$%^^$#@ keihan carbs


i like em i really do..about the easiest carb to tune out there and easily on par with mikuni..but one thing boils my blood to no end is how keihan/honda mounted these vintage carbs on our little bikes...an m6 screw through the intake flange into the carb cheap pot metal with keihan adding a boss to get enuff threads...ok sounds great but the problem is kids of yore (same as today) like to torque the living hell out of those little m6 screws which quickly stripped out the threads in the carb...i wish like heck keihan/honda had simply drilled a pilot hole and used a m6 nut on back of the m6 bolt..no worries though...took carb apart (stripped bolt=air leak i found) and after setting up the mill-milled a nice flat spot on the boss which is now somewhat smaller...i used a #2 bit to eat out those stripped threads and followed with a #1 bit to finish the job....new m6 nut was carefully sanded so it would fit in the very minimal space....put carb together after careful sonic tank spa bath (cleaning)...new longer m6 bolt and with speshul nut no more air leak....shoulda been done like this at the factory..but honda if nutin else was very adapt at efficiency and well it was just easier to thread the carb and have line worker screw it together..end result is a factory looking job that will not loosen and cause an air leak which most know can burn valves and glob out the piston...i did look at helicoil..which i despise..so this little repair was in order and problem solved 4-ever

ps:another thing i have found with both keihan and mikun carbs is the flange face (o-ring side on keihan) is not all that true ..you may want to wet sand that flange face to get a far better seal then factory (sorta mini blue-printing your carb aspect)..i do the same process (wet sand) on both flanges of the intake..i have found this simple process can make huge difference in never having to fight an intake air leak

ps: i STRONGLY SUGGEST a leak down test to help you find and isolate air leaks..its well worth the time..i must add i am as guilty as anybody in being lazy in this regard
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I've used stainless thread inserts from McMaster-Carr in the carburetor as well as the engine cases, head, etc.

Drill and tap 3/8 x 16 (inch) and sock them in. They have a thread locking compound already on them.

97120A11018-8 SS Self-Locking Thick Wall Insert M6-1.0 Int Thrd, 3/8"-16 Ext Thrd, 13/32" long.