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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.
Thanks for the clarification (less power at higher rpm); I seem to remember claims of 10 % additional power throughout the rpm spectrum.

As to the "longer draw," hard to visualize when the exhaust valves close earlier in the cycle, but indeed: Could certainly be the case.
 

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Discussion Starter #62 (Edited)
Ok, i adjusted my valves this past weekend, 3 were tight both exhaust, they were only .005 after getting the 3 tight ones set to factory spec i advanced the cam 1 tooth installed a new plug and put it back together. Bike has 10k miles.

Here are my impressions of the mod.
1. I noticed the idle speed jumped about 250 RPM.
2. It will pull with light throttle at 1500 rpm now, about like 2200 before.
3. It sounds better and feels different and smoother.
4. I do notice a bit more power.
5. The throttle feel is a bit more abrupt at low RPM
6. The bike starts at least 50% quicker than before.

I had my idle set at 1k RPM before and after the mod, so i took a ride liking the results. I did notice closing throttle quickly the bike died several times even coming to a nomal stop. So i changed the idle speed to about 1250 and the problem went away. The engine does have less flywheel effect on closed throttle and takes longer to slow while in gear.

In conclusion, i like the mod and do notice the change in power the sound is deeper at idle and running, way better coasting in gear the 2k to 5k change is most noticable me. Hats off to MC!

I would not do the mod unless the valves needed checked but while there do the mod. Next valve check the cam advance will remain as is advanced. The future will tell if gas mileage changes.
 

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Congratulatins, Drifter!

Thanks for sharing your personal experience and perceptions.

Any idea HOW the MC mod produced the improvements you experienced?
 

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Discussion Starter #64
No, my brain is to old and filled with other more important stuff...to figure it out or care at this point. I had my doubts also that is why i waited till i did the valve adjustment to try it, It is not a great change but to me it is worth the small effort required. If my gas mileage stays the same or improves i will be a really happy camper.

All this being said the lighter flywheel effect is a negative for me what i mean by this is the revs drop quicker during shifts or when snapping throttle shut that is why i was having the stalling issue with the idle speed at 1k the engine would drop to about 800 or so for a split second, i guess my bike wont idle that low even for a splt second, setting the idle at 1250 the engine drops to about 1k then very quickly returns to the set idle speed. This will take time to adapt to, slightly quicker shifts are required to be as smooth as before the mod , these are the only negatives i have noticed the positive improvements out weigh these for me. :character00201:

Next time you do your valves give it a try.
 

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Been thinking about it, next time I have the bike dynoed! :)
Damocles,
Are you going to 'Pay' for 2 dyno runs?
A before 'modification', base line run and an after modification run?
Did you just get an "inheritance check"? ;)
 

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It would surely seem logical that the outcome could be fairly easily predicted with all of the computer programs out there. It ain't me man. Also, the baseline should already be quite well established, as many KLR's there are out in the world.

Or like usual, am I off base
 

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Fatheroftwo,
I was just 'jerking' Damocles chain, 'so to speak'! Merry Christmas!

I have spent more on 3 Laboratory Oil Analysis's than I have on the actual Oil CHANGE's! All in the interest of better "KLR Science" of course.

With Normk's finding of 'idle rpm' change, with simple crankshaft oil flow reduction or NOT, I'm considering 'spending the money'!

The local Harley performance shop, 'Strokers, USA' does have a dyno! I might have to 'Pay Extra' for a Jap bike. They will NOT even change a tire on a H,K,S or Y bike!!!!!!
 

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Dang old Harley snobs.

I'll poke my nose back in where it belongs.
I plan on spending a lot more time here, as I have a new 2013 KLR, and want to spice it up a little once the warranty runs out.
 

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Adding a 'Thermo-Bob' or EM 'Dohickey' should Not adversely affect your warranty. Provided, that they are installed 'correctly'.
But I do understand your concern.
 

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Actually . . . I have proposed before-and-after dyno runs, evaluating popular modifications (22-cent, MC, and PCV Valve, for instance) to a prominent publication, with sufficient budget to fund the tests.

Some interest in the project (they have a Generation 2 KLR650 in their stable for evaluation).

Just curious; anecdotal and seat-of-the-pants evaluations abound; wondering what quantifiable, repeatable measurements might say.

Yet . . . any "delta" (change) in performance might be swept up in the dynamometer's accuracy/precision/repeatability error budget, rendering the testing meaningless. Sometimes, though, meaningless is fun!
 

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That would sure take out some guess work, and expose "the emperor" that has no clothes, or boost sales of the mods that work as advertised. I'll stay tuned, as I would like to unleash some of the stifled power locked away in my KLR.
 

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I did this mod on a bone stock 09 KLR 650, it makes a big difference in power, seems to rev faster as well. Never dyno'd, but it pulls really well up and down NC/SC hills. No drop in feul economy either, still get better than 60 mpg if I stay off the interstate. 16t front/42t rear sprockets.
 

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I did this mod on a bone stock 09 KLR 650, it makes a big difference in power, seems to rev faster as well. Never dyno'd, but it pulls really well up and down NC/SC hills. No drop in feul economy either, still get better than 60 mpg if I stay off the interstate. 16t front/42t rear sprockets.
Welcome to the forum 'Surfersami',
Were you running the 16/42 combo prior to the MC mod?
 

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When I did this mod, I was running a 15/42 setup. Even so the difference was quite noticeable. The engine revs easier, it pulls strong across the whole rev range, and it seems to crank easier. Some of this could also be that I did the valve adjustment at the same time, the valves were tight, but not out of spec.
I am running the 16/42 combination now, and I am never wanting for more power, and I still get better than 58 mpg. I do not ride hard. I feel there is enough difference that if I got another KLR I would do the mod again.
 

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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?
Digging up bones here.lol

I'm not very smart, but i'll take a stab at this question. Though my answer won't really be an answer, but more of a continuation of the question...if that makes sense.

1-Yes, most racing type cam profiles use increased overlap. Not because they want to, buy because they have to. No matter what we change, there will always be 360 degrees in a circle, so that can not be changed for a camshaft which rotates in a circle.

2- Racing type cams use longer durations of valve opening for one reason: lift.
Higher lift gets the valve further away from it's seat, so that port can breathe easier. Increasing lift somewhat forces duration to increase by default. You have to slowly open and close the valves, just can't just slam them open and closed without eventual damage...so, in order to open and close the valves softly you end up with a longer duration of time from opening to closing the valve.

When you increase duration you can't help but to increase overlap, to a degree. You are forced to do it, but everyone knows that increased duration/overlap also opens up the door to losing cylinder pressure.

Everyone also knows and agrees that compression is power. When overlap increases, dynamic compression suffers. This is why drag motors lope. They suck at idle. The engine isn't happy, it can't idle smoothly, vacuum is low, throttle response is poor. This is why stall converters exist ( torque converters for auto trans that don't engage until higher in the rpm range). The car needs to "pass over" the lower rpms where it runs poorly and reach the higher rpms where is runs well. Cam builders know all about this and do their best to defeat it, but like mentioned before, there are physical restrictions to what is possible with only 360 degrees available.

One option is very aggressive cam lobe profiles. Kick the valve open quickly, let it breathe, slam it back shut...all in the least amount of time ( duration/ overlap) as possible. You can get a engine with increased low/midrange this way, but valvetrain life suffers every single time.

So is increased duration/overlap more power? Depends on how you define power. Do you want a large peak horsepower number, or do you want a broad range of usable torque?

Horsepower doesn't exist. Horsepower is a mathematic equation based on torque and time. Only torque really exists/can be actually measured. Torque is king and what you can actually feel.

When you port heads, install larger carbs, open exhausts, air boxes, etc...you are allowing additional air to be available to the engine. How the engine uses that air to produce power depends totally on the profile of the camshaft. Highlift+ long duration/overlap= good upper rpm breathing that will give up some torque down low for the gain of upper rpm breathing... or what's known as horsepower.

Now, if your cam has just enough lift to allow the head to breathe and the cam profile is designed to trap the absolute maximum amount of compression as possible ( low duration/ low overlap) then there is more air/fuel charge still present when the compression stroke takes place. This is gonna give you great low rpm torque, but you are not going to force that engine to rev very high, so you are not going to produce a lot of 'horsepower", but you are going to feel a lot of "power".

Diesel engine are perfect to illustrate this. Massive compression numbers, huge torque numbers, low horsepower numbers, low rpms...but they produce awesome "power".

Two things are a given for making power: displacement and compression. Take any engine of any combination and give it either, or both, of those two and power will rise across all rpm areas. No other modifications can do this ( except forced induction, which is nothing but artificial displacement and compression anyway, so it kinda proves the point). All other mods will give power in one rpm range and steal it from the another area. Physical limitations of circles and rotating internal combustion engines. Period.


So...can the MC Mod produce more low rpm torque by limiting valve overlap? In theory, yes, I believe so. The cam profiles are unchanged, so lift, valvetrain life and cylinder filling abilities are unchanged, only the event of when the valves are being opened are changing. Changing valve events is Cam Profile 101 for determining the attitude a motor will have ( torquey vs sreamer). Increased lift and duration is just chasing a HP noumber.

It seems obvious that this MC Mod IS trapping more cylinder pressure due the complaints of hard starting. That's pure compression, which is where pure torque comes from. Will it give up upper rpm power? According to the dyno charts it doesn't. Why? Maybe because the KLR has a dopey cylinder head/ exhaust system that is already hindering upper rpm power ( we know it does), so any "losses" there are already being masked by other variables, so all you end up feeling is an increase in cylinder pressure/ more compression/ more torque when operating in the lower rpm ranges.

I think this is 100% plausible. The theory matches everything people already agree on when it comes to valve timing. Is it pure luck that this change of one tooth just so happens to allow the valve timing event to occur at a more efficient time? Maybe. But I think this also proves something else about these motors that we already know: they are extremely basic. A finely tuned motor typically responds in large ways ( either good or bad) to changes like this. The fact that these engine can kinda absorb changes like this with very small, of any, effets is a good indicator that there is a huge amount of untapped capability here. But for a twin cam, 650cc engine that makes 45-ish hp at the crank...we already knew that.

I haven't looked at much of the thread over at .net. The dyno charts were cryptic at best, so nothing to really learn over there. The main thing I would be interested in hearing is accounts from trustworthy people who tried this mod. I see what Jeff posted about it and had hope, then I saw what Tom posted and got back on the fence. :grin2:

I also noticed something here that Paul posted. He adjusted the valves for a customers bike and gained compression back by putting the engine in to a healthy state of tune again. Totally awesome that you measured that btw. That is just as good as dyno proof IMO. I see lots of guys posting "I'll try this when I go to adjust my valves"...perhaps the increase in torque/compression/ power they are feeling is not actually the changing of the cam timing...but rather just a result of reclaiming lost compression the engine already had??? Who knows...I sure don't.

Has anyone really felt an improvement from this that didn't also adjust valves while in there?
 

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Excellent effort to "prove" a foregone conclusion, shinyribs! :)

I'll gently critique your treatise shortly!

Meanwhile, could I interest you in the PCV Valve Mod? :)
 

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Meanwhile, could I interest you in the PCV Valve Mod? :)



And no need to be gentle. lol. I think the biggest reason I love drag racing was actually just trying different engine combinations. I learned that what is considered too small, old fashioned, too heavy was generally the same parts we could get the most power from. I love the theories on stuff like this. It's one of the few things I can sometimes wrap my head around ( diagnosed with learning disabilities at a young age), so I kinda thrive on it. Always open to be told I'm wrong ( often am) and learn new things.
 
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