Any Keihin Butterfly Knowledge?

[96flhpi]

For some strange reason I'm looking to put the stock Keihin butterfly back on my '82 FLH.  I pulled it because of the typical cough/sneeze issues.  No real complaints about the Keihin CV on it now other than mileage dropped from upper 40's to upper 30's and kicking with the CV is a crapshoot. 

Bike is stock except for Andrews J cam, K&N air filter and the 2 into 1/cigar muffler type system everyone's ragging on in the "Gasbox" thread except it's Paughco.  Not looking for performance, this is my daily transport.

Searching online it seems bumping the main jet to 175 is generally agreed upon as a good starting point to cure the sneeze but for the pilot jet I see recommendations for everything from one size up, from 70 to 72, all the way up to 98.  I know Im gonna need an assortment to dial it in right but there's like 11 sizes between 72 and 98.  BTW I buggered up the frozen jets that were in there so badly getting them out I can't read what they were.

I already have a 78 pilot and and 175 main.  I would like to order 3 or 4 pilots and 1 or 2 mains.  I'm hoping someone experienced can point me in the right direction as to what range I should have on hand so I can get it tuned without a lot of downtime.  I'm thinking I'll get 170 and a 180 mains but I'm lost as to what I should get for the pilots.

Any advice is greatly appreciated.

[76shuvlinoff]

Be interesting to watch this thread. I have had my original sitting on a shelf in the basement for 23 years. I never got it right but these day I think a lot of that trouble might have been caused by exhaust choices.

[bump]

I had a Keihin carb stock on my 78 shovelhead. Worked good for 4 or 5 years then couldn't get tuned right, it kept sneezing and coughing. Changed jets several times but no luck. Went out and bought an S&S B and it was simple to dial in and have been running it for 35 years.

[a_disalvo]

Many years ago, one of the mags of the era had an article about blueprinting those carbs. I did it and ran that carb for several years before changing to an S&S super B, gave it to a friend, he is still running it on his "82 FLH. Frank

[96flhpi]

Many years ago, one of the mags of the era had an article about blueprinting those carbs. I did it and ran that carb for several years before changing to an S&S super B, gave it to a friend, he is still running it on his "82 FLH. Frank

Yeah it's an Easyriders article.  I've read that and watched a bunch of YouTube tutorials that all have great tips but they just generally say bump up the jets without giving any suggestions what to bump them to.

[tomfiii]

Make sure it's clean,check accelerator pump to make sure it's pumping ok as sometimes the ball doesn't seat properly and the second pump is inadequate ,there could be a delay before actuating due to too much clearance at end of plunger. You shouldn't have to go too big on jets, make sure you use aftermarket intake with "o" rings and not compliance fittings. The butterfly carb will have a bog if opened too soon ,too fast.

[JW113]

Stock Jets:

Low altitude
Pilot: 0.70                27895-78
Main: 1.65                27898-78

High altitude
Pilot: 0.68                27894-78
Main: 1.60                27888-78

-JW

[96flhpi]

Thanks for replies all but I was really hoping someone who has a non coughing butterfly on a similarly set up bike would chime in with what size jets worked for them so I can narrow down the range I need to buy.

[JW113]

Dude. No one can dial in your bike over the internet. Start with a baseline, and tune it from there. Either do this the "hard" way and fiddle with it your self, or take it to a shop with a dyno and let them tune it. There is no magic pill to make your bike run perfect.

-JW

[guppymech]

In the past I've used number drill bits to change jet sizes on ones I had that were too small.  Some jets have a small chamfer leading into the hole and when you drill those the flow doesn't exactly match a stock sized jet though.  From what I remember I don't think the butterfly Keihin's jets are like that though.

[96flhpi]

Dude. No one can dial in your bike over the internet. Start with a baseline, and tune it from there. Either do this the "hard" way and fiddle with it your self, or take it to a shop with a dyno and let them tune it. There is no magic pill to make your bike run perfect.

-JW

I didn't mean to sound ungrateful in the last post nor in this one, but I'm not asking for a "magic pill."  I'm not asking for anyone to dial it in for me over the internet.  I'm asking the collective experience of this forum if someone has done this before and can tell me what size worked for them.  I don't expect that that size will be perfect for me, and as I originally stated I know I'm gonna need a range of jets on hand to get it done without a lot of downtime waiting on mail orders.  However, I'd expect that if, for example, a 78 jet worked for them I can not bother looking at jets in the 90's, but instead get 75 through 82 and at least be close.

[JW113]

I think you're asking for somebody that has the exact same engine configuration (a/c, carb, cam, exhaust, ignition, heads, pistions) and lives at the same elevation as you do, AND is using a Keihin butterfly carb. How likely do you think that is? All of it will impact the jet sizes. I think the short answer is, perhaps go with your origial plan (78 and 175) and see how it runs? I posted the factory jet sizes, and from what you posted, your bike is not altered dramatically from stock. If it were me, I'd be leaning more toward a 72 pilot jet to start with.

-JW

[96flhpi]

Thanks, yeah I'm gonna order 72 thru 80 pilots, and 170 thru 180 mains and see how it goes.

FWIW one guy says use a paper air filter rather than the K&N.  I guess I'll find out if he's right

[carioux2008]

Ive had pretty good luck with my Keihin butterfly on my 84. Ive got 1-3/4" drag pipes with a good clean foam filter in a teardrop cover. ACC pump set in the medium position. 170 main and i think a 68 or 70 pilot. Im debating going up to a 175 main as I'm getting some slight backfiring on decel. Id rather be a little rich than spot on or lean. I noticed a large improvement after switching to the drags and nice air cleaner; engine ran smoother and started easier. I didnt change the jetting though. P/O had those jets installed for whatever pipes he had on there years ago, im not complaining though!

Dont give up on the Keihin and give in to the S&S or CV guys. These carbs were designed to run on our old girls, and when set up right they do a fine job controlling the air/fuel mix. If your curious, compare your Keihin to the S&S and you'll see they are VERY similar in design. There are some differences, but close enough for me to not care.

One more note, my stock bore, stock carb, drag piped, 5-speed shovel outran my old mans 2017 103 TC fuelly piped tuned $20k roadglide ultra...and did it with style!

[david lee]

Be interesting to watch this thread. I have had my original sitting on a shelf in the basement for 23 years. I never got it right but these day I think a lot of that trouble might have been caused by exhaust choices.

mines been in the shed cubbard for around 30yrs with the choke assembly.was thinking of tossing it but put it back for some stupid reason

[david lee]

I had a Keihin carb stock on my 78 shovelhead. Worked good for 4 or 5 years then couldn't get tuned right, it kept sneezing and coughing. Changed jets several times but no luck. Went out and bought an S&S B and it was simple to dial in and have been running it for 35 years.

me too.i could remove and replace mine with my eyes shut. so easy to work on if need be

[Burnout]

A CV carb is a step or two better than a plain butterfly carb.

A CV will easily give 40+ MPG.

Fiddling with the main jet will not fix sneezing.

You say you are not concerned with performance, yet you complain about mileage, starting, and sneezing (these are all performance issues).

That jacked up exhaust will not help starting. You need to get the exhaust out of the motor without the "cross traffic ahead" and "detour" signs!

[96flhpi]

C'mon man, you know full well when I said performance I meant "go fast"

[motorhead_smf]

For some strange reason I'm looking to put the stock Keihin butterfly back on my '82 FLH.  I pulled it because of the typical cough/sneeze issues.  No real complaints about the Keihin CV on it now other than mileage dropped from upper 40's to upper 30's and kicking with the CV is a crapshoot. 

Bike is stock except for Andrews J cam, K&N air filter and the 2 into 1/cigar muffler type system everyone's ragging on in the "Gasbox" thread except it's Paughco.  Not looking for performance, this is my daily transport.

Searching online it seems bumping the main jet to 175 is generally agreed upon as a good starting point to cure the sneeze but for the pilot jet I see recommendations for everything from one size up, from 70 to 72, all the way up to 98.  I know Im gonna need an assortment to dial it in right but there's like 11 sizes between 72 and 98.  BTW I buggered up the frozen jets that were in there so badly getting them out I can't read what they were.

I already have a 78 pilot and and 175 main.  I would like to order 3 or 4 pilots and 1 or 2 mains.  I'm hoping someone experienced can point me in the right direction as to what range I should have on hand so I can get it tuned without a lot of downtime.  I'm thinking I'll get 170 and a 180 mains but I'm lost as to what I should get for the pilots.

Any advice is greatly appreciated.

I ran a similar pipe to that when I first got my 68.  I played hell getting the rear pipe to seal into the header.  An exhaust leak at that point could cause some issues as would at the heads.  Something else to think about if trying to dial in an air/fuel ratio.