Downeaster is correct - the smaller Hondas were 180 deg. twins with one up and one down - but I don’t think that the 1960s-70s CB200-350-360 series engines had counterbalancers.
BTW - the proper terminology for the type of engine used in our XS650s is a four-stroke cycle engine. This means that each complete engine cycle consists of four strokes of the piston:
- a downward stroke to draw in a new charge of air & fuel;
- an upward stroke to compress it;
- a downward stroke when the mixture combusts and provides torque to the crankshaft;
- a final upward stroke to expel the exhaust gases out through the mufflers.
Obviously there is a lot of valve opening/closing action and ignition stuff going on in the background to make everything work properly. Thus, a 4-stroke cycle engine only gets one power stroke per engine cycle.
Two stroke engines are a whole different ballgame as they get power out of each downward stroke of the pistons (i.e. two piston strokes per power cycle - two-stroke cycle engines):
- an upward stroke to compress the mixture and,
- a downward stroke to combust and burn it AND draw in a new mixture charge (sort of magic eh?) which provides torque to the crankshaft.
So a two cylinder 2-stroker like an RD400 or a Suzuki GT500 are 180 degree engines.
On triples, yup, you are correct, they don’t balance all that well unless you use a balancer shaft and sometimes even a torsional absorber to quell the lumpy torque pulses. Sometimes, re-arranging the crank throws (as in a cross-plane formation) can move the resonances to a different range where they aren’t as apparent.
Vee engines (V12s, V8s, V6s and V4s) have the additional complication that each bank of cylinders adds its effects to those of the other bank - and the magnitude and phasing of the effects depends on the angle between the banks of the vee. There are optimal angles for each engine configuration:
- vee-2 engines work best with a 180 deg. angle (like a BMW boxer engine);
- vee-4 and vee-8 engines work best with a 90 deg. bank angle;
- vee-6 and vee-12 engines work best with a 60 deg. bank angle.
Then of course, there are radial engines, rotary engines (NOT the same thing), Y-block engine’s (Napier Broad Arrow etc.) and H configurations like the Napier Sabre that powered the Hawker Typhoon and Tempest fighters in WW-II (these were among the first genuine 2000 HP airplane engines and they eventually got up to 3500 HP). The Sabre had two crankshafts geared together with each one being driven by two banks of 6 horizontally opposed banks of cylinders - for a total of 24 cylinders (with sleeve valves - no less). It was incredibly complex and it had a lot of theething problems at first, but once Napiers got it sorted out, the darned thing worked great!
The fact is that ALL piston engines have some measure of un-balanced forces or couples (not the same thing) but generally, the more cylinders you use, the less prevalent the out-of-balance effects.
What a sound though...
