Internal layout 1986 V6 200HP 2stroke crankcase????

Yamahahaha

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Dec 24, 2011
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If there is someone who knows I would very much appreciate information on the actual layout design of the crankcase for a 1986 200HP 2-stroke Yam V6 with reed valve sets: Is the crankcase comprised of just one common chamber or are there individual sealed crankcase chambers for each of the 6 cylinders - I am thinking there are 6 individual chambers to create the right vacuum for each cylinder but would like to know before I remove the carburettors etc to check the condition of the reed valves - It may have direct relevance to the problem I am currently experiencing.
Cheers,
 

99yam40

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Sep 7, 2008
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Re: Internal layout 1986 V6 200HP 2stroke crankcase????

they are sealed individual chambers.
 

Silvertip

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Sep 22, 2003
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28,771
Re: Internal layout 1986 V6 200HP 2stroke crankcase????

And on a two stroke the crankcase goes both ways -- pressure and vacuum. Vacuum draws fuel in during the upstroke. Pressure sends the mixture through the bypass ports during the down stroke.
 

Yamahahaha

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Dec 24, 2011
Messages
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Re: Internal layout 1986 V6 200HP 2stroke crankcase????

Thanks. I understand about the 2-way function but was not sure if they were individual chambers. If the reed valves are broken in any one or more of the reed valve sets would this (a) affect compression in the relevant cylinder? (b) Result in limited fuel mix getting into the combustion chamber?
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Internal layout 1986 V6 200HP 2stroke crankcase????

Thanks. I understand about the 2-way function but was not sure if they were individual chambers. If the reed valves are broken in any one or more of the reed valve sets would this (a) affect compression in the relevant cylinder? (b) Result in limited fuel mix getting into the combustion chamber?

It will affect idle quality and perhaps some high end but it will not compression. Compression occurs on the upstroke when the ports are covered by the piston so the reeds are not a consideration.
 
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