Hitchcocks Forum

Hello again,
Just a quick post to check that I have inserted my new piston head correctly.

Looking at the engine from the timing side. (So front wheel to my right) When running, the crank shaft rotates in a clockwise direction.

Therefore, was I correct to assume the piston thrust face is toward the inlet side of barrel? Opposite to rotation.

It's not too late to rotate piston head if need be

Best regards.

That is correct, however pistons are usually marked with an arrow pointing to front of engine, but if not the valve cutaways are usually different sizes, exhaust smaller and going to front.

Yes, my piston does have an arrow, but no recesses for valves, I assumed the arrow pointed toward the major thrust face. In this instance the piston skirt is larger on the arrow side, so I'm assuming this is thrust side. The arrow points towards the inlet side, not front of engine ?

As I said, the arrow usually points to front of engine. I have never seen a reference to thrust faces as a way of fitting a piston. You don't say what bike it is, or year. Is it a 2 or 4 stroke, seeing as there are no valve cuttaways? If the crank turns clockwise looking at timing side, ie right side of bike, then as you say, the thrust face of piston is on inlet side, assuming the inlet side is at the back of engine.

Sorry, Royal Enfield 2011 Bullet classic EFI C5 4 Stroke. I am fitting a Wossner piston to a big bore Barrel 535 cc.

I have just realised the Piston has an offset wrist pin (Gudgeon pin) So offset toward thrust side as stated on Wossner web site.

All becomes clear