Manual Decomp Start - Stupid Question?

3 replies to this topic
  • Guest_blatham489_*

Posted July 15, 2004 - 12:49 AM


Just a thought, someone please analyze it. If the autodecomp works by keeping the exhaust valve open very slightly until the engine fires (reaching the required RPM to allow the valve to close) why couldn't you simply adjust the manual decomp lever to just barely open the valve the same amount as the auto device, and then manually hold the lever while kick-starting, releasing as soon as it fires off? :thumbsup:

  • BigLou

Posted July 15, 2004 - 02:31 AM


I'm pretty sure the auto decomp only opens an exhaust valve for a short duration, roughly around TDC. Similar to how the manual decomp is used-just to break over past TDC. This allows time for *some* compression when kicking, needed to fire the mixture. That's the scenario as I picture it in my head, anyway!

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  • don319

Posted July 15, 2004 - 10:16 AM


When you pull in the decomp lever, you are holding open an exhaust valve so you can push the piston ever so slightly past tdc, then you let go, closing the valve. THEN you kick and the cylinder fires on the way down and starts. Doing what you said will burn the exhaust valve seat and ruin the valve/head. It probably wouldn't start either.

  • John_H

Posted July 15, 2004 - 09:05 PM


just do the correct mod and reap the benefit :thumbsup: :devil: :awww: :lol: :D :lol:

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