[jbranson]

It's almost always a 360.
But yeah...like both of them dudes say....almost.

360 means that each cylinder fires 360 degrees of rotation from the previous cylinder. Technically all you'd have to do to make them both fire at the same time would be to re-grind the camshaft. Assuming it was a four stroke.
JohnnyB

 

[jbranson]

All Honda 160's, 175's, and CB200 are 360 degree engines. Both pistons go up and down at the same time. However they alternate firing. Left side goes to TDC (compression)..fires....crank rotates one time...right side is at TDC (compression)...fires....crank rotates one time...left side is at TDC (compression).. fires.....etc.

Don't confuse "firing" with ignition....these bikes can use a one dual outlet coil because you can send spark to both cylinders at the same time...only one is at TDC on the compression stroke...so only one fires. A 360 degree twin has combustion every rotation of the crank...that's why they sound like two strokes at 12,000 rpm.

I call these engines "360 Engines" instead of 360 degree cranks...because...with the SAME crank and a different cam you could combust both cylinders at the same time if you wanted....which would be either a 0 degree engine or a 720 degree engine.

Probably the safest way to discuss it is to talk about crankshaft offset....how many degrees one crank journal is offset from the other....if they are on opposite sides of the crank....a 180 degree. If they are on the same side....0 degree or 360 degree....depending on the camshaft.

Can get real complex with more than two cylinders.

JohnnyB

 

[jbranson]

That is kind of curious, wonder why they did it. I've talked to people who have pressed apart 175 cranks and put them back together as a 180 and then had a new cam ground up. They could never find a definative answer on the dyno as to what made more power. Seemingly not enough difference to matter. I prefer the 360 degree on a small bike because it make the ignition system much simplier and lighter.
JohnnyB

 

[jbranson]

Hey...what is an old Yam XS650? They are 360's right?
That was my first brandy new bike...a 77 XS650...loved the way that front wheel moved an inch back and forth at idle.

Bill,
That makes sense....engine could rotate a full turn or so to build up momentum before a compression stroke.

Did the Brits do a "twingle" 360 degree twin at some point? Both pistons up and down at the same time and firing at the same time?
JohnnyB

 

[jbranson]

Mikey,
From all I know you are right on the money. That's why I only do 2-1 exhausts for 360 degree 175 twins.

JohnnyB