Sohc or ohc ?
 

Hello hubbers,
On a single cylinder motorbike engine is ohc and sohc actualy the same?
Ifnot what is the difference for a single cylinder engine.

There is a lot of info on this on car engines with more than one cylinder.

Thanks for your help!

An ohc (overhead cam) engine could be either sohc (single ohc) or double ohc. There are a few oddball tohc (triple ohc) bike engines but to the best of my knowledge none of them are singles.

thanks for your answer,
So if the single cylinder isnt a Dohc,it is a Sohc with is the same as a Ohc (on a single cylinder)if i understand it correctly.

To call a single cylinder engine ohc it must have either one or two cams located above the valves. There are alternative possible locations for the cams - either in the crankcase or in a few cases halfway between the crankcase and the head.

Usually if you read that an engine is OHC it means single cam. The marketing people don't miss a trick and if it's got twin cams they'll let you know - it'll be stickered as DOHC or Twin Cam.

totaly clear now!!
many thanks for explaining it :thumbup1:


I asked this question because there are a few single cylinder engines of honda saying "ohc"
while other brand with a also single cylinder engenines marked there as "sohc".



Saludos and thanks BofB!

So if the engine is laid down a la Moto Guzzi or Ducati single would it then be a SAOTHC (Single ahead of the head cam)? ;-)


Andy

Anaconda-

It looks like this has been clarified for you, but just to be sure I'll offer this:

The word "single" with regard to cylinder count and single (sohc) and camshafts are actually unrelated. I'm not sure but this may have something to do with your initial question.

All four stroke cycle engines have at least one camshaft somewhere (forget sleeve valve engines for this discussion). It may be in the block where it can operate valves that are also in the block (a.k.a. side valve or flathead) or if the valves are in the head, pushrods and rocker arms would be required to actuate the valves. When the cam is in the block in virtually all cases only one cam is needed even with a Vee type engine. Yes there are exceptions but they are unrelated to valve control.

The only other location for a cam is in the head, as in SOHC and DOHC. The single and double having to do only with the number of camshafts, not the cylinder count. So everything from a single cylinder to a v-12 can be of a SOHC design or a DOHC. The reason cams were moved to the cylnder heads is for more accurate valve control. So any engine regardless of the number of cylinders can benefit from an overhead camshaft design. Some of the considerations in the choice of a single overhead cam and a double overhead cam are cost, and mechanical complexity. Two cams cost more, but the valve actuation can be simpler. A SOHC design will usually require rocker arms for at least half of the valves. With the classic DOHC design the cam lobes act directly (through the shim bucket) on the valves, no rocker arm required.

Interestingly, going back to the flathead (valve in block) engines, they enjoy valve control that is every bit as accurate (maybe even a little more so since they can dispense with a cam chain) as an overhead cam engine since they also can act directly on the valve.