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Discussion Starter #1
Anyone done this, if so tell us what you think? Do you like the change if any, would you do it again? How many miles with the mod do you have? Dyno info seems hard to come by so i guess seat of the pants will do.
 

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Type that excact title, or "free power" in the search box,
and a buncha stuff will pop up. There's a whole KLR library here.
Been researching and thinking on this one myself.
 

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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.
 

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Discussion Starter #4
I have read allot of posts from several people who have done this mod and nearly all really liked it and noticed the change...7-10% torque and HP. When i check my valves i am going to do this mod! :)
 

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Drifter,
Can we ask you, to do a Before and After, Cold Cranking Compression measurement?

How is your cold starting? At what altitude? At what minimum Temps?
All in the interest of KLR science, of course!

Yes, we all appreciate a 'broader' power spread! But we have got to be able to Start It, at 28f. in Silverton, CO at 9800 ft. in August, to enjoy IT. Or, maybe start it at -32f., in the NW territories, on the 'Ice Roads", in March!
 

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I have read allot of posts from several people who have done this mod and nearly all really liked it and noticed the change...7-10% torque and HP. When i check my valves i am going to do this mod! :)
The "MC Mod" reduces valve overlap by 15 crankshaft degrees.

Torque and horsepower increased 7-10 % from idle to redline?

Fantastic. FANTASTIC!

Men of good will doubtless have performed credible dynamometer runs confirming this performance increase; would like to see some charts (beyond the accuracy/precision/repeatability error budget of the dyno) . Besides before-and-after dyno runs, maybe some before-and-after quarter-mile timing tickets?

If this promise of "free power" is valid, then . . . REJOICE! For all generations?

The power increase claimed is not unlike that claimed from the "PCV Valve Mod," also scantily documented. Yet, "perception is reality" with many mods. Nothing against the MC Mod, only wonder--how does reducing valve overlap INCREASE peak power; the reverse is true, regarding conventional valve timing.
 

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Discussion Starter #7
OK, i will do a compression test, it wont be anytime soon few months at least!

I live 131 ft above sea level and its Hot in the summer, sometimes in the winter also, 9000 ft. is nose bleed altitude for me! The way my bike is jetted it would not run at 9k feet! Maybe that is why you have starting problems?

The PCV mod to me seems the wrong thing to do, the pcv creates a vacuum in the crankcase on the upstroke of the piston which would reduce power just like having no vent which would create excess pressure In my opinion the small hole in the airbox is to create a neutral air exchange in the crankcase? This is one mod i am not doing.
 

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OK, i will do a compression test, it wont be anytime soon few months at least!

I live 131 ft above sea level and its Hot in the summer, sometimes in the winter also, 9000 ft. is nose bleed altitude for me! The way my bike is jetted it would not run at 9k feet! Maybe that is why you have starting problems?
Drifter,
My personal bike, 1987 -A1, starts fine, runs fine between 4000-13,800 ft, +25 to 95 f.. Might be a tad lean on the mid-range needle at 105f., <4500 ft., but I really didn't like the KLX650 needle, at least on my bike.

My cold cranking compression hoovers in the 100-120 psi range, with tappet adjustments every 10,000 miles. Can't remember it's leak-down reading. CRS!
 

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The PCV mod to me seems the wrong thing to do, the pcv creates a vacuum in the crankcase on the upstroke of the piston which would reduce power just like having no vent which would create excess pressure In my opinion the small hole in the airbox is to create a neutral air exchange in the crankcase? This is one mod i am not doing.
Any QUESTIONING of the efficacy of the PCV Valve Mod can get a poster BANNED from one or more motorcycle forums, Drifter! Be very careful about where you express any doubts! :)

Eschewing the PCV Valve Mod, you deny yourself not only the increased power allegedly available, but also the claimed additional fuel mileage, lower oil consumption, enhanced engine compression braking, and improved ring seating.

The MC Mod may indeed be a valid improvement; I simply cannot understand how the increased power is produced, given the sacrifice of 15 crankshaft degrees of valve overlap . . . cut that's jus ME! :)
 

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Food for thought,
,,,,,,,,,,, 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!
This little snip-it of information makes me wonder.
"Why couldn't Tom Schmitz and others kick-start their '08 and newer models after spending the time and money to convert?"

I had witnesses/spectators to the ease of start-up.

Maybe this statement belongs in the kick-starter thread?
 

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Discussion Starter #11
I can see how the pcv could cause better ring seating and braking with the engine because the vacuum created by the pcv, better gas mileage and less oil burning...seems it would be the opposite making the engine work harder and pulling more oil up on the cylinder wall. Maybe the valve timing is enough to to eliminate the vacuum created, if so that would end the better ring sealing which was the purpose of the mod to start with. After seeing that small hole in the airbox where the vent hose is connected caused me to rethink this mod and the reason Kaw did it this way. Maybe it works for some oil burning engines? Give it a try tell us how it works for your bike.

Some things you do not question. How long before i get banned here?
 

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I can see how the pcv could cause better ring seating and braking with the engine because the vacuum created by the pcv, better gas mileage and less oil burning...seems it would be the opposite making the engine work harder and pulling more oil up on the cylinder wall. Maybe the valve timing is enough to to eliminate the vacuum created, if so that would end the better ring sealing which was the purpose of the mod to start with. After seeing that small hole in the airbox where the vent hose is connected caused me to rethink this mod and the reason Kaw did it this way. Maybe it works for some oil burning engines? Give it a try tell us how it works for your bike.

Some things you do not question. How long before i get banned here?
Actually, Drifter, in actual tests, no vacuum has ever been measured in the crankcase of a KLR650 engine with PCV Mod installed; whether spring-and-ball valve or vane-type, no vacuum. Rather, an over-pressure (compared to atmospheric) exists in the running engine's crankcase . . .

Nevertheless, the operational enhancements mentioned (i.e., more power, better fuel mileage, lower oil consumption, improved engine compression braking, enhanced ring sealing) have been reported by users firmly convinced of these benefits.

I think the reasons Kawasaki "did it this way" (i.e., valveless vent hose to atmospheric pressure side of air box) was: 1. Engine as-built passes current emission standards, and 2. Intake backfire dynamics adequately managed by baffle arrangement (a major function of a "real" PCV valve in an automobile is preventing intake backfire flame from entering crankcase, where combustible mixture may exist). DISCLAIMER: Conjecture on my part; don't know why Kawasaki, "did it this way!"

Fear not banning for expressing your opinions, generally, on this website; or . . . even for questioning concepts . . . depending somewhat, perhaps, on the mood/attitude of the moderator poised over the banning button! :)
 

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...Some things you do not question. How long before i get banned here?
Yer gonna have to try real hard to get banned here.

Generally we just love a good discussion.

Some of us will question everything that doesn't have a logical explanation, doesn't pass the sniff test, or will, at the very least, make for a good argument. Some of us want to understand 'how' and 'why'. 'It just works' is fine, but what do you learn if you can't understand the how and the why?

The sort of conversations that you'll find here are the sort of conversations you'd find around a friendly campfire. Anything and everything is fair game for discussion as long as it stays the way you'd do it in meat-space. If you think that something you'd say in meat-space would get your ass kicked there, it'll happen here. If not, not.

Aside from spammers and porners, I think we've banned mebbe three or four people in the past few years. That says a lot about the caliber of people on this forum. Gentlemen and scholars, all.

Tom
 

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Damocles,
I dis-agree about the crankcase venting the "the atmospheric side of the air box".

The atmospheric side is the Dirty side!

I'll suggest there is a 'slight' vacuum in the clean side of the air box when ever the engine is running.

I thought we had discussed it to end over here, http://www.klrforum.com/klr-other-motorcycle-related-discussion/25618-dissertation-ventilation.html
Would it be fair to say, "vented to essentially atmospheric pressure in the air box?"

The point; NOT vented to manifold vacuum, as with a "true" positive crankcase ventilation system, as found on automobiles.

(We'll discuss the metering system used by automobile PCV setups on another thread! :) )
 

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Would it be fair to say, "vented to essentially atmospheric pressure in the air box?"

The point; NOT vented to manifold vacuum, as with a "true" positive crankcase ventilation system, as found on automobiles.

(We'll discuss the metering system used by automobile PCV setups on another thread! :) )
Sounds appropriately correct.
 

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Discussion Starter #17
I do not understand how a vacuum is not created on the upstroke of the piston if the ring blow by and downward movement of the piston creates pressure?

If the vent is open in stock configuration, i think 14.7 lbs of pressure is a constant in the box i can see how that might eliminate the vacuum, with a pcv there would be no pressure to equalize the crankcase? What fills that empty sealed space?

Use a small fish tank pump as an example, each cycle one side sucks air the other blows air. For every action there is an opposite and equal reaction. :)

I think Tom is referring to you guys, i do not fit his description.....:35a:
 

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Hypothetically speaking, say you had an engine without a vented crankcase and the combustion chamber was open to the atmosphere. If you spun the crankshaft the pressure in the case would rise when the piston went down and drop almost equally when it went up. Leakage past the rings would cause the case pressure to be less than what the swept volume of piston would calculate to. But because the leakage would be equal in both directions (combustion chamber open to the atmosphere for discussion sake) there would be no vacuum or pressure gain in the case.

A running engine without a case vent will build pressure in it's case because the pressure of the power stroke will force more leakage past the rings into the case than the lower case pressure can force back on the down stroke of the intake stroke.

The KLR's small vent orifice relieves enough of that pressure to prevent problems but is not really big enough to vent the case. (Ever wonder why the oil gets so dirty so fast?)
 

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I do not understand how a vacuum is not created on the upstroke of the piston if the ring blow by and downward movement of the piston creates pressure?
The "vacuum" may be immediately negated by the pressure of the downward piston stroke . . . and further compromised by piston blow-by . . . were there vacuum to be retained, the PCV valve would have to open and close at TWICE the rate of the engine valves, perhaps a daunting mechanical task for a passive PCV or check valve, even a vane-type . . . regardless, as previously mentioned, in actual tests, no durable "vacuum" has ever been recorded in the crankcase of a running KLR650 engine, even with the PCV Valve Mod, even with a VANE-TYPE check-valve installed.

Said tests were reported on .net; instrumentation consisted of a manifold vacuum/fuel pump pressure gauge teed into the crankcase vent line. With no durable static vacuum measured (except during extreme and brief deceleration), hard to account for all the claimed advantages of the PCV Valve Mod, IMHO. Durable crankcase vacuum doesn't appear to be available, thus hardly responsible for the improvements.

Regardless, more power to those who enjoy the PCV Valve Mod's benefits.
 

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Not going back to stock timing

Mean while back to the subject of MC mod. I hold tec days in Arizona and assist at other tec days in Flagstaff. The Flagstaff TD we have Eagle Mike and his bag of tricks, Dooheckys, KLX needles, Thermobobs and all the rest.

We do valve adjust and MC mods. I have done MC mods on a dozen or more 1st and 2nd Gen bike. So far no one has changed back to stock timing. That's the great thing about this mod. If for some reason you don't like more low end torque and power. You can change it back with no harm.

Eagle Mike has done the dyno testing. He was going to market a cam advance gear. Found that your not going to do much better then the 7.5 degrees jump of one tooth on the exhaust. So he past this on as free power. The problem with this is people screw it up. They advance one tooth on the crank, giving a 15 degree advance on both cams. Retard instead of advancing. There's a lot of room for error.

All I can say is try it. It's not that much work. If your savvy enough to do your own valve adjustment. You should be able to turn the exhaust cam one tooth counter clock wise. I know I'm not going back to stock timing on my 2013. :mexican wave:

:t1204: You may now go back to the previous off topic descussion.
 
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