Broken Float Post Repair

Bought some VM28 pumpers off ebay in June and just got around to working on them...only to find a broken float post in one of the carbs. I'm pissed, both at the seller and at myself for waiting so long to check them out. I've seen lots of busted float posts in BS CV Mikuni's, but this is my first experience with a broken post in a VM. Paypal says there is a 180 day window to initiate a dispute, which I'm very tempted to do, but before going down that road I thought I'd post here to see if anyone has come up with a righteous repair method. I'll be reselling these carbs so the repair must be solid and above reproach. NO JB WELD suggestions please.

The break is near the bottom of the post and after cleaning off some crappy epoxy, the pieces fit together nicely.

BTW, the epoxy bond had failed....thus my refusal to use anything like JB Weld.

Found an old thread where the post was welded. That may be the way to go... kzrider.com/forum/3-carburetor/535889-br...post-can-be-repaired

If you are doing it to resell then the laser welding has to be the only real option.

Have a look at this post on the UK Z1 owners site.
z1ownersclub.co.uk/phpBB3/viewtopic.php?f=3&t=47409

I also think nothing short of welding would be viable, but...

I have used that Alumalloy on some aluminum repairs and engine case repairs. There are a few different trade names for it. It's essentially a solder or braze-weld system for aluminum where the weld rod melts at a lower temperature than the base metal. But it's hit or miss.

On some test pieces, the repair was stronger than the base metal and during destructive testing the base metal deformed and broke before the "weld " let go. That was surprisingly effective.

But other times the weld rod doesn't flow and fuse properly. And there is a possibility melting the base material. If you've ever heated things like carb bodies, you probably know that it can suddenly melt and collapse without warning. The outer oxide layer acts like a bag and the metal inside suddenly "deflates" away and drips out somewhere else. ..very frustrating.

I used propane only (as recommended) for that since it's a lower temperature rather than trying to regulate a hot MAPP flame. Cleaning off as much oxide is key. While heating, you use the weld rod to scratch though the remaining oxide during the process to get it to "wet" the base metal. If there is too much oxide, it doesn't wet and the weld won't take.

I'm 95% sure that I'm going to send this carb body off for welding. Body is bead blasted nice and clean so hopefully there will be minimum contamination getting into the weld. VM's are made of (pot metal) zinc, so aluminum brazing type repair is a no go. I've tried that stuff before on an attempted (and failed) fin repair job. It's really hard to get all the parts up to proper temperature in order to braze it together. The main part is a heat sink and the tiny fin (or float post in this case) is super easy to over heat.

There’s a fellow in Canada that specializes in this type of repair. He machines down the remaining post, installs a short length of threaded rod (probably about 2mm diameter) and machines a new post which then threads onto that rod. I feel like it’s less of a crapshoot than welding. It costs about US$100 so it may not be worth doing on your specific carb set. I had it done on a couple of RS36’s so it made sense in my situation.

He’s not an advertiser here so I won’t mention his company name but it can be found pretty easily with an Internet search. Total turnaround times in my experiences were 3-4 weeks (including Customs from and to the US) during the peak of the COVID delays.

Have seen my share of the broken post syndrome, easy reliable fix though. Don't have any pics but line bore the remaining piece post straight down thru where the float pin goes into the body. Tap an m3 allen grub screw thru both remaining post piece and body of carb. Plenty of meat under the post towers so plenty of room to tap. I use a starter tapered tap and finish with a flat ended. Tap the loose piece first, it's easier. Set into the fractured carb body, should self-align, hold tight and finish out threads till you bottom. You get the idea though.

That Canadian guy is in Ottawa, he repairs a lot of snow machine carbs. Its called Chinook Fabrication, he machines the broken post and fabricates a replacement post, then bolts it in place. I have not used him but I did look at his web site to get ideas on how to do it if I was ever in that situation. I have a small mill and lathe if I ever need to do such work.

The dude with the welder charges $35 and has an excellent reputation. I plan to send the carb out tomorrow.

The break is on an angle. It would have to be milled flat and a new post fabricated before drilling and threading the parts together could be contemplated. I suspect it could be done but I doubt it will be as good as the weld repair.

Only $35 is it worth for a post repair!

Carb body is on it's way back to me. Seems pretty good. Repair guy didn't want payment until I get the carb in my hands for review. He seems like a real stand up guy. He's called me several times during the process. He takes pride in his work.