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Old 05-07-2014, 09:45 PM   #1
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Country: England
Location: Just North of Pompey
Occupation: Procurement manager
Interests: Boats and Bikes
Boat name: The Nashers Revenge!
Boat make: Ocean 6.25
Engines: Suzi-wong 200HP EFI
Cruising area: Solent

Join Date: Dec 2004
Location: Just North of Pompey
Posts: 132
2 stroke Crankshaft oil seal orientation.

Hi all.

Canít believe Iím asking this as Iíve built quite as few 2-stroke powerheads up in the past, but have been thinking about this so much Iím now doubting myself.

Iím in the middle of putting the younger Nashers DT15 back together from the pile of parts I brought and am about to drop the crank assembly into the block.
I donít have a proper manual, just a parts explosion that doesnít show enough detail to help.
I didnít take it apart either so didnít see the old ones in position.

Obviously normally with an oil seal the cup or open ĎUí side points towards the inside of engine where the additional pressure helps the seal open up against the shaft itís sealing.

With a 2-stroke it doesnít work that way when itís sucking in mixture, but on a 2-stroke bike youíd normally still point the open bit inwards.

Iím convinced that other 2-stroke outboards Iíve put together have the top seal with the ĎUí pointing inwards but the bottom one pointing out, ie with the powerhead in position both open cups point downwards.
Probably because the exhaust is at a higher pressure on the outside of the lower one.

Can anyone confirm Iím right?


Heaven doesn't want me, and Hell is afraid I'll take over
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