piston orientation

[raczekp1]

hi.
I'm trying to rebuilt Johnson Evinrude 4.5 hp, 1980.
i forgot piston orientation in cylinder bore.
how to determinate which side i should put into?
maybe someone can explain how to figure out piston sides(which side goes to exhaust and which to suck port)

 

[racerone]

Re: piston orientation

The sloping side goes to the exhaust.----The " steep " deflector side goes to the intake ports.-----------Not sure what you mean by the " suck " port.----There is no suction there.--The fresh fuel comes in because of pressure in the crankcase !

 

[Bosunsmate]

Re: piston orientation

yep steep side faces suck side so the fuel air entering hits it and goes to the top of the cylinder which helps push the exhaust down and out the other side. Unfortunately it pushes a bit too much so you always get a bit of unburnt fuel $$$$ going right through unused especially at idle

 

[F_R]

Re: piston orientation

Universal rule of any crossflow two-stroke engine with domed pistons.

 

[raczekp1]

Re: piston orientation

thamks so much for explenation.
best to all of you

 

[gm280]

Re: piston orientation

thamks so much for explenation.
best to all of you

Not sure about your engine, but I think if you put the pistons in 180 out, the head won't fit back on it...

 

[boobie]

Re: piston orientation

On some motors they will work and others not. If you do get them to work backwards you'll get one hell of a rpm drop at WOT. Been there.