KTM 640 Adventure Oil Issue


I need some advice on my old 640A; when I sustain higher speeds/RPM, I lose motor oil from the breather hose “snorkel” located under the right side of my seat. This leaves oil on my factory tool kit, chaingaurd and the right side of my swingarm. Assuming that this is normal, does anyone know of a clever fix to prevent this oil loss? A 17 tooth sproket really wouldn’t help because that would just encourage me to go faster with the same RPM oil-loss issue.

Mike Gray 5 years 11 Answers 1204 views 0

Answers ( 11 )

  1. You’re building too much crank case pressure from compression leaking by the piston rings that’s pushing the oil out of the breather vents. Low speeds and low throttle settings isn’t bad yet, but the high RPM’s and speeds is. Basically, your motor is worn out.

    • That would sound about right if it wasn’t a 660 motor that I just built with a new Wössner piston & rings, new valves, guides & seats, cylinder bored and Nikasil’s at Millennium along with the new 660 Rallye crank and con rod, bearings et al.

    • Hmm. The symptoms you describe usually are due to compression leaking by the rings called blow by.

  2. I see that guy is everywhere. So do you have the foam inserted in said hose?
    numero quatro

    • As many times as I’ve pulled this hose off, I’ve never looked inside it! And as many times as I’ve poured over KTM schematics, I’ve never paid attention to number four! I’ll pull the tank first thing in the morning to inspectthat breather hose; Thanks Michael!

    • NP.. if you dont want to order just the OEM you can use reticulated foam they use inside of gas tanks to stop sloshing..

    • Good to know! I may have some hidden in my shop from my Lotus Seven’s fuel cell. Otherwise I’ll add #4 to my latest parts order.

    • you may still get a bit but not enough to soak your filter or anything. It oils your chain when your going really fast is the way I look at it..

    • Great, I’ll just get a longer snorkel tube and position the tip right over the chain. lol

  3. For what it’s worth, I don’t see any oil if I stay under 75-80mph but 100 for extended periods (5+ miles) leaves oil on the tool kit behind the right side number plate and eventually the swingarm. With the stock gearing I’m revving just over 7k which isn’t too close to the factory “red line” of 8.5k.

    A big THANK YOU! to Gaynore for sharing his wealth of LC4 knowledge including the solution for my 640’s self-oiling chain issue! You were spot on suggesting that my valve cover’s breather tube might be missing its in-line “snot-catcher.” I’ll order that filter KTM part #5843008900 this week. Thank you again!

  4. NP.. now what oil are you running….lol

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