I have a stock '89 Electra Glide. It has the Keihin butterfly carb. I rebuilt it a couple of years ago and tweaked it per an old Easyrider's article I found online. It runs great and I get around 45 miles a gallon.
My old butterfly coughed all the time. The dealer that I bought the bike from said "Ignore it, it's normal". It also would not start in cold weather, at all, no way. The S&S will start in cold weather and never coughs. My old guitar teacher used to say that perfect pitch on a 12 string guitar was when you threw it into the dumpster without hitting the sides. That's how I feel about the butterfly carb.
The very first mod I made to my bike after buying it was to replace the balky, coughing butterfly carb and the compliance fittings etc. with a used CV carb and manifold. It made a world of difference.
FWIW, if you have an old Keihin butterfly, or an even older Bendix, and have the cough, richen the idle a bit (idle screw on Bendix; idle jet on Keihin).
I ran Bendix/Zenith butterfly carbs for quite a few years with little trouble once they were set up properly. The Bendix has only 2 real adjustments - replaceable (later had adjustable) main jet, and the idle needle screw adjustment. Idle and low speed ops depended mainly on the correct setting of the idle adjusting needle screw. As rpm increases (butterfly opens more) holes are exposed in the roof of the carb, allowing more fuel to enter the carb throat, until the throttle plate is opened even more and then the main jet takes over. The Bendix can be rebuilt time after time; biggest problem now is junk parts in most rebuild kits. Not saying it is a great carb, but if you have an old bike with a Bendix and it works, just smile and ride. If/when you go hotter on the engine, or the carb just won't take a rebuild, then replace it.
When the Keihin replaced the Bendix nearly all of them had the lean sneeze/cough. Richening the idle setting with the low speed mixture screw usually only cured it about half the time, and often led to some bogging just off idle. The low speed system was for idle, low, and mid speeds. But the Keihin slow jet could be replaced with diff sizes to tune the carb. Most times I found a drill bit that would just slide into the jet, then go up to the next size bit and hand drill the jet out, emphasis on hand, as in twirling the drill bit between the fingers. That cured the cough.
Before doing anything to the carb, whether Bendix of Keihin, make sure the manifold doesn't leak. There were 3 varieties of manifolds and seals, o-ring, rubber band, and compliance. The band was s'posed to be an improvement over the o-ring, and the compliance even better, but I liked the o-ring with a simple modification - slip the o-rings in place between the manifold/head and then wrap a couple turns with some Scotch 33 electrical tape. Don't use cheap tape, and don't use Scotch 88. Another tip is to center the manifold between the heads when assembling the engine, by leaving the head bolts loose, installing the manifold with o-rings and no clamps, and then moving the heads until the manifold-intake port gaps are equal, then snugging the head bolts, removing the manifold, and torquing the head bolts. Doing the head/manifold centering, and using the tape on the o-rings made getting a good seal easy.
But that o-ring stuff doesn't matter 'cause the Keihin butterfly carbs on Evo engines used the compliance fittings, LOL. I've heard a lot of folks cuss 'em, but if they are in good shape they are way easier to make seal properly. At any rate, carb adjustments are worthless if the manifold leaks!
Thank everyone so much! this type of feedback is exactly why I'm excited to be part of this forum. I've got a lot of learning to do and the help from you is much appreciated.
OK, I've taken advantage of the sunny and windy Cleveland weather. I have a OEM KEIHIN BUTTERFLY CARBURETOR #27029-88.
Does anyone have a parts list or diagram? There is a piece that I think might be broke or missing something. Here is where my "newbie-ness" will flourish, but it's also how I'll learn. The pic attached, the back side just has a look like it's cracked and shouldn't be.
Depending how much it is cracked, and exactly where, if air in-leakage can get into there, it will mess up the low speed mixture. I've attached a diagram of a an older version of the carb. Basically, everything is the same, but the old versions do not have the shroud around the low speed screw.
It's cracked pretty good, so I'm most likely going to upgrade to a CV carb. I've seen post were I would need a new manifold, and I've seen posts that I would only need a flange adaptor. Any suggestions welcome...
04-07-2015, 07:54 AM
