Yanmar YM 2000 Piston & Rods

Gary C. · Nov 24, 2011

Hello,I have been reading here for a couple years & have learned alot. I just bought a YM 2000 with engine problems that the owner already had apart. My question is which way the rods are suppose to go back on the crank ? He does not remember how they were removed & didn't mark them.There are numbers on one side of the rods & one side of the bearing caps. I have a shop manual ordered but it won't be here for a while. Thanks !

winston1 · Nov 24, 2011

Can't guarantee about the ym2000 but the manual for a ym220/226 states the identification on the rod is to face toward the flywheel. That is the closest us version to my ym2002.

Car Doc · Nov 25, 2011

There will be an id mark on the rod but for further proof I would look at the pistons as long as they are still on the rods and that will tell you for sure.

The shape of the valve indents and injector spray residue on the piston top is where you look for clues plus there will be a front mark on the pistons also.

fyi If you cant 100% positive match a cap to a rod take it to a machine shop and have them match them up or you will ruin a lot of parts.

Gary C. · Nov 25, 2011

The rods & caps do have numbers on them so I can match them up. I don't see anything on the pistons . They are flat top, no arrows or anything & still on the rods.I have a couple pictures. Maybe . Thanks for the help.

Car Doc · Nov 25, 2011

Glad the rods are matched up! :thumbsup: So he had the pistons all cleaned up and no carbon on them is what I gather?

There is usually either just writing on one side or a dot or a boss or an arrow cast in somewhere on all the engines I worked on subtle but its there somewhere. edit: It can even be under the top looking at the piston from underneath and if not it may be unidirectional which I have never seen but my education is automotive based...

Some times there will be an oil hole in the side of the rod at the cap area that is there to either oil the piston pin and/or the cam lifter lobes so that can be a clue using pure logic in the absence of a manual. hth

Gary C. · Nov 25, 2011

Thanks Car Doc,I checked the pistons again & don't see anything at all on top.Maybe the new ones will be marked.I think a bad head gasket started all his problems. I see a newer water pump & radiator on it. My local machine shop reworked the head with new valves & everything. Looks like new! Thank you also Winston, I am going to go with what you said when I install the rods .