Harley Stage 4

Harley Davidson Performance Upgrade Stages

Basil General Leave a Comment

In Harley terms, staging follows fairly set patterns. It’s not a general thing you actually can stage any motor and the prices can vary wildly but to get us going let’s look at the basics:

Harleys straight out of the factory have the fundamental issue that they notoriously find it difficult to breathe properly. The reason for this is down to HD needing to meet noise and pollution regulations. There’s an expression floating around – “Harley Tax” which seems to have the notion of HD squeezing even more money out of your original purchase by recommending extras that you should get to get the bike that you want, this really isn’t the case though. UK bike specs are tightly regulated, even more so than the UK law demands and that is because  there isn’t actually a “UK spec Harley” it’s just more cost effective for HD to make a small amount of alternative specs as possible which means the riders in the USA get the same model (apart from California) and everyone else (apart from the Swiss) get the International version (by the way the Swiss and California models are even more restricted with catalytics converters due to market demands).

The fact that these out of the factory bike don’t breathe as efficiently as they could isn’t an issue for most people because the power output is more than enough for most people. But for those who want that extra bit of power and are willing to part with their hard earned cash for it there are a number of tweaks that can be carried out, the first upgrade being “Stage One”.

Before we start, this isn’t meant as an absolute “thou shalt fit a ” because we don’t work that way, and because experts will disagree with each other, and with us. There is no such thing as a definitive guide to staging, and there is no absolute right way to go, but this will hopefully put you on the right path.

Harley owners will read this article and probably disagree with some of it’s content and with each other too and that’s fine. The truth is there is no definitive guide to how to stage your Harley, no wrong or right way to do it (apart from some cheap and nasty methods such as drilling holes in the plastic air-filter backplate which is just right at all), there are just “ways” to do it so the aim of this article is simply to point you in the right direction and let you decide how to proceed.

Let’s look at Harley-Davidson Stage 1 (click here)

Harley-Davidson stage 1 bikes are pretty easy to spot. For a start the air filter is the most visible part of the upgrade because it isn’t sunk into the plastic moulding in between the motor and air filter cover.

Harley-Davidson Stage 1 Horsepower Increase

In stage 1 there is no internal mechanical modification required all we are looking to do is to make the means of getting the fuel in and exhaust gases out more efficiently. There are more things you could do though such as including ignition modifications if this is within your budget. You can go as far as you want, but the most common basis for a Stage One is a High Flow Air Cleaner kit and a pair of slip-on mufflers.

You have to remember that the build of your bike when it comes out of the factory is within regulations and if you start messing with those specs you have to accept the responsibility that comes with flouting the regs.

If you are looking through parts catalogues you’ll start to notice the crossed chequered flags marked as “For Race Applications Only” and you will see these more and more often as you continue to stage your Harley.

Normally fitting an air filter is straightforward but when looking at a stage 1 upgrade you will quickly realise that one of the bits of emission control are the mounting studs holding the air filter backplate on – these are actually engine breathers from the cylinder head, hence why it is called a “kit” rather than a simple air filter.

The purpose of the kit changes the flow route and then it’s a matter of fitting the supplied filter onto cast mounting plate (which will have been adjusted) therefore allowing for greater airflow. It is just a case of then refitting the stock cover or supplied alternative.

Having let the air flow more freely, it’s essential to consider the impact on the calibration of your EFI or the jetting of your carburetor. More air means proportionally less fuel, and that means a lean mixture: sort it before you run it in anger, or it could overheat and potentially seize.

Assuming that the mounting bolts are still in good condition the Slip-on mufflers are easy enough on a new motor.Slip-on mufflers

These Slip-on mufflers provide less restriction for the exhaust gases and are louder as a consequence which is why a lot of people buy them just to make the bike LOUDER – which is enough for some people and is their whole reason for the stage 1 process. But you really don’t have to stop at this point.

Having got the air into the carb more quickly, and eased the path of the exhaust gases, it makes sense to make sure the fuel metering system is working as efficiently as possible so you want to have a look at that – and there’s more to fuel systems than jetting and the recalibration of stock EFI modules.

This is where things can become contentious. There are many ways in which you can sort out the original CV carb from a Dyno Jet kit to throwing it away and replacing it with a slide carb, and your decision will largely depend upon who you speak to but your decision will likely be based upon how much experience you have of tweaking carburetors, how much you’ve got to spend and whose advice you most trust. As regards to EFI, the stock unit can be recalibrated to account for the changes, on a dealer’s rig, but Harley themselves don’t offer alternative units beyond that calibration, and your warranty will suffer if you play away.

Dynajet Kit

Carburetor jetsHarley supply different jets for their Keihin carb and, if you know what you’re doing and have access to a Dyno to speed things along, then this is definitely is as good a starting point as anywhere. The factory-supported DynoJet recalibration kit is a common alternative to take a lot of the guesswork out and can be backed up by their Thunderslide, which is a redesigned lightweight replacement emulsion tube and slide needle for the CV and offers improved throttle response. Another alternative, but by no means the last one, is the Yost Power Tube: a selection of jets and the Power Tube itself, it’s designed to eliminate flat spots and otherwise get the best out of your carburation.


Screamin Eagle / Mikuni Carburetor


You could get yourself a Mikuni HSR-42, or a Screamin’ Eagle 44mm CV – FYI Screamin’ Eagle sell a 42mm slide carb which is made by Mikuni -both carbs are for, let’s be frank, competition use, but if you’re going to stick the big bore CV on you then have to think about a a 44mm manifold to bolt it onto. A street-legal 44mm CV is also available for 2001-on Twin Cams and possibly points the way to future legislation.

Talking injection now, you’re pretty much stuck with the factory fittings and of course you could grab yourself an aftermarket part but be prepared for a bit of a battle if you have to claim on the warranty because there are a number of mechanical things that the fuel mix can affect.

Exhausts are just as intricite. Slip-on mufflers are by far the easiest, but a full system will deliver more in terms of a decent upgrade but that is a whole new discussion on it’s own. One thing is for certain is that the balance pipes will remain in place if you just fit mufflers, while aftermarket systems will often lose them.

Balance pipes break up the lines of the V-twin on Sportsters and FXRs but are generally there to reduce noise, reducing the speed of the exhaust gas by allowing it to dissipate before it exits the muffler, but there are many people who blame them for poor performance. The “hidden” low-level balance pipes on Dynas and the new Sportster mean they will stay in place for longer, as they don’t detract from the appearance, but there are increasing numbers of people who are leaning towards 2-into-1 systems like Vance and Hines, Supertrapps or Thunderheaders, and they don’t come much more balanced than both pots exiting the same silencer.

And that’s the main stuff, but not everything because there are a few other things you can do without taking a spanner to the cases, and they are the bits that light the fuel – and a good thing to do if you’ve gone to the trouble of fixing the carb.

Buell Sportster

Stage 3: Thunderstorm heads and V&H pipe hint at something more than a stock Sportster, but the blueprinted crank and balanced Buell top end are hidden.

As you’d expect, Screamin’ Eagle offer a range of ignition systems, both street legal and “competition” which better match the spark to the less restricted motor, while Crane’s Hi-4 and Dyna’s Dyna2000 remain popular choices for those less concerned by their warranties, and have an element of tunability built in so you can experiment. And if you’re going to play with ignition modules, why not coils? And why not plug leads?

All of which falls within the remit of a Stage One.

There’s nothing in there that a reasonably competent home mechanic can’t tackle, but if your bike is still within its warranty period, you’d be best advised to talk to your dealer and make sure they’re not going to suck hard through their teeth when you bring it back, having made a mess.

What sort of mess can you make?

HT LeadsToo weak a fuel mix if you’re playing with the carb, injection module or air filter, so keep an eye on your spark plugs afterwards and make sure they’re the right colour. Getting an air-leak in the system if you mess about with the carb or manifold, which will make it pop under load and on the overrun, and ultimately could blow the rear pot. Getting the ignition timing wrong if you’ve got a fully adjustable unit that will let you play beyond your expertise, in which case it will run badly. Shearing or stripping something by overtightening it, so get a torque wrench or be cautious … no, get a torque wrench: it’s potentially more dangerous for something that hasn’t been tightened up enough to fall off than it is to shear it. Rounding off a perfectly good nut or bolt by using the metric spanners from a previous bike, or your dad’s old imperial spanners, so get decent tools before you start.

Simple stuff really, but be aware that your dealer would rather do the job for you and charge you for the privilege – but also that you’ve got some comeback if they mess up. Also be aware that the fitting of anything non-Harley to your warrantied bike might cause a raised eyebrow, and that even Screamin’ Eagle kit is no guarantee of your warranty surviving intact.

While mentioning that Stage Ones don’t need to have a spanner laid on the engine, it doesn’t actually mean that a Stage One can’t have a Technical: Harley-Davidson Staging spanner laid on its engine, and a Stage One 1550 is actually quite possible. Rebore the original barrels, and drop a pair of the 1550 pistons in under the stock heads and hey-presto! You’ve got a Stage One 1550cc. You can leave the cams alone, although you wouldn’t get the full benefit until you did look at the cams and that would be…

To see an overview of Harley-Davidson staging please click here otherwise click here to see our Harley-Davidson stage 2 article

Stage Two

Now you’re motoring, but now you’re more likely to need the assistance of a professional.

First thing to do is to carry out all the “Stage One” stuff that you want to do before you start, because they are the basis for the next round of modifications: there’s no point sticking hot cams in a strangled motor. By the same token, there’s no point getting carried away with the need for a Stage Two if you’ve not taken your bike to Stage One yet – you might be quite happy at first base.

Stage Two is largely about cams. You’ve got the means to draw fuel into the motor already, and to get the gases out. This is about how long you open the door to let the fuel through, and how wide you open it, and that is determined by what sort of work you want your bike to do.

There is probably more written on Harley Cams that anything else, and there is no shortage of people far better qualified than I to go through the absolute specifics so I’m just going through the general stuff … that way I can’t be blamed for your sticking a wholly unsuitable cam into your motor. What’s unsuitable? Something that makes your bike worse for the way you want to use it.

It is almost at odds with the perception of tuning that you can have a Stage Two motor that is actually detuned compared to the original but then tuning isn’t only about power, it’s about suitability for the purpose. You could make a touring Buell, a hot rod Electra or a lazy T-Sport by judicious use of cam profiles, matched to an efficient induction/exhaust system.

There is nothing especially clever about the principle of a camshaft, and all it does is transfer a rotary motion, which the crank delivers into a pushing action, that you need to open the valves.

A perfectly round shaft spins at half the speed of the crankshaft, driven by gears in the case of Sportsters and pre Twin Cam big twins, and a chain on the stock Twin Cam. On that shaft is one “lobe” per valve and as the shaft spins, anything that follows the track round the shaft and up over the lobe will rise and fall with it. That ‘anything’ is a cam follower, and it faithfully follows the track of the cam’s lobe, climbing the opening ramp, and pushing a pushrod up to a rocker shaft. The rocker shaft rocks when it’s pushed, pushing down onto the top of a valve, which is held in the closed position by heavyduty springs. Springs move on demand, whereas the lobe on the cam is immutable, so the valve opens and stay open for as long as the lobe on the cam is holding it there, but as soon as it rotates beyond that point the spring pushes the valve closed again, rocks the rocker arm, which pushes the pushrod down quicker than gravity would force it to drop and the cam follower rolls down the closing ramp for another circuit before the opening ramp comes round again.

A couple of quick things. The cam spins at half the speed of the crank because it only needs to do something every fourth cycle in a four stroke engine. A classic 2-stroke doesn’t have a camshaft spinning at the same speed as the crank because it doesn’t have a camshaft at all. And cam followers are the quaint old English term for what we now refer to as lifters: almost the same logic in the naming department as lifters lift, but then they also drop. They are also sometimes called tappets, probably because badly adjusted ones make a tapping sound, I guess.

S&S Cycle 551 Gear Drive Easy Start Cams Complete KitCams are specified by lift, duration and angle … and quantity: Sportsters and Buells have four with a lobe apiece, one for each valve, big twins up to and including the Evo had one with four lobes that run all four valves, and Twin Cams have two with a pair of lobes each, one per cylinder.

There is actually a fourth quotient, and that is the ramp. A steep ramp will take the pushrod to the maximum lift very quickly, and return it to rest as quickly as the spring can force it – as opposed to a gentle ramp which the cam follower will … well, follow.

A high lift cam will let more fuel through but they are generally used on fast spinning motors – the high lift allowing a good lungful of fuel and air compensating for the need for a short duration to give the valve chance to close again and be seated correctly before the next cycle starts. You don’t want to compress the fuel while the inlet port is open, because it’ll spit it back out again. If you’re playing with high lift cams, you’re more likely to use stronger valve springs to get the valve shut quickly, but there is a trade-off in that the harder the spring is pushing against the valve-train, the greater the potential for wear of the cam, follower and any bearings.

ABOVE: Stage 1: Spot the Stage One – you can almost hear those cannons from here.

ABOVE: Stage 1: Spot the Stage One – you can almost hear those cannons from here.

A long duration cam will give the maximum amount of opportunity for the fuel/exhaust to get in or out, but shutting the valve late increases the chance of the valve being open on the compression cycle. Better suited to slower-spinning motors in conjunction with a lower lift.

The angle will determine when the valve starts to open, and there can be an overlap built in according to what the engine is to do. It is possible to open the inlet port a little before the piston has reached TDC to make sure that it has opened sufficiently when it starts to descend, drawing fuel through; it gets away with it because the exhaust port is wide open and provides the easier route through. Similarly the exhaust valve won’t quite have had time to shut before the piston descends, but by then the inlet valve will be wide open and it will draw it through there rather than the exhaust valve that is slamming closed.

You will be delighted to know that you haven’t got to make your own decision on any of those elements, as every combination will have been tried repeatedly by very bright engineers. The resulting profiles represent everything from radical to realistic, wild to mild, and are well known for their characteristics. Hopefully you’ll have a better appreciation of why the engineer who knows about these things is asking you lots of questions – and if they’re not, be concerned: they may be good, but they’re not psychic and they need to know what you want.

If you want to play a greater part, you might want to consider the technology of the follower/lifter/tappet. Back in the old days of British pushrod twins, the cam followers were little more than hardened steel metal blocks that slid on the hardened camshaft lobes on a thin film of clean oil; they had a means at the top to locate a pushrod, and a means of adjustment. Meanwhile, Harley have used roller bearings to track the lobes for generations, and housed them at the bottom of their lifters. Not just ordinary lifters either, they’ve used hydraulic lifters since the end of the Knuckleheads: high technology at the heart of the big twin, but the fashion for decades was to replace them with solids. But times have changed.

The valve train of the Twin Cam motor hasn't changed much since the first OHV motor. This shows the lifters, lifter blockslifter locks, and pushrod (left) and the rocker arm assembly (above).

The valve train of the Twin Cam motor hasn’t changed much since the first OHV motor. This shows the lifters, lifter blockslifter locks, and pushrod (left) and the rocker arm assembly (above).

The Twin Cam is so named because it has twin cams. No kidding. In stock trim, these are chain-driven from the end of the crank and are mounted in their own subassembly.

The Twin Cam is so named because it has twin cams. No kidding. In stock trim, these are chain-driven from the end of the crank and are mounted in their own subassembly.

Hydraulic lifters are self-adjusting, using clean engine oil to fill a chamber within the lifter body and a piston that provide the base for the pushrod. The size of the chamber is determined by the valve train itself, and the slack built into it. With the chamber full of oil, the lifter takes up the available slack and acts as a single unit of exactly the right size. But so does a screw thread, I hear you cry. Ah, true, but here’s the rub. An engine is made of metal and gets hot, and metal expands when it gets hot. So as you run your motor the hot bits expand and the cylinder head actually moves further way from the camshaft. How far can a motor grow? Not far but enough to make a difference. Try .040” on an Evo motor, when your valve clearances should be somewhere nearer to .002. With hydraulic lifters, as the engine gets hotter, and the gaps increase, more oil fills the bigger chamber and the slack is taken up.

It’s the opposite of your recollections, if your recollections are of old Brits, because the expansion of the pushrod is greater than the barrels, so Brit bikes rattle when they’re cold, and Harleys rattle when they’re hot – or they do if they’ve got solid lifters.

There is a downside, there always is. Hydraulic tappets are much more complex, and susceptible to dirty oil, and fall down as an engineering principle when the lifter becomes worn and oil can escape from the chamber because it screws up the adjustment.

For all their sophistication, mechanically adept luddites and power junkies missed the simplicity and economy of “solids” and they converted back, backed up by experience of failed units in days when engineering tolerances weren’t as fine as today, but for the majority of owners a set of hydraulic lifters were always better than a badly adjusted set of manual tappets.

Today there are a massive number of engineering companies offering a vast array of hydraulics, semihydraulic and solid lifters for your Twin Cam, Evo, Shovel or Panhead. It will come as no surprise either to note that you can also get high performance lifter blocks to house them, and these are not to be confused with cosmetic covers: if you’re going to seek the finest engineering tolerances in your lifters, you’re advised to make sure they’re sliding in a block engineered to the same standards.

While you’re in the motor playing with cams, it’s as well to replace the stock cam bearing with a better one, but aside from that – and the original Stage One mods – you’re about there. You might want to consider a different ignition module – but you should perhaps have accounted for that when you did the Stage One, giving yourself some elbow-room for further development.

You’ll note from Harley’s Parts and Accessories catalogue that 1550cc motors rear their heads quickly when talking about Stage Two, but that’s not a pre-requisite. Yes, a 1550cc big-bore would be nice, a 1700cc stroker would be nicer but that isn’t necessarily a Stage Two. It could be, but if you’re going to those lengths, it’s worth contemplating a little porting and checking of the rest of the lump, which takes us to …

To read an overview of Harley-Davidson staging please click here or click here to read more about Harley-Davidson stage 1 otherwise click here to see our Harley-Davidson stage 3 article

Stage Three

S&S Cycle Super Stock Cylinder Head KitThere are those who would say that the first thing you should do to make a Harley work properly is to sort out the heads, but that is generally where “Stage Three” comes in.

The combustion chamber on Harley V-twins has benefited from better gas flow characteristics with every evolution, but the standard porting is not best suited to high performance. Porting is a subject in itself, and will be dealt with in the near future by someone who knows what he’s talking about, but we have reached the point where you’re really not going to sit in a shed with a bastard file and an heirloom toolkit. If you’ve got a fully equipped workshop – and we are talking fully equipped here, with lathes, milling machines and a space heater – you’ll know much more than I do already, and I’m amazed you’re still here.

This is where the engineers come in, and you have to put yourself in their hands. Sure, you can buy heads etc and stick them on yourself, but when you’re that deep in, you’re not going to put those heads in without seriously considering what you want from the bike. Well, if you’ve got any sense you’re not.

You’re in big money country now and a half-cocked Stage Three will be not much better than an amateur Stage Two – certainly not worth the additional expense of the parts. Yes, I know you can get ported heads off the shelf, but ported for what? More torque or more horsepower? Higher or lower revs? Fuel efficiency or straight line ability? Before you start you need to know where the power is needed, and what sort of power, to determine the size and shape of the valves: until then it’s merely a technical exercise.

And it’s not just heads, and that is why we now start to differentiate between engineers and fitters. A Stage Three motor really should be a blueprinted engine. It’s no longer enough that it is as good as an assembly line can make it, if you’re going to do it properly, it’s got to be as accurate as the original drawings: the blueprints. If the drawing has a dimension of 1.7701mm that’s what it has got to be, not +/- .005mm. Production lines don’t do that, fitters can’t do that, mechanics would love the time to learn that. The only people who can do that properly are engineers – and even then, only the better engineers. The bad news is that there aren’t many left because there are few coming up through the ranks, and that’s because production lines have rendered a lot of basic skills obsolete and machine minders fill their steel-toecapped boots in industry.

A blueprinted engine will be less stressed than a production line example – even a good production line example – because everything will work as it should: as it was designed to do. The sort of engineer who will be capable of matching the specification will be more than capable of sorting out your porting, cam and carb requirements to make it better than the blueprint for your specific application, and that is the ultimate state of tune for your bike. Harley-Davidson produce motorcycles for the masses, an engineer will make a motorcycle for you … assuming you know what you want, and can communicate that to your chosen professional.

Stage Four

Anything goes. Turbos, blowers, nitrous, strokers, billet motors, massive motors built for the purpose from parts that have never seen Auntie Janet’s bar and shield logo.

Quite bizarrely, a Stage Three bike would be the better bike in the vast majority of cases, and when compared to some of the bikes that drop into the Stage Four category, is likely to be quicker for longer in road use because there’s no guarantee that it’ll be hand assembled to the same standard as a Stage Three. That said, you could always get a Stage Four engine and get it blueprinted it to make it better still – unless you’re 100% certain of the ability of the original builder and you’d be foolish not to entrust to an engineer who you did trust implicitly.

It doesn’t get any more sensible when you consider that it is perfectly possible to bolt an off-the-shelf turbocharger to a stock motor, in which case it’s a Stage Four instantly. Stock cams and stock carb (on at least one option) with just the turbo’s plenum and convoluted plumbing to drive the compressor replacing the air-filter and exhaust. The only thing it has in common with the more serious hardware is the power output, which can be twice that of the stock motor: torque and horsepower. Oh yes, and cost. Stage Four doesn’t come cheap.

A turbo can work out at £3,500, and an engine can cost twice that before you open it up and fettle it some more – and it would be a strange horsepower junkie who could leave the cylinder head in place once they’d unpacked the motor … or the barrels.

And it’s worth a quick look at the crank while we’re down that far.

And it’d be silly not to weigh the pistons seeing as they’re out.

And is that a slight lip on the inlet tract … ? Pass me the emery …

Stage Four is the domain of the serious power addicts. Doubling the stock horsepower isn’t a challenge any more, trebling it would be good though. You won’t see many of these bikes on the road because they’ll have sacrificed a lot of their rideability along the way – in fact some will be physically unrideable – but on a quarter mile strip of tarmac, head-to head with someone who thinks they know better, they will demonstrate just how much you can get out of an air-cooled v-twin motorcycle.

The sad truth, though, is that yesterday’s Stage Four will be thrashed by tomorrow’s Stage Two, and the day after’s Stage One. Performance is transient, even in Harley circles.

There’s something you need to know: no matter what you’ve got it’ll never be enough.

There is some irony in that a lot of people are discovering Harleys today after years of buying faster and faster sportsbikes in search of the thrill they remember when they first started riding … only to discover that riding was more about freedom than speed, which maybe explains the sheer number of stock bikes out there today.

To read an overview of Harley-Davidson staging please click here or click here to return to our Harley-Davidson stage 3 article (stage 2 & stage 1 are here)

With thanks to  Andy Hornsby of American-V magazine from which parts of this article have reproduced . Originally published 22/1/2004 © American-V magazine 

The Hogfather Online

Part of The Hogfather Group

Leave a Reply