Re: Bigtwin 40hp 1963
I have the same motor and I need a carb kit / float. This link looks like its for a different year not a 63. Anyone have any input?
I have one too. The "exploded view" picture that tashasdaddy posted is the carburetor that I have. It has the water heated choke and only low speed adjustment.
To rebuild it, clear a work space and try to remember how things come apart.
Disconnect hoses, take out the plug from the float bowl (to drain it,) disconnect the linkage, then take it off, (I had to loosen the recoil starter and remove the starter motor to get at it.) Take the low speed needle and packing nut off, take out the packing and washers from behind the nut (using a pick or piece of wire.)
Look at the needle tip for wear. If it has any, you'll have to replace it.
If you have a different model with the high speed adjustment, remove its needle, packing nut and packing.
Then take the float bowl off. Pull the hinge pin from the float, remove the float and needle. Take out the needle seat (this can be tough, use the correct size screwdriver.) Completely remove exposed gaskets.
You don't have to take any thing else off.
Check to see if either throttle or choke shafts are sloppy or loose in their bores. I mean they should twist but not wiggle side to side. In and out some is OK. If they wiggle you are S.O.L. get another carb.
Clean with solvent and
blow out ALL the air passages. (holes that don't have screws.) Pay attention to the low speed (where you pulled the needle out.) and the high speed (bottom of the float bowl, behind the plug.)
Crud can build up in the bottom of the bowl and block the high speed orifice.
The kit comes with gaskets, float needle & seat, packing/washers (for high & low speed needles.) Some kits include the float and hinge pin. (if your float floats then it's OK.) My kit came with some press fit plugs (cupped disks) you won't need them, DO NOT replace them.
To assemble, insert nylon washer, two packing rings then a metal washer then packing nut (loosely) into the low speed needle orifice. Screw in needle till it just seats then back it out 1-1/2 times. Tighten the packing nut till the needle is stiff to turn.
For the High speed (if equipped,) use 4(?) packing washers and turn it out 3/4 turns from lightly seated.
Screw in the new float needle seat tight, with a new gasket (nylon/fiber.) Be careful to not booger it up. Drop the needle in, then put the float and hinge pin in over it. (Use new ones if supplied in the kit)
Turn the carb upside down examine the float. It should hang parallel with the bowl. When rightside up the needle should move up and down with the float.
My kit came with a small spring that holds the needle to the float to pull the needle down. It was a pain getting it hooked right. It kept falling off or getting hooked crooked jamming the needle. I managed by hooking it like a safety pin around the needle.
The needle Must move freely up and down with the float.
Put in new bowl gasket, tighten bowl evenly. Put bowl plug in with new gasket, tighten firmly.
Put new carb to intake gasket in and install carburetor. Connect linkage, fuel and water lines, (Don't mix them up...)
Re-attach starter(s). Be sure to synchronize carb with magneto.
I also have a 62' Johnson 28hp that has a very similar carb, It has an electric choke and the highspeed needle. The housing & linkages are the only difference.
Did I miss anything???
