Have posted about this before and have made some progress but it still ain't quite right.To recap it is running very lean and coughs at high revs.
I have been advised by a Harley mechanic here in UK that seems to know his stuff that replacing the rubber intake manifold with a solid one and replacing the back of the air box and running a K&N filter, then re-jetting main jet to 180 should fix the problem.
Anyone else heard of this as a fix and if so what parts are used? I want to maintain the originality of the bike as best i can so DO want to keep the original air filter cover, everything is pretty buried and would be visible.
He's going to charge me a fair bit for doing this and I would like to have a second opinion on whether it's going to work.

 

You would probably be better off getting rid of those compliance type fittings and go with the later CV carb and intake manifold. Plenty of carbs and intakes on ebay. I believe you can still use your air cleaner

 

You are not the first to have suggested this and perhaps trying to keep things original isn't a good idea in this instance. It might in the end be cheaper to replace it with the CV as you suggest… although I would need to fashion some of way of maintaing the choke arrangement.

 

There are brackets available to mount the choke right to the carb..

 

I threw my stock compliance fittings in the trash in 1988 when they were brand new and went with a Ram Jett solid manifold. I'd had enough of rubber effing boots on old Japanese motorcycles. They are born to leak as they age.

It's worked flawlessly since.

The later manifold with ring seals isn't quite as good as a Ram Jett but those are only available used. (I buy them and make gaskets as well as turning down any Allen bolts I buy for them if the heads are a few thousandths wide. I basically remove the knurling.).

The conversion to either is worth it. So is a K&N element which last many, many years.

You can keep your stock airbox.

I would rejet the stock butterfly carb and make sure it has the Andrews or other accelerator pump check valve. I did this on many HDs including mine in the '80s. Works just fine. HD used to supply accel pump covers with check ***** but phased them out for emissions reasons. The pump cover kits are about twenty dollars. If your removed pump cover "rattles" when shaken it already has the check ball.


I would go up one jet size on the low speed jet too. Low speed jetting greatly affects midrange.

Back then we didn't bother buying low speed jets. We kept cheap sets of #60-80 drill bits and went up one SHANK size from the largest shank diameter which fit. I still do it that way. Grip the drill shank in a pair of mole grips, then spin the low speed jet gently between thumb and forefinger while applying gentle pressure. When the jet slides over the drill, stroke it back and forth a couple of times without rotating the jet to deburr. Inspect hole using bright light and reinstall. (My mentor taught me this and he's been drilling jets since the 1950s on all brands, his Rapide included) I just bought a fresh set of bits via Ebay for about seven dollars.

Allen head bowl screw kits are cheap. I greatly prefer them to the stock Phillips screws but your call.

This is a very basic project so if you'd like to get your feet wet it would be worth trying yourself. IMO a shop should not bill over about three hours labor if all the parts are in good shape.

The CV is an excellent carb but a properly tuned butterfly Keihin is fine for a stock engine and though CV diaphragms are cheap and easy to replace, the butterfly lacks that additional point of failure.

 

Monckywrench is spot on.

I'm running a s&s solid manifold and the original keihin butterfly bolted to it. I have a k&n filter in the stock air box so everything looks original.

The Andrews accelerator pump is a nice upgrade as well.

Yes a CV would probably be a better route but a properly jetted butterfly runs just fine.

 

A properly jetted, tuned, magic applied stock 1986 carb is still a total POS, in my opinion. It was a piece of shiite in 1986 and it's a piece of shiite today. The compliance fitting manifold is also a major failure point. Don't know how many of those I replaced.

I suggest either a S&S setup (carb and intake) which I have personal favorable experience with or a CV which many others like.

 

Depends on his budget too. I eventually threw Super Bs with pump kits on everything then Es when ethanol-resistant accordion boots and plungers for the Bendix-style aftermarket B pumps became necessary. My Evos and Shovels with S&S all have cams and freer flowing exhausts to benefit from the larger carbs.

OP has a very stock machine. Not to get in a whizzing match, but what other than modest horsepower do you see as a problem with the butterfly carbs?

I've sorted plenty on big twins, and when owners added larger carbs I got their old Keihins and replaced worn out Bendix and Tillotson carbs on customers older models with them. No leaks, no cold natured starting with the EPA lean issues solved, and customers rode off happily.

I threw away the choke plate and shaft on mine once rejetted but I live in SC which doesn't get cold.

OP is in the UK where they probably don't have piles of free and cheap Harley parts like many of us do here.

His call on what to spend. Speed costs money and you can always spend faster.

Whatever he chooses he can get bolt-by-bolt advice here since we've done heaps of carbs.

I forgot to mention orienting the accelerator pump nozzle when you remove the float bowl. Before removing the carb, remove air filter, open throttle and observe clock position of accelerator pump fuel stream. After bowl is removed, gently rotate the nozzle (it's a press fit) with a small Crescent or "ignition" wrench until the stream will be approximately centered in the carb bore.

 

My "thing" is vintage bikes especially American vintage and I was tired of riding look a like Japanese copies. I wanted a vintage ride for my daily commute (about 50mile round trip) The 40's Indian would have been to difficult. So the retro looking 80's HD ticked all the boxes. So I don't need rocket performance (the traffic clogged, pot holed icy roads would kill you) and I do want originality.. but only if it works. I take Dr Hess's points but I think I'm with monckywrench in working with what i have. Thanks for the tip on the pump, I bought one last night so now i need the manifold. Parts so far haven't been too hard to get but not cheap.
The Forum isa gold mine of advise and opinion and makes keeping this old machinery alive and been ridden. Thanks to you all.

 

My "thing" is vintage bikes especially American vintage and I was tired of riding look a like Japanese copies. I wanted a vintage ride for my daily commute (about 50mile round trip) The 40's Indian would have been to difficult. So the retro looking 80's HD ticked all the boxes. So I don't need rocket performance (the traffic clogged, pot holed icy roads would kill you) and I do want originality.. but only if it works. I take Dr Hess's points but I think I'm with monckywrench in working with what i have. Thanks for the tip on the pump, I bought one last night so now i need the manifold. Parts so far haven't been too hard to get but not cheap.
The Forum isa gold mine of advise and opinion and makes keeping this old machinery alive and been ridden. Thanks to you all.