Broke carb now. Repair? Replace?

'82 XJ750 Maxim. Tore the carbs down tonight. All was going swimmingly until the last one. Opened it up and found this. It had been glued or epoxied in place with some silicone like stuff that had presumably held for a while. I have the piece that came off.

So a couple questions : any chance of repairing this? What goo will hold up to gas.... JB weld?

And if it's not repairable, or if I just get too disgusted with the idea of a float just waiting to rattle loose, what model bikes can I look for a single carb from? 650 Maxim if I swap in the correct jets from this one?

And this is carb #2. Are there any physical differences besides the fuel rail holes in the 4 carbs? If I got a carb with the fuel hole plugged on one side, can that just be drilled out to work in the #2 spot? The bowl on this one is fine and could be used on an opposite handed carb.

The good news (I need some) is that the soda blasting is working quite well.

 

As far as I know, the HSC32 bodies are interchangeable between models (Yamaha versions), only differing in the jetting. I may be wrong. Also, I think the #2 and #3 bodies are the same, #1 and #4 differ because of the fuel rail openings. (On the 85/86 XJ700 airheads with HSC33's, all four are unique)

Last year I sent a rack to @hogfiddles for a rebuild. Turns out one of the float towers had been repaired in the past. To make a long story short, there wasn't a replacement immediately available (HSC33) and Dave determined that the repair was pretty good, so we left it alone. It is still fine. That being said, I have since acquired a spare and put it on the shelf for if/when it gives out.

Anyhew, the repair looks like it was done by somebody who really knew what they were doing. Like a pro machinist or something. The repair consists of two holes drilled into the base and the tower, and then copper wire pressed into the holes to hold it (at least I think it's copper wire). You can kind of see it in the photo below. Maybe @hogfiddles or somebody could provide better instructions on how to do a good repair like that.

Common wisdom is that the JB Weld repair is crap. That being said, I took apart a junk rack last year that had a JB Weld repair that must have lasted for a lot of years. I may still have a good #2/#3 body from that rack sitting around.

In my opinion, you've got three options:
1. Be patient, get a replacement body, and DIRTFooT (do it right the first time)
2. Do a janky JB Weld repair, get a replacement, and replace as soon as convenient.
3. Do a "pro" repair, work on getting a replacement, but it may be less urgent. (this is the situation I'm in - "good" repair is holding up, but I've got the replacement on the shelf)

Here is the repair:

 

Carb bodies #2 and #3 are the same , and are used on all XJ650 (non-turbo) and all 1981-83 XJ750 models. Note that early (1980-81) XJ650 carbs used a coarse-threaded mixture screw, whereas all XJ750 and later XJ650 carbs used fine-threaded mixture screws. Although you can mix the two different (thread pitches) on a single carb rack, it would be best if you didn't. We should have a good used carb body available if needed.

 

Here is a video of a post repair for an XS1100 Yamaha. Base of post is wider though. Perhaps an engineer could repair your damaged carburettor..

 

Dan, after seeing your repair it gives me slightly more hope that I could fix this. The JB Weld, or any other epoxy by itself is likely not enough, but pinning it...maybe? The video that Franz links shows a complete post replacement which looks solid, but yes the post is wider on that carb. I think I'd need some delicate tools and better eyesight!

Maybe I'll take a stab at it while looking for a replacement. Can't make it much worse than it already is.

 

There is a shop that can re-weld (or re-create) broken posts: www.jmfmicroweld.com

If you have the broken-off piece, then the cost is no too great. "Creating" a missing post section can get a bit more expensive.

 

Well I gave it a shot at repairing. Using Dan's repair above as a model, I drilled two holes to accept some 1/16" brazing rod. After the first photo, I removed the rods and chewed them up a bit with the dikes to give them a rebar-ish surface. Then JB Weld in the holes. It was tight enough to tap into place with a hammer. Put the float pin in as a guide for the final tapping, just sighting it parallel with the carb body. I was going to fill the void next to the needle seat and glob some more JB Weld up the inside of the post as a gusset of sorts, but just the two pins made this really solid, so I think I won't risk the additional gunk that might fall off into the bowl. I think it'll work!??

 

That looks pretty darn solid. I wouldn't trust myself to try to drill little holes with that level of precision.

Nice work. That should get you by for a while.

 

I disagree, if JB weld is properly applied and fully cured it will last a long time , liquid steel is another product that works great and stand up to fuel . One set of carbs I have had carb body with a broken post from some point . I took off the epoxy that was on there , drilled a pilot hole in the post and the body , used a post of a broken drill but , applied JB weld and used the carbs for two years , I swapped out the carbs checked them and was still solid. At least for me this has worked fine .

 

@Jetfixer - I think there is a difference between a repair that is a combination of some mechanical structure with epoxy to kind of hold things together versus a repair where ONLY epoxy is used.

I would have a reasonable amount of confidence in the repair that you or @Roast644 did. There is a structure in there besides just the epoxy. Kind of the same principle as carbon fiber - the resin alone is brittle, but if you combine the resin with a carbon fiber cloth it becomes very durable.

I would not have a lot of confidence in a repair consisting of the post simply glued on with a glob of epoxy. I don't even think its got to do with being eaten by fuel - I think that after enough vibration, heat cycles, and whatnot that it will fall apart. It will work for a while, but the clock is ticking.

Regardless of repair method, I think you need to put a replacement body on your proverbial "list" of things to do. The better the repair, the less urgent the need for replacement.

 

When I wascin high school I worked for Ditch Witch the treachery on one model used a Dana 44 rear end ( 4x4) they would crack on the housing just enough that they would seep from the cracks. The housings were cast iron so welding was really not an option , we cleaned the housing up , stop dilled ends of the crack roughed up surface and filled area with JB weld , saved owners a lot of money my time there we only had one come back ...the owner ran over a big rock and cracked the pumpkin around where we repaired it..this time we had to put in a new unit. My volkswagen beetle, aluminum engine case the oil pressure sending unit boss cracked , proper repair would have been to tight weld ...but would have meant tearing down engine. I got a brass threaded collar built up area with JB weld this has worked good for six years and is oil tight and VW aircooled engine run pretty hot and this area has up to 60 psi of oil pressure at least on cold start and drops to 30psi when hot . I used to hang out at the local drag strip , a racer and engine builder had a Hemi with a crack on the engine block near a water jacket freeze plug , out came the JB weld , the next day he ran low 9's in hid 71 Dodge Dart with no leak . Will JB weld work every time...of course not , it will not take any torsional load , and a carb post there are no loads and again as long as you do the proper procedure of roughing surface put a pin into post should last for a good while.

 

That's the key.