The "MC Mod" reduces valve overlap by 15 crankshaft degrees.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!
Drifter,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?
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!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.
This little snip-it of information makes me wonder.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!
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 . . .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?
Yer gonna have to try real hard to get banned here....Some things you do not question. How long before i get banned here?
Would it be fair to say, "vented to essentially atmospheric pressure in the air box?"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
Sounds appropriately correct.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! )
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.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?