1998 Valkyrie horsepower gains???

[Carter716]

I’m going to have my valkyrie torn down to make some alterations to the stock setup and was wondering if there is a way to increase horsepower without taking away from the reliability of my engine? I was looking into the superchargers, but they are not easy to find and have heard they will blow the motor over time. Any suggestions and input would be greatly appreciated!!!   Thanks, Clayton.

[MarkT]

Changing the exhaust to a 6 into 2 adds scavenging and if you also get rid of the huge backpressure from the mufflers that stops wasting that parasitic drag.  A flow-thru exhaust like glasspacks does that and bonus sounds great, deep & rumbly, louder but not a lot. Has no effect on reliability of the bike and makes around 8 ponies, torque around same number, as always YMMV. I just happen to build such exhausts and have several extras you can add if you're inclined.  My ad rotates above but I'm at http://www.horseapple.com/Valkyrie/Valk_Products/M2W_Exhaust__System/m2w_exhaust__system.html as a shortcut.

There's a few other such small mods, others will pipe up on.  Like the IS ECM; some like the trigger wheel mod particularly the 4° one, or the similar electric advance mod. Have Attic Rat do his magic, or Big BF tune your bike to a T.  Some mods not so useful, like polishing the intake runners.  Some claim results on the butt dyno but it didn't help my Deerslayer - result reports vary. The desmog and K&N filter mods just improve maintenance tasks - no help on power. Serious power gains happen by spending $$$.  Like Attic Rat's port & polish, shave heads and flycut pistons.  I don't think that affects reliability.  Neither does a blower if you keep the boost at lower levels. Mine is about 7# and output is around 150hp. Trimming weight is always a good thing to increase apparent power.  Not just on the bike, either.  Don't do what I do, do what I SAY.

[hubcapsc]

"me too" posts often aren't helpful, but... what MarkT said.

MarkT, Attic Rat and BigBF are and have been the main
dudes when it comes to tuning a Valkyrie...

-Mike

[Pete]

The real question is how much horsepower can you afford?

Most small inexpensive mods yield small increments in horsepower. And some do none

If you have cubic dollars, then bore it out to minimum wall thickness, replace the pistons/rings, increase compression and open up the exhaust (valves and passages), open up the intake and carbs (valves, passages and carbs), install custom ground high lift/long duration camshafts and higher valve springs so the engine can spin and breath at 8000 to 9000 rpm.

And yes engine life is going to be affected in relation to how high you spin it.
But it will be quick and if you do the work and custom order the parts and machine services $8000 to $10,000 should do it.

[MarkT]

The real question is how much horsepower can you afford?

Most small inexpensive mods yield small increments in horsepower. And some do none

If you have cubic dollars, then bore it out to minimum wall thickness, replace the pistons/rings, increase compression and open up the exhaust (valves and passages), open up the intake and carbs (valves, passages and carbs), install custom ground high lift/long duration camshafts and higher valve springs so the engine can spin and breath at 8000 to 9000 rpm.

And yes engine life is going to be affected in relation to how high you spin it.
But it will be quick and if you do the work and custom order the parts and machine services $8000 to $10,000 should do it.

Lotsa effort to yield "maybe" results and hurt the reliability. Though granted it's fun to tinker and even have the fastest Valk in your town.  Might be better to leave your Valk for cruisin and for go-fast buy a Hyabusa or ZX-14.  Thinkin you could find one under $10k easy.

[gordonv]

Why?

A blower, you're talking real power. Why, racing? I'm just trying to understand why.

My thought was more along the lines of learning how to ride, and I don't mean the basics down the street. I know a guy who wheelies his GW GL1500 & GL1800, down a alley with speed bumps.

I couldn't handle more power, or wouldn't know what to do with it.

VERY good suggestions already made. It's all about the $$$. You want a faster bike, buy one. You want to have the fastest Valk for racing, there are some out there who do it.

[98valk]

the oem head pipes have a too small ID. using larger header 3 into 1 exhaust pipes will provide an instant 10-15HP increase. Then go from there. airbox mods w/jetting, R1 cams or web cams and head work. The OEM exhaust ports are highly restrictive for the Pair valve emission system. mild cleanup increases flow 10 cfm on the exhaust side and 5 cfm on intake. more than enough for the OEM cam valve lift. using web cams for more lift, the heads can be opened up some more.

[Pete]

Real life example from 1977.
Had a 1975 GL1000 (cost new $2350) with a broken oil ring and scratched cylinder and 26,000 miles.

Decided I had to rebuild anyway so why not "enhance it".

Ordered a big bore kit (pistons and rings and wrist pins).
Ordered new high lift, long duration cams.
Bored the block to max.
Ordered new bearings and gaskets.
Open up the exhaust and intake, retuned the carbs.

Cost in excess of $1000, did all the work myself to save the labor. Worked on it off and on for about a week. So figure my labor at  20 to 25 hours, so say another $1000 labor if hired out.

I now have an additional $2000+ invested in a used bike.

The pluses: it was quick and displaced 1100 CC's, it was a sleeper as you could not tell anything had been done, due to the thin cylinder walls it warmed up quick (it did not overheat), it was the fastest GL1000 in this town, it acted and drove like a stock GL1000 until you twisted the grip, gas mileage was still good while cruising.

But I now had about $4500 invested in a used 26000 mile GL1000 worth maybe $1800 on a good day.

Taught me a lesson, buyem, ridem, minimize the mods and add on's to what you really need.

[MarkT]

the oem head pipes have a too small ID. using larger header 3 into 1 exhaust pipes will provide an instant 10-15HP increase. Then go from there. airbox mods w/jetting, R1 cams or web cams and head work. The OEM exhaust ports are highly restrictive for the Pair valve emission system. mild cleanup increases flow 10 cfm on the exhaust side and 5 cfm on intake. more than enough for the OEM cam valve lift. using web cams for more lift, the heads can be opened up some more.

Nope.  I disagree.  The headers are not a bottleneck.  Larger headers alone will not help much if at all. They are matched to the heads, and engineered by Honda.  OEM pipes make more streetable torque by having higher velocity flow through them due to their diameter.  Now if you also do head work - port, polish, valve sizes and higher lift cams, stronger springs to increase flow to match larger diameter headers, and assuming there's enough flow through the carbs to match - make it a balanced, tuned system w/o bottlenecks - then you would see more power.  And of course get rid of the restrictive mufflers, go to open mufflers like glasspacks and change them to 6-2 config instead of 6-6 to add scavenging.

As I said before - the Valk is already a muscle bike, and a dead reliable one at that.  Push it's power output up a lot, and you will likely impact reliability.  Like finding the weak link in a chain.  Been there done that, back in the day with a Chevy deuce coupe.  I think it's smarter to buy a faster bike if that's what you want and don't push the Valk too hard or you will cause breakdowns.  Keep performance mods on the mild side.  Just MHO.

[98valk]

the oem head pipes have a too small ID. using larger header 3 into 1 exhaust pipes will provide an instant 10-15HP increase. Then go from there. airbox mods w/jetting, R1 cams or web cams and head work. The OEM exhaust ports are highly restrictive for the Pair valve emission system. mild cleanup increases flow 10 cfm on the exhaust side and 5 cfm on intake. more than enough for the OEM cam valve lift. using web cams for more lift, the heads can be opened up some more.

Nope.  I disagree.  The headers are not a bottleneck.  Larger headers alone will not help much if at all. They are matched to the heads, and engineered by Honda.  OEM pipes make more streetable torque by having higher velocity flow through them due to their diameter.  Now if you also do head work - port, polish, valve sizes and higher lift cams, stronger springs to increase flow to match larger diameter headers, and assuming there's enough flow through the carbs to match - make it a balanced, tuned system w/o bottlenecks - then you would see more power.  And of course get rid of the restrictive mufflers, go to open mufflers like glasspacks and change them to 6-2 config instead of 6-6 to add scavenging.

As I said before - the Valk is already a muscle bike, and a dead reliable one at that.  Push it's power output up a lot, and you will likely impact reliability.  Like finding the weak link in a chain.  Been there done that, back in the day with a Chevy deuce coupe.  I think it's smarter to buy a faster bike if that's what you want and don't push the Valk too hard or you will cause breakdowns.  Keep performance mods on the mild side.  Just MHO.

sorry most think that however, I've dyno'd with viking headers and oem modified 3 into 1 with glasspacks. Viking upped power everywhere and increased mpg, over my glass pack setup, no additional head work or cams were done. The Viking head pipes are the correct all around size. Remember Andy was a high level champion car racer, the vikings were designed with all of the latest design knowledge at the time. The OEM head pipes are too small, perfectly designed for EPA testing. Also I suggest u read everything David Vizard has written about exhaust systems, and there are others out there that added to his work. Much has been learned since the '60s and '70s.

[MarkT]

I'll have to see the proof before I'll take anyone's word for those claims.  Been there, done the work for too long otherwise.  I know Gale Scalzi (Oz) made radical claims for his son's pipes on this board - but other wrenches including me were suspect of his motives and our results differed and we said so here. The Viking pipes have headers larger than the header ports - so how does that help unless the heads are opened up? ( so do most or all of the aftermarket pipes, since they were singlewall; the inner pipes of the OEM headers LOOK anemically small so they wanted their pipes to look more robust.  Honda engineered them - I believe they knew what they are doing, making the pipes for a street bike. )  It's not a racer, it's a street bike.  You want STREETABLE torque, not gangbusters horsepower with a torque curve that's very pitched.  Do you want the power to come on strong suddenly when you're in the middle of a sweeper and accelerating?  I don't.  I want a flat torque curve. One reason to also NOT have equal-length headers that make gobs of HP high up on the tach but lower down it's much less.  You want the cylinders tuned to be optimum at different speeds, spreading the torque (and hp) curve out, flattening it.

And if his pipes were so good why did his business fold?  I was here years before he started and I'm here now years after he's gone.  And you can't buy those pipes now unless you find a used pair somewhere.  I'm still in production.  Proven product.

[98valk]

I'll have to see the proof before I'll take anyone's word for those claims.  Been there, done the work for too long otherwise.  I know Gale Scalzi (Oz) made radical claims for his son's pipes on this board - but other wrenches including me were suspect of his motives and our results differed and we said so here. The Viking pipes have headers larger than the header ports - so how does that help unless the heads are opened up? ( so do most or all of the aftermarket pipes, since they were singlewall; the inner pipes of the OEM headers LOOK anemically small so they want their pipes to look more robust.  Honda engineered them - I believe they know what they are doing, making the pipes for a street bike. )  It's not a racer. And if his pipes were so good why did his business fold?  I was here years before he started and I'm here now years after he's gone.  And you can't buy those pipes now unless you find a used pair somewhere.  I'm still in production.

Like I said go read and study. One thing to read about is called exhaust port Reversion.
done conversing with u once u start attacking a persons business esp. when u know nothing about their business one of which the pipes where only a small part of the business.

[MarkT]

I do know something about Viking's business I watched them closely and documented what they did.  They made obvious mistakes I won't elaborate here. And you can stop assuming I need to read up on your topics like I know nothing.  Been building exhausts for 18 years now, over 1500 systems.

In the interest of helping readers understand some of the technicals of exhaust systems, and germane to the above arguments, herewith I'm reproducing the text of an "Exhaust 101" tech article from https://www.hotbikeweb.com/custom-motorcycle-exhaust-technical-analysis#page-3   written by Ronnie W. Powell.  Sorry, don't have his bona fides.  I guess I (or you) could google that.

Take a few minutes and read it.  Note, the discussion on pipe diameters and the results on torque and horsepower.  Note also, it explains the same thing I said above, in better terms.  Smaller headers make more torque, especially at lower rpm's, at the expense of high hp at high rpm's.  And produce more scavenging to draw out the exhaust gas and increase the fuel/air charge. And provide quicker throttle response.  Large headers make more hp at higher rpm's at the expense of torque down low. To me, that means the stock headers are more suited to a street bike, while Vikings are better if you are going to race.

The article also explains "scavenging" and "reversion", phenomenons I have been explaining re: my exhaust builds for years.

Quote:

A tuned exhaust system can increase engine power over stock by getting more of the fresh air/fuel mixture into the cylinder. Since the potential power in an engine is determined by the amount of fuel available for combustion, then adding more fuel will increase potential power. The tuned exhaust adds fuel by doing the following: being more efficient in getting the spent gas out of the cylinder, thus creating more room for a fresh charge; and creating a low-pressure area at the exhaust port to help suck in more fresh charge during cam overlap.

Pulses  

To begin our understanding of how the exhaust functions, visualize two pulses traveling down the pipe. Each exhaust stroke produces both a physical pulse of hot, spent gas and a sonic pulse of sound energy waves.

The gas pulse travels down the pipe at approximately 300 feet per second. It goes primarily in one direction-out-until it is dispersed into the atmosphere. Its important attributes are velocity and temperature. It has mass and inertia. The flow of the gas pulse is affected by changes in pipe diameter, length, shape, and thermal properties.

The sonic pulse travels at the speed of sound (between 1,300 and 1,700 feet per second in the hot gas) and easily outraces the gas pulse. The sonic pulse is readily reflected up and down the exhaust system. The reflections are called reversion waves. With velocity constant, its important attributes are amplitude and frequency. It has no mass. The sonic pulse is reflected by a cross-section change in the pipe, such as collectors, mufflers, or the end of the pipe.

As these pulses travel in the exhaust system, each one produces a zone of high pressure before it and a zone of low pressure behind it. Exploiting and controlling these pressure zones is a key component to exhaust turning.

Scavenging

Scavenging is when low pressure in the pipe at the exhaust port helps extract gas from the cylinder. The low-pressure zones in both the gas pulse and the sonic pulse can be used to scavenge, called inertial scavenging and wave scavenging, respectively. Inertial scavenging is strongest when gas-flow velocity is greater. Wave scavenging is most effective when the reflected sonic pulse arrives at the exhaust port while the exhaust valve is open. Sonic waves that arrive when the exhaust valve is closed have no direct impact but do help to prolong the low-pressure zone of the gas pulse for the next exhaust stroke.

Cam or valve overlap is that brief period of time at the end of the exhaust stroke and at the beginning of the intake stroke when the intake and exhaust valves are both open. Scavenging doubles up during this time because the low pressure in the exhaust pipe not only sucks the spent gas out of the cylinder-it also helps suck in more fresh charge through the intake.

The amount of time the valves overlap is a function of engine rpm. Therefore, timing the arrival of reversion waves also becomes a function of engine rpm. Thus, exhaust performance peaks at a specific rpm band. Designers use several techniques to spread performance over a wider rpm range but never maintain maximum (or peak) power from low to high.

Backpressure, Velocity, and VolumeBackpressure is one of the more debated and misunderstood topics concerning exhaust systems. Some say you should eliminate backpressure for a free-flowing system and maximum power, while others say you should keep some backpressure to prevent over-scavenging (drawing fresh air/fuel into the exhaust) and loss of power. Let's define backpressure and see how it impacts the performance of the exhaust.

Backpressure is the resistance in the pipe to the flow of gas. As mentioned earlier, the engine must work to push exhaust gas down the exhaust system. That work is spent overcoming this resistance. Obviously, the greater the backpressure, the more work is required to oppose it, and so the less power is available to move your bike. Conversely, the lower the backpressure, the less work is required to oppose it; therefore, the more power is available to move your bike.

If that was all there was to it, then the free-flowing experts would win, and we'd all have big-diameter, smooth, straight drag pipes.

Ahh, but there's more. There are two reasons to reduce backpressure: to recover the power lost overcoming resistance, and to increase flow velocity. Lowering the backpressure by smoothing the inside of the pipe, by eliminating restrictions, and by removing obstacles not only lowers the resistance to the flow but will also increase flow velocity. Or, if you really want to be precise, lowering the backpressure decreases the rate at which the flow velocity decreases. The gas always slows down because the pipe isn't frictionless; with lower resistance, it just doesn't slow as fast or as much. For our layman's discussion, we'll leave it simple. But then, what has flow velocity got to do with exhaust performance? Everything. And you can't consider flow velocity without also considering flow volume.

A higher flow velocity will produce quicker throttle response and more torque in the low-to-middle-rpm range. Greater velocity increases the high- and low-pressure zones surrounding the gas pulses and thereby improves scavenging. A higher flow volume will produce maximum power in the middle-to-high rpm range. High volume is required at the high end because much more gas must move through the engine. Intuitively, then, we tend to agree with our free-flowing experts again and see that the best exhaust system will minimize backpressure to maximize flow velocity and flow volume. Unfortunately, this is where the compromises and the misunderstandings begin, because the laws of physics say that the same pipe can't do both.

In addition to backpressure, pipe diameter is a major factor in determining both flow velocity and flow volume. Think about blowing through a straw. With a small straw, it's hard to blow, but your breath comes out really fast. With a large straw, it's easier to blow through, but your breath comes out more slowly.

So here's the dilemma. Choose a large-diameter pipe with minimum backpressure and large volume to get tremendous high-rpm power, but the slower flow velocity will rob the low end of torque. The solution to these flow dynamics is to pick a design compromise that offers satisfactory throttle response, torque, and power over the entire rpm range.

As for the debate about the need for backpressure-it's not whether some is needed or not; it's that in the overall design compromise some backpressure is always left. That's misinterpreted as a need for backpressure.

Header-Pipe Construction

Smoother is better. Gas moves like a fluid and will flow better if it's treated to gentle, well-rounded turns and smooth surfaces. Fortunately, most of today's motorcycle manufacturers, unlike auto exhaust makers, have not resorted to the use of low-cost, thin-wall, compression-bent pipe in their stock exhaust. While compression bends are easy to mass-produce, they can collapse or crimp the pipe in the bend, often cutting the exhaust flow in half. The better exhaust systems use mandrel bends, which are made by a pipe-bending machine that uses a noncrushable insert or stiffener (the mandrel) that goes into the pipe while bending to prevent the pipe from becoming crushed.

Pipe diameter impacts both backpressure and flow velocity. It also impacts gas temperature. Exhaust gas is hot, and we'd like to keep it hot. Cold air is denser, and therefore heavier. The heavier the air, the more work the engine does to push it out the pipe. A large exhaust pipe will slow the exhaust flow, giving the gas time to cool. Coating the pipe with an insulating material, such as header wrap or a ceramic thermal coat, also helps keep the gas hot. An added bonus in moving hot gas away as quickly as possible is that it helps cool the cylinder.

A stepped header pipe offers a slight compromise on the small-versus-large-diameter pipe dilemma. The first few inches of the tube are small diameter, which is then mated to a slightly larger-diameter tube. This creates a Venturi effect that maintains high flow velocity at the exhaust port, then allows the higher gas volume to expand farther into the pipe.

Does the length of the exhaust pipe play any part in tuning an exhaust system? Yes, it does. The end of the pipe is a major reflector of the sonic pulse. As the pulse moves down the exhaust and surges into the ambient atmosphere, a reversion wave is created that travels back up the pipe. The length of the pipe is calculated so that the reversion wave arrives back at the exhaust valve before the valve closes, thus allowing the reversion-wave low-pressure zone to aid in scavenging spent gas from the cylinder.

The Muffler

The muffler is a basic component of the exhaust system. Its sole purpose is to silence or muffle engine noise. However, in general, mufflers achieve sound dissipation or absorption at the expense of performance. To make a typical stock engine quiet requires a muffler that has several internal structures that slow and cool the hot exhaust gas and absorb sonic energy. These create restrictions that generate backpressure. To work, mufflers use two similar designs with either a smooth or baffled inner core, along with several techniques for absorption and reflection.

Most high-performance mufflers use a smooth, straight-through inner core. Inside the body of the muffler is a straight pipe perforated with many small holes. Wrapped around this inner pipe is a heat-resistant padding such as stainless-steel mesh, ceramic fibers, or fiberglass wadding. As the exhaust gas passes through this pipe, sound energy enters the holes and is absorbed by the padding. The flow of the gas is unrestricted.

Baffled-inner-core mufflers can have a wrapped, straight pipe inside the body, but instead of small holes the pipe will have louvers that stick down into the exhaust flow. These louvers direct sound energy and exhaust gas into the padding. They also create turbulence to diffuse the sound.

Baffling can also be achieved with inner chambers, which redirect the exhaust flow and reflect the sound energy inside the muffler body. The spacing of the chamber walls is designed to cause similar frequency waves to collide, thus canceling one other. These mufflers may also use absorption materials.

On some exhaust systems, the inner cores, whether smooth or baffled, are removable and the padding replaceable. In addition, some manufacturers offer variable-flow devices, such as adjustable disks, which allow the owner to modify the exhaust characters for sound and performance.

Other stuff

Torque cones, power cones, monster cones, and anti-reversion cones all refer to similarly designed diameter-reduction devices that usually are placed near the exhaust flange to restore low-rpm throttle response, power, and torque on straight drag pipes. Torque cones create a Venturi effect that increases flow velocity as the gas passes through the narrow part of the cone. Anti-reversion cones are designed to diminish and disrupt the negative reversion waves. Step-pipe headers can also act as anti-reversion devices.

Collectors

A collector is unique to two-into-one-design exhausts and refers to the joint where the two header pipes converge. The header pipes must come together in a smooth taper to maintain high gas velocity, while the single exit pipe must be large enough to accommodate the combined gas volume.

A collector generates power in several ways: First, by simulating the end of the exhaust pipe, it can create reversion waves. The timing of those waves depends on how far down the header pipes merger. Second, by interleaving the exhaust pulses, the pressure waves are shared between the two header pipes. This tends to enhance and multiply the effect of each. Next, by creating a Venturi effect as the gas expands into the larger collector, the lower pressure acts to pull gas from the header pipe. Finally, a collector can act as an anti-reversion device to stop unwanted reversion waves from the end of the pipe.

Collectors usually spread performance improvements over a wider rpm range and often create more top-end power. The crossover pipes found on many stock exhausts improve performance much the same as a collector.

Rules of Thumb

No exhaust system delivers maximum peak performance in all applications across the full rpm band. All systems compromise performance in one area to deliver better performance elsewhere.

Since this is a layman's guide, we'll skip the formulas and list a few general rules here:

    Minimize backpressure and maximize flow velocity, then work backward from there.

    Small-diameter pipes increase low-rpm throttle response and torque but choke at high rpm. Conversely, large-diameter pipes increase high-range maximum power but gasp at low rpm.

    Short pipes make more horsepower. Long pipes (of the same diameter) make more torque.

    Collectors, i.e., two-into-one exhausts, are good for widening power across the rpm range. If not collectors, then crossover tubes.

    Loud doesn't make power. And mufflers are good-for your neighbors.

[Blackduck]

Well after that little read you could both be right or is that not wrong?
All systems are a compromise, stock usually for noise control and pollution requirements,
they can be changed to improve performance.
Have a set of full bore headers (maybe Thunder pipes ) and 1 3/4" pipe after the collectors going into 1 3/4" Glass packs, have not lost any noticeable torque at lower RPMs. Would have to troll through my dyno sheets to see if I have before and after runs.
The pipes came with a 4" pipe after the headers that I guess originally came with baffles.
The 4" was open when first installed and I did not lose anything but some of my hearing.