Excessive Blow By?
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Joined: Jan 2018
Posts: 137
From: SW Idaho
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Excessive Blow By?
Folks,
With the passing of 2019, I didn't get anywhere NEAR the amount of riding in that I had hoped. No worries, that tends to happen considering I have 3 youngsters whom I devote much of my free time. In fact, my youngest has developed a passion of riding motorcycles and now he's riding too - a TTR50. Score!
Anyway, a resolution for 2020 is to ride more. And though snow is currently flying in my neck of the woods, I find myself in the garage in the evenings tweaking and wrenching on the bike in anticipation of warmer temperatures.
I started it this past weekend (just to hear it's lovely sound). And while it was idling, I figured I'd take the oil fill cap off to check for blow by - not because I suspected any problems, only because - well, why not. I was actually shocked to discover how much blow there is. I was expecting very little, or maybe just a whisper of air. Instead, it was chugging out of there with force!
So, simple question: is this normal?
Engine runs perfectly, from what I can tell. Plenty of power, no misses, hesitations, or anything of that nature. Doesn't burn any oil. Gets a solid 70mpg average riding. A hair over 2000 miles.
With the passing of 2019, I didn't get anywhere NEAR the amount of riding in that I had hoped. No worries, that tends to happen considering I have 3 youngsters whom I devote much of my free time. In fact, my youngest has developed a passion of riding motorcycles and now he's riding too - a TTR50. Score!
Anyway, a resolution for 2020 is to ride more. And though snow is currently flying in my neck of the woods, I find myself in the garage in the evenings tweaking and wrenching on the bike in anticipation of warmer temperatures.
I started it this past weekend (just to hear it's lovely sound). And while it was idling, I figured I'd take the oil fill cap off to check for blow by - not because I suspected any problems, only because - well, why not. I was actually shocked to discover how much blow there is. I was expecting very little, or maybe just a whisper of air. Instead, it was chugging out of there with force!
So, simple question: is this normal?
Engine runs perfectly, from what I can tell. Plenty of power, no misses, hesitations, or anything of that nature. Doesn't burn any oil. Gets a solid 70mpg average riding. A hair over 2000 miles.
Senior Member
Joined: Sep 2009
Posts: 5,050
From: Abilene, TX
1st Gear Member
Very normal. Single cylinder engines with small crankcase volumes move lots of air while running. Crankcase pressure is an interesting topic even on multicylinder racing engines that operate at high rpm. Big singles like the KLR650 may even have a little bit of oil use because of this issue, but the KLX doesn't have a problem with it.
There's nothing wrong with you KLX unless you're actually seeing blue oil smoke coming out the exhaust, and even then it's more likely due to valve train oil seals or piston ring wear, not crankcase pressure.
Google a topic like crankcase pressure control in racing engines, and you'll see some interesting issues on the subject.
There's nothing wrong with you KLX unless you're actually seeing blue oil smoke coming out the exhaust, and even then it's more likely due to valve train oil seals or piston ring wear, not crankcase pressure.
Google a topic like crankcase pressure control in racing engines, and you'll see some interesting issues on the subject.
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