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MC Mod performance point of reference

Lacking a real dyno, my "seat of the pants" experience says that adding the KLX needle is the only mod I've made that had a noticable effect on the performance of my KLR. (See my signature for a disclosure of the mods on the bike.)

That said, after more than a few years, it seems to me that my KLR is approaching the perceived performance level of the Ducati 996 I once had. The KLR gets to 45 smartly (although needing 3 gear changes as opposed to no gear changes on the 996 and 70 on the KLR is just as scary as 100+ on the 996.

Would I ever do the MC Mod to go faster? Sure, after all it is "free". (If I ever get around to checking the valves that is.)
 

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Sure, why not? Even if the mystery of the mechanism cannot be explained.

Please post before-and-after top speeds.
You mean real numbers? Naw, as any accountant will tell you, the numbers can be misleading. Too many factors can influence top speed numbers like final gearing, head winds, windshields and clothing (ask Rollie Free about the effects of clothing on top speed).

I prefer to use unsubstantiated impressions to express KLR performance changes. Because there are no "mechanisms" to explain. For example last year my KLR became sluggish. A couple of rides on a smaller displacement bike restored the performance of my KLR for "free".
 

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The MC Mod has been dyno-tested on the Gen 2 bike and the reported gain is on the the order of 7-10%.

The dyno chart that was provided had no real data on it other than the observed maximums for power and torque. There were no numbers on the chart's axis, but I tried to work out what the maximum increase in power was.

That increase appears to be at about 4200 rpm and appears to be 2 hp. Note that the max hp returns to stock at at the peak, so this is a mid-range gain.

The stock hp at 4200 appears to be ~23 hp; the 2 hp gain at this rpm is a gain of 8%. Again, I'm analyzing lines drawn on a picture to interpolate data, not actual data. No actual data for the increase was provided. That data would be a tabular data sheet showing multiple runs of both stock and modified so that an average could be taken and so that one could be assured that this was not an anomaly or a minimum stock run vs a maximum modified run.

The valve timing for the Gen 2 is different from the valve timing of the Gen 1. This mod was not dyno-tested on a Gen 1. The reports on how well it works on the Gen 1 range from "Totally awesome; I powered away from my buddy!" to "My bike didn't run very good afterward. I put it back".

Since I don't understand how it works on the Gen 2, I can't even begin to guess at why the reports are so varied on the Gen 1, though I suspect it has something to do with the Emperor and his new clothes...

Tom
 

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Food for thought,
The MC Mod advances the Exhaust Cam shaft. The Exhaust Cam Shaft has the Kawasaki Automatic Compression Release (KACR) attached to the R.H. end.

If for NO Other Reason, owners of reluctant Cold Weather/Cold Morning starting 2008 and NEWER KLR650's, Should Consider This Mod!

Case in point, '09 oil burning KLR650 29,435 miles. 88 PSI, Cold Cranking Compression.

Recent Schnitz 685cc rebuild, with valve seats as 'Perfect' as I could justify. OEM gaskets, not the oil leaking 'Hi-Compression' Cometic Gaskets.
MC Modded, (exhaust cam advancement), Freshly assembled per Schnitz Instructions, (As in, I can't believe how DRY they want this thing!) NOT Yet Started (Wednesday 4-29-15)! 124 PSI.

Started instantly! As in, was at TDC compression stroke. 2 full rotations of the engine, 4 Cycles! Down on the 'dead' power stroke, Up on a wasted Exhaust stroke, Down on the Intake stroke (full carb, on full 'choke'), UP on the Compression stroke and Running!

Rode it a 100 miles Thursday evening and changed the oil and filter.
Hi ... sure started good... and sounded great. Hi to Tom S. also ..... mike
 

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Randall_64,

Hi Mike!

good to see you here!

Tom
 

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Greg Frasier called me a week ago. Asked me to schedule a valve tappet inspection/adjustment for Tuesday the 25th. OK.

Job done. Opened both exhaust valves 1 shim size. Intakes too close to max. to adjust further open. I did a before and after COLD compression test. 68 psi, before. 76 psi, after.

After paying for the service, he starts inquiring about the MC mod, (Exhaust Camshaft Advancement) have I heard about it???

We discuss things in as much detail as I know.
Might could have gained 10-15 psi Cold Cranking Pressure for easier cold starting. (He says, I don't ride in the cold anymore! And it starts fine.)
Running Compression stays the same, 87 octane gas still OK.
A little more get-up and go. Smoother running, maybe?
Might confuse an un-informed mechanic.

He said, "I guess, stock is Good Enough. It is in every service Manual."

Sometimes 'stock is best'! Greg is looking towards a 6th trip around the World! On multiple bikes, different bike every time he and friend have to cross an Ocean! I'm guessing, 'soft luggage' only!
 

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Men of good will have dyno-tested the MC mod and called it good. But . . . good within the accuracy/precision/repeatability error budget of the dynamometer? (Perhaps so; just askin'!)

Yet . . . advancing the exhaust cam one sprocket tooth SUBTRACTS 15 crankshaft degrees of VALVE OVERLAP. (Question: What is valve overlap? Valve overlap is the angular duration when BOTH intake and exhaust valves are simultaneously open.)

OVERLAP is found more prominently on high-performance engines; in fact, the primary cause of "loping," when a hot rod or drag racer engine idles . . . the PURPOSE of valve overlap is to allow dynamic flow of intake and exhaust gasses, "scavenging" the combustion chamber during high-output operation.

Typically, "performance" camshafts have GREATER valve overlap than stock ones.

Thus, one might ask . . . how does the MC mod, reducing valve overlap, produce MORE power, when practice, experience, and conventional wisdom does not support such cause-and-effect?

Mind you, I'm NOT saying advancing your exhaust cam one sprocket gear tooth will not deliver 10 % more power from idle to redline, as some claim. I only wonder . . . HOW is this performance increase achieved?

Automobiles with "variable valve timing" typically advance BOTH intake and exhaust lobes (on a single stick cam) with rpm, to achieve higher power output at higher rpm operation; however . . . VALVE OVERLAP is not changed, it remains the same under all operating conditions (unlike the KLR650 case, where overlap is reduced when the exhaust cam is advanced).

Thus, another technically inexplicable phenomenon, encountered on the way toward super-tuning and enhancing the power output of the KLR650 engine . . .
 

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MC MOD (alleged)Hooey

I'm amazed that the KLR world I slow to this idea and yet other bikes have enjoyed this little trick for years. Before 4-cycle improvements were the years of perfecting the 'expansion chamber' in 2-cycle bikes. The concept of riding 'on-the-pipe' was born and there you have it. This is largely an exhaust improvement that doesn't translate well to dynos or 4-cycle power and torque. Remember the best power doesn't insure winning the race when useable torque is really what we're after.

While some can't figure out why less valve overlap is more 'power' I give you this borrowed gem of an explanation:

"Exhaust Scavenging and Energy Waves
Inertial scavenging and wave scavenging are different phenomena but both impact exhaust system efficiency and affect one another. Scavenging is simply gas extraction. These two scavenging effects are directly influenced by pipe diameter, length, shape and the thermal properties of the pipe material (stainless, mild steel, thermal coatings, etc.). When the exhaust valve opens, two things immediately happen. An energy wave, or pulse, is created from the rapidly expanding combustion gases. The wave enters the exhaust pipe traveling outward at a nominal speed of 1,300 - 1,700 feet per second (this speed varies depending on engine design, modifications, etc., and is therefore stated as a "nominal" velocity). This wave is pure energy, similar to a shock wave from an explosion. Simultaneous with the energy wave, the spent combustion gases also enter the exhaust pipe and travel outward more slowly at 150 - 300 feet per second nominal (maximum power is usually made with gas velocities between 240 and 300 feet per second). Since the energy wave is moving about 5 times faster than the exhaust gases, it will get where it is going faster than the gases. When the outbound energy wave encounters a lower pressure area such as a second or larger diameter section of pipe, the muffler or the ambient atmosphere, a reversion wave (a reversed or mirrored wave) is reflected back toward the exhaust valve without significant loss of velocity.

The reversion wave moves back toward the exhaust valve on a collision course with the exiting gases whereupon they pass through one another, with some energy loss and turbulence, and continue in their respective directions. What happens when that reversion wave arrives at the exhaust valve depends on whether the valve is still open or closed. This is a critical moment in the exhaust cycle because the reversion wave can be beneficial or detrimental to exhaust flow, depending upon its arrival time at the exhaust valve. If the exhaust valve is closed when the reversion wave arrives, the wave is again reflected toward the exhaust outlet and eventually dissipates its energy in this back and forth motion. If the exhaust valve is open when the wave arrives, its effect upon exhaust gas flow depends on which part of the wave is hitting the open exhaust valve.

A wave is comprised of two alternating and opposing pressures. In one part of the wave cycle, the gas molecules are compressed. In the other part of the wave, the gas molecules are rarefied. Therefore, each wave contains a compression area (node) of higher pressure and a rarefaction area (anti-node) of lower pressure. An exhaust pipe of the proper length (for a specific RPM range) will place the waves anti-node at the exhaust valve at the proper time for it's lower pressure to help fill the combustion chamber with fresh incoming charge and to extract spent gases from the chamber. This is wave scavenging or "wave tuning".

From these cyclical engine events, one can deduce that the beneficial part of a rapidly traveling reversion wave can only be present at an exhaust port during portions of the powerband since it's relative arrival time changes with RPM. This makes it difficult to tune an exhaust system to take advantage of reversion waves which is why there are various anti-reversion devices designed to improve performance. These anti-reversion devices are designed to weaken and disrupt the detrimental reversion waves (when the wave's higher-pressure node impedes scavenging and intake draw-through). Specifically designed performance baffles can be extremely effective, as well as heads with D shaped ports. Unlike reversion waves that have no mass, exhaust gases do have mass. Since they are in motion, they also have inertia (or "momentum") as they travel outward at their comparatively slow velocity of 150 - 300 feet per second. When the gases move outward as a gas column through the exhaust pipe, a decreasing pressure area is created in the pipe behind them. It may help to think of this lower pressure area as a partial vacuum and one can visualize the vacuous lower pressure "pulling" residual exhaust gases from the combustion chamber and exhaust port. It can also help pull fresh air/fuel charge into the combustion chamber. This is inertial scavenging and it has a major effect upon engine power at low-to-mid range RPM.

There are other factors that further complicate the behavior of exhaust gases. Wave harmonics, wave amplification and wave cancellation effects also play into the scheme of exhaust events. The interaction of all these variables is so abstractly complex that it is difficult to fully grasp. There does not appear to be any absolute formula that will produce the perfect exhaust design. Even super-computer designed exhaust systems must undergo dyno, track, and street testing to determine the necessary configuration for the desired results. Last but not least, the correct choices and combinations of carburetor, air cleaner, cam shaft, ignition, and exhaust used in the proper relationship to each other for the intended riding application will always produce the finest quality results. Most important of all, is to do your research prior to purchasing the combination of products and equipment best suited to your individual style of riding."

By the way...lookout for my upcoming patented variable backpressure exhaust system coming to the KLR world soon. wink wink.

With no variable valves, ecu/efi and a host of other improvements, what are we gonna do with this venerable lug.
 

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Interesting, roadapple!

However, I do not glean information specifying, opening and closing the exhaust valve earlier during the cycle, reducing valve overlap, enhances the cylinder-scavenging fluid dynamics across the entire rpm spectrum.

The information may be there, but I'm to dense to grasp it.

One question: Which bikes have profited from reducing valve overlap?
 

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Gen 1 and 2 KLR 650s.
Exclusive of KLRs, Drifter.

Here's the comment I addressed: "I'm amazed that the KLR world [is] slow to this idea and yet other bikes have enjoyed this little trick for years."

WHICH "other bikes" have enjoyed this little trick (reducing valve overlap) for years?

Regardless, do you know how reducing valve overlap increases power output? As mentioned, every "performance" cam I ever heard of had overlap exceeding that of the stock cam profile. Maybe Iskenderian, Web Cam, Hot Cams, etc., are all in error.

How do you think the MC mod produces additional power, Drifter?
 

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Two more cents (for what it's worth)

I believe that advancing the KLR exhaust cam timing and thereby reducing the intake and exhaust valve overlap is just moving power down to a lower RPM range. Greater overlap does increase power but usually at a higher RPM. Great for racing when we are holding the throttle wide open and revving the engine to the max in every gear. But for street an trail, a fatter mid and low range power band is more noticeable and usable.
 

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Makes perfectly good sense, twinjet: More conservative valve timing (reducing overlap) characteristically delivers greater torque and power at lower rpm. However . . . the fans of the MC mod claim increased power across the entire rpm spectrum, from idle to redline.

This claim may be valid; I only wonder, how?
 

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Makes perfectly good sense, twinjet: More conservative valve timing (reducing overlap) characteristically delivers greater torque and power at lower rpm. However . . . the fans of the MC mod claim increased power across the entire rpm spectrum, from idle to redline.

This claim may be valid; I only wonder, how?
Compared to most bikes, the KLR650 has a very wide power band and so the power band can be moved down with little or no perceived loss in top end power. Unlike a narrow power band "race" tuned bike where moving the power band down would cause a noticeable loss in top end power.

"Seat of the pants" dynos are somewhat inaccurate when called upon to measure small changes in power at specific RPMs.
 

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"Seat of the pants" dynos are somewhat inaccurate when called upon to measure small changes in power at specific RPMs.
Good point; any loss in top-end power from reducing overlap might go undetected in the "seat-of-the-pants" dyno's precision error budget! :)
 

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You just put your words into what I said. Solenoid driven, independent titanium valves, direct injection, exup servos, secondary butterflies, even VVT, they are going to blow your mind.

Yet people somehow do this mod on their KLR's and enjoy it. They see improvements in their particular RPM range. Some put it back after taking a hit to fuel economy, or having some starting problems. Some even make special exhaust cam gear mods to make the advance even less than one tooth.

Checkout other Hondas or early model Kawasaki Concours before 2008. Thumpers, 2-cylinder, in-line fours. Somebody did it there too. Air cooled Ducatis benefit from critical use of the degree wheel and adjusting that thing called valve overlap to their particular benefit.


Check out Wikipedia and tell them they're wrong. Or pick on the Shovelhead crowd; they're an easy mark.
 

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Oh boy....... I think I'll jump in here and send this heavy discussion into another direction.

Emission control.
The good old EPA mandates that certain emission levels must be met, and the levels change every year for cars & trucks. Bikes are on the horizon for testing, and have to meet certain standards now for US sales. It'll be another way for the states to test and charge you some stupid amount of money to stick a sniffer up your bikes pipe and say NOPE!

Some cars still have a wonderful little device called an EGR valve. (Exhaust Gas Recirculation)
Back in the 70's most manufacturers put these on every engine. (and retard the timing) By pulling a little exhaust gas back into the intake, the already burnt gas took up space in the combustion chamber "cooling" it by being an inert gas in the mix. This also reduced the dreaded "Oxides of Nitrogen" or better known as NOX. NOX is the stuff that put the hole in the ozone layer supposedly. An old trick was to remove the EGR valve, and block the port so everything going into the cylinder was air/fuel mixture, or put a BB in the vacuum hose, or make a sheet metal shim to block off the port...we by-passed everything because smog stuff was stupid back then. Then came EGR "manual operation tests" in the smog tests where you had to lift the valve manually and hear a stumble. Then on to sensors that turned on the check engine lights when the EGR valve didn't work, computer controlled EGR valves, and on, and on...
Computer controls opened up a lot of possibilities for timing, injection, cam timing, solenoids, etc. to decrease emissions. Some great engineer figured out that if there was the proper amount of "overlap", some of the exhaust gasses would remain in the cylinder and act as that cooling inert gas without an EGR valve.
Get rid of the EGR valves, save money on parts, one less thing that people can't bypass, less weight, ..... You get the idea.
The cams are ground with a little overlap that produce the same effect as an EGR valve, change the cam timing, and return to a more pure air/fuel ratio in the combustion chamber. Thus, a little more power.

I've done it, it helped, and when working with 37 horse power, everything helps.

I love the video where the guy says that the "tuners" do all this stuff and it doesn't run right. Because Ford, GM, Honda, Toyota, Nissan, Rover, Renault, BMW, Mercedes, Yamaha, and Kawasaki have spent millions on reducing emissions, and improving mileage.
And then a bunch of guys in an on-line forum can re-engineer an over grown lawn mower engine by a hit-n-miss approach to getting more power.
And I'm one of them.

Just my .02 cents worth, and I didn't want to piss anybody off with all the other GREAT (not sarcastic) posts on overlap. Cam timing has so many facets to it, and a good engine builder will always want to see the cam profile when ordering a cam for a certain type of engine.
(disclaimer- my California smog license expired in 2003 after a career as a mechanic)

But above all? Keep riding out there. Explore the great world we live in, find that side road, that back road, that dirt road that you haven't been down yet, and EXPLORE.
That's what the KLR was designed to do.


And now........... I think I'll go get a nice adult beverage to enjoy.
 

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First, roadapple, seems to me you mis-characterize my remarks: I never said anyone (even Wikipedia) was, "wrong." Instead, I have sought an explanation of how reducing KLR650 valve overlap produces additional power across the entire rpm spectrum, from idle to redline.

Regrets if this question offends, and/or is judged inappropriate.

The video clip you imbed suggests valve overlap is a worthwhile parameter in engine operating dynamics; I ask: How does a reduction in valve overlap generate additional power from idle to redline (as some claim)?

Checkout other Hondas or early model Kawasaki Concours before 2008. Thumpers, 2-cylinder, in-line fours. Somebody did it there too. Air cooled Ducatis benefit from critical use of the degree wheel and adjusting that thing called valve overlap to their particular benefit.
You have the advantage, roadapple; I'm unfamiliar with those engines, how and how much valve overlap was reduced, and the magnitude of the additional power gained from the process. As well as, whether the gains occurred at some particular rpm regime, or, as with the KLR MC mod, across the board.
Check out Wikipedia and tell them they're wrong. Or pick on the Shovelhead crowd; they're an easy mark.
As mentioned, I've not suggested anyone is "wrong." I have no quarrel with anything I know of Wikipedia asserts regarding valve overlap, nor have I any motive to educate the Shovelhead crowd, even if they're in error, as you suggest! :)

Increasing power output by reducing valve overlap may appear contrary to conventional wisdom regarding aftermarket "performance" camshaft profiles. I only ask, how does the MC mod produce additional power at all engine rpm regimes.

I salute with great respect those who have experimented in this area, conscientious souls of high integrity as far as I know. I only ask, "How does it work?"
 

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First, roadapple, seems to me you mis-characterize my remarks: I never said anyone (even Wikipedia) was, "wrong." Instead, I have sought an explanation of how reducing KLR650 valve overlap produces additional power across the entire rpm spectrum, from idle to redline.
Damocles,
From what I remember from the .net posting by Eagle Mike and Mike Coe (MC mod), the additional power 'signs off' at about 6200 rpm! Not redline (7500 rpm).

As to how? I'll only suggest that it allows a 'longer Draw' of fresh intake mixture at the lower RPM's.
 
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