After much help by posts on this forum about keihins butterfly carbs (27029-88) , I have at last got my recently acquired FLHS of 89 vintage running well, after 20 years of storage and not being run. It had 3800 miles on the clock and its original front tire.
I thought I would write what it took to get my bike running properly, so that I may help someone down the line with the same issues.


Replacing old fuel, fuel hoses and the cracked fuel connector was the starting point, after which I bought a couple of carb rebuild kits/gaskets etc.
I had the bowl and integral brass accelerator jet sonic cleaned at my local mower shop, and cleaned the internal bunged up pilot and main jets. Search this forum and there is good detail about this process as well as float height etc.
I replaced the old compliance fittings, but was left with an awful no throttle to some throttle hesitation that no amount of adusting, cleaning and re-cleaning would shift. Revealing the external fuel screw from under the smaller blank piece enabled adjustment, but no improvement.
On reading another posters advice for the umpteenth time, I realised that replacing the 0.52 mm pilot jet with a 0.58mm (the next size up) was not the probable waste of time it seemed, as the hole would in fact be 25% bigger, and not the insignificant increase I had imagined .
Having replaced the pilot jet with the bigger one, my bike now has as good a pick up of throttle and as good fuelling as any v twin I have ever ridden. No carb popping, no misfire, all is good in my keihin world.
I have no doubt that I will one day take the advice many have given, which is to bin the keihin, but now it will be because one day I will chose to, rather than have to.
Thanks for all help received.

 

Good on you. I love my old butterfly carb. When tuned right it is a great carb.

 

Way to go, you have patience and kept at it. Glad to hear that is it running good for ya.

 

No matter what you do to tune that butterfly carb, it will still feel like you are pulling a trailer loaded with rocks...

The best thing I have done on my `89 FLSTC is to swap to a CV carb.

 

For short money a man can convert to a CV, and once you do, you'll wonder why you didn't do that a loooong time ago.
Scott

 

I don't agree with either of you posters. A well tuned butterfly will make a stock evo run as well as a cv carb.

 

Good luck trying to convince anyone who knows anything about Harleys to believe this...

No amount of tuning can make the butterfly carb equal a CV, Mikuni Smoothbore, or an S&S carb.

The Butterfly is an antiquated design that does not allow the engine to breathe enough air.

 

That is horse shyt. A stock evo will run no better or have any better throttle response than a well tuned butterfly. If you raise compression or bore size and stroke with cam yes the cv will work better. I have done this experiment.

 

You are not the only one who has done this swap...

Plenty of guys, (including me) have done the swap to a CV, and have noticed a noticeable increase in power and throttle response on otherwise stock engines.

I`m glad you are happy with your butterfly carb.

 

+1 The first and best mod.