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Broken Carb Float Post Fix!!
OK, I wasn't talkin' out my a**.... I really did come up with a fairly easy fix, with one caveat; it's real easy if you buy a pre-made 'kit' from me, a bit tougher if you plan on totally DIYing it. But here's how it works, and complete directions on how to do it if you're so inclined.
Typical broken post. This repair works as long as there's still some post above where the pencil is. Even if both 'tops' are gone, this fix will still work.
What you need for material. Top row: piece of 16 gauge (.050" thick +/-) aluminum 1.05" x at least 1.5" (longer will make it easier to work). To the right it's cut to shape except the 'ears' are still long. Bottom row: Finished bracket and the new longer float pin (made from the shank of a 5/32" pop rivet). You also need a #41 drill bit.
Dimensions. The critical ones here for proper fit is the 1.05" number, the .365" width of the 'ears', the 1.015" inside the 'ears' after you bend them, and particularly the location of the pin holes. All these need to be within +/- .002" for a good fit. The others you can cheat a bit, but do try to keep the 'base' where it contacts the gasket surface as wide as possible as it helps keep the bracket stable. Oh yeah, the new pin should be 1.170" long.
Here's the only mod to the carb body. The posts are tapered slightly, so you need to file them 'straight'. File slowly and carefully; try not to take any off the upper part of the posts. When you have this right, the bracket will be just inside of the gasket. When you get this right, the float bowl should slide on with a slight interference. Don't force it. Check your pin location at this time. If it won't quite go in, file the post just enough until it does. You can file off any small bumps on the top of the posts if need be. DO check the float bowl to make sure it's 'flat' inside (see first bowl pic). And the hole in the one post is left over from a previous repair, so ignore it.
Some (but not all) float bowls will have a 'ridge' here; if yours does, file it flat inside the bowl.
Here's pics of the repaired carb. Again, if all your dimensions are right, the bracket will slide right on and the float pin will line up with the existing holes. Several things to note here: first, the bracket base should be in contact with the gasket surface. Next, notice the 'dimple' in the top of the bracket; this is what hold the bracket firmly down. This dimple contacts the bowl, and is made with a center punch. A firm hit is all that's needed; you want this dimple to be .030" high, no more. One last thing; I 'tweaked' the lower corners of the ears in as this will hold the bracket in place.
This pic shows how the bracket fits into the bowl. If you did everything right, you should have .030" of the bracket hanging below the gasket surface, which is the thickness of the gasket.
Now, for what it's worth, these fit perfectly on the five carbs I have available to me. So I have to assume that Mikuni held their tolerances pretty tight, but that's not to say someone doesn't have one that's 'odd'. I'm going to sell 'kits' consisting of the finished bracket, a new float pin, a 'file guide', and directions for $25 including shipping in the US. If you order more than one, each additional kit up to ten total will be $20 (minus the guide). If you're out of the US, same pricing but shipping will be on top and the actual amount.
Mine are built by milling the aluminum to shape, then using a 'jig' to bend the ears and drill the holes, so I'm getting very repeatable results. There's still a bit of hand work involved even so. The only thing you need to install this kit is a file!
I'll also send a free kit to anyone who will donate a dead carb body and float bowl to me. Neither need to be good, just as long as the bowl isn't bent/warped, the bowl fits on the body right, and the carb posts aren't gone more than noted. I've been using a 'loaner' from Foreda (Thanks Dale!) but he does want it back!
One last thing; does anybody know what other bikes may share these carbs? I might put some of these up on Ebay (for a bit more money to non-forum people), and if they'll fit more than just the XS11, maybe I can make few bucks to feed my bike habit...
Any comments or questions?
'78E original owner
Typical broken post. This repair works as long as there's still some post above where the pencil is. Even if both 'tops' are gone, this fix will still work.
What you need for material. Top row: piece of 16 gauge (.050" thick +/-) aluminum 1.05" x at least 1.5" (longer will make it easier to work). To the right it's cut to shape except the 'ears' are still long. Bottom row: Finished bracket and the new longer float pin (made from the shank of a 5/32" pop rivet). You also need a #41 drill bit.
Dimensions. The critical ones here for proper fit is the 1.05" number, the .365" width of the 'ears', the 1.015" inside the 'ears' after you bend them, and particularly the location of the pin holes. All these need to be within +/- .002" for a good fit. The others you can cheat a bit, but do try to keep the 'base' where it contacts the gasket surface as wide as possible as it helps keep the bracket stable. Oh yeah, the new pin should be 1.170" long.
Here's the only mod to the carb body. The posts are tapered slightly, so you need to file them 'straight'. File slowly and carefully; try not to take any off the upper part of the posts. When you have this right, the bracket will be just inside of the gasket. When you get this right, the float bowl should slide on with a slight interference. Don't force it. Check your pin location at this time. If it won't quite go in, file the post just enough until it does. You can file off any small bumps on the top of the posts if need be. DO check the float bowl to make sure it's 'flat' inside (see first bowl pic). And the hole in the one post is left over from a previous repair, so ignore it.
Some (but not all) float bowls will have a 'ridge' here; if yours does, file it flat inside the bowl.
Here's pics of the repaired carb. Again, if all your dimensions are right, the bracket will slide right on and the float pin will line up with the existing holes. Several things to note here: first, the bracket base should be in contact with the gasket surface. Next, notice the 'dimple' in the top of the bracket; this is what hold the bracket firmly down. This dimple contacts the bowl, and is made with a center punch. A firm hit is all that's needed; you want this dimple to be .030" high, no more. One last thing; I 'tweaked' the lower corners of the ears in as this will hold the bracket in place.
This pic shows how the bracket fits into the bowl. If you did everything right, you should have .030" of the bracket hanging below the gasket surface, which is the thickness of the gasket.
Now, for what it's worth, these fit perfectly on the five carbs I have available to me. So I have to assume that Mikuni held their tolerances pretty tight, but that's not to say someone doesn't have one that's 'odd'. I'm going to sell 'kits' consisting of the finished bracket, a new float pin, a 'file guide', and directions for $25 including shipping in the US. If you order more than one, each additional kit up to ten total will be $20 (minus the guide). If you're out of the US, same pricing but shipping will be on top and the actual amount.
Mine are built by milling the aluminum to shape, then using a 'jig' to bend the ears and drill the holes, so I'm getting very repeatable results. There's still a bit of hand work involved even so. The only thing you need to install this kit is a file!
I'll also send a free kit to anyone who will donate a dead carb body and float bowl to me. Neither need to be good, just as long as the bowl isn't bent/warped, the bowl fits on the body right, and the carb posts aren't gone more than noted. I've been using a 'loaner' from Foreda (Thanks Dale!) but he does want it back!
One last thing; does anybody know what other bikes may share these carbs? I might put some of these up on Ebay (for a bit more money to non-forum people), and if they'll fit more than just the XS11, maybe I can make few bucks to feed my bike habit...
Any comments or questions?
'78E original owner
A pro could probably turn these out for about $1 each once you have the setup, but amortizing the cost of his $50K machine would no doubt run the price up some...
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