the of the carb neck? Do you have a caliper?

The pic of the olympic rear drum valve on Martin's site has this type of repair.

I do have calipers and a micrometer. I will take a measurement tonight.

I'll go check on Martin's site.

I have had the regular JB Weld darken in color around nitro, but not goo up and slide off. You might have had a bad mix or some contamintation of some sort Al.

The Quik is a 10 minute set, 24 hr cure and is more heat sensitive and brittle. I let the regular JB weld cure for 48+ hrs. under a 100 watt placed close to the part.