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Crankcase Pressure

Discussion in 'Motorcycle Tech Talk' started by Too_Old_To_Care, Jun 4, 2008.

  1. Too_Old_To_Care

    Too_Old_To_Care New Member

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    I think I know the answer, but I'll ask anyway: Can the carb support bosses on early 1340 heads be drilled through and tapped to work like breather type heads, using an aftermarket air cleaner kit?

    Thanks
  2. Lucifer

    Lucifer Well-Known Member

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    I'm not sure if you can do that, but may I ask why you are thinking about it? If you don't find the breathing thru the case enuf I'd look for a second hand set of 91 or newer heads and the middle section of the rocker box with the umbrella valves in it before potentially destroying a perfectly good set of heads.
  3. Too_Old_To_Care

    Too_Old_To_Care New Member

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    Thanks. Originally the crankcase vented into the backside of the air cleaner. I've had an aftermarket air cleaner for many years now which necessitated a simple filter on the end of the crankcase vent and I'm just getting tired of cleaning the filter every few months. It's about time to pull the heads anyway, I'll probably wait until then and explore these options.
  4. Art_NJr

    Art_NJr New Member

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    I was going to ask basically the same question Lucifer did 'cause the head-breathers don't work anywhere near as well as a crankcase breather does. I've got both on my 100" engine but I could block the head-breathers off 'cause they really don't do anything - the crankcase setup does it all.
  5. Too_Old_To_Care

    Too_Old_To_Care New Member

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    Hmmm, interesting. I had always assumed the head breather was a better set up. Time to rethink this. Thanks for the info.
  6. hotroadking

    hotroadking Super Moderator Staff Member

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    on an elbruto 113 it was popping the oil cap out constantly on hard runs,

    Even when we ran it down 1/3 to 1/2 qt low - pow!

    Head breathers.

    Motor made too much pressure

    Now it's vented both, crankcase to a small filter hidden behind the trans and a down tube from the heads.

    Don't know if you can drill the heads but you probably could swap to a newer set of heads pretty cheaply.

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