Pistons firing in reverse?

[Gdubs]

Just pulled the head off my d902 to see why it was smoking so bad after rebuild. pistons are dirty, but functioning, head gasket wasn’t horrible

the main thing is, that everywhere I read, the firing order from fan to flywheel is 1-2-3, flywheel rotating counterclockwise

my pistons are firing 3-2-1 while hand cranking.

Anyone know how I managed to do this?

 

[eserv]

Just pulled the head off my d902 to see why it was smoking so bad after rebuild. pistons are dirty, but functioning, head gasket wasn’t horrible

the main thing is, that everywhere I read, the firing order from fan to flywheel is 1-2-3, flywheel rotating counterclockwise

my pistons are firing 3-2-1 while hand cranking.

Anyone know how I managed to do this?

No matter what you did you couldn't change the firing order! That is set by the grind of the camshaft. You could easily have installed the gears out of time though!

 

[Gdubs]

Right…it’d be impossible to change the crankshaft piston relationship

Would timing the gears wrong affect the firing order of the pistons though, or just the timing of the valves and fuel camshaft etc ?

 

[eserv]

Right…it’d be impossible to change the crankshaft piston relationship

Would timing the gears wrong affect the firing order of the pistons though, or just the timing of the valves and fuel camshaft etc ?

Are you turning the engine the right way? Counterclockwise from the flywheel end.

 

[Gdubs]

I believe so, looking at flywheel from back of machine it’s going counterclockwise
Trying to attach video but won’t attach

 

[eserv]

I believe so, looking at flywheel from back of machine it’s going counterclockwise
Trying to attach video but won’t attach

Just to be sure, The flywheel end is where the starter is!

 

[Gdubs]

Lol yes we’ve been staring at the video to make sure our eyes aren’t playing tricks on us
The flywheel is definitely moving counterclockwise (facing the flywheel)

 

[eserv]

Lol yes we’ve been staring at the video to make sure our eyes aren’t playing tricks on us
The flywheel is definitely moving counterclockwise (facing the flywheel)

Looking at a picture of a 902 crankshaft it appears to me that the piston order is 1-3-2 from the pulley end or 3-2-1 from the flywheel end. ( I don't have an actual crankshaft) If you start with 1 a top dead center 3 will be next then 2 then 1 again so if you put 3 at the top it is 2 next then 1

 

[Gdubs]

Yes that’s exactly how it’s firing

I’ll do more research on why it is different (possibly because it’s in a bobcat) but if not, would this be why the machine was smoking on startup and putting out a heavy plume of smoke while idling? There’s no changing it though, so I’m confused.

that being said, since I’ve been using the WSM to set the valves, and the WSM also says the firing order is 1-2-3, would the valves need to be re set accordingly?

 

[lynnmor]

that being said, since I’ve been using the WSM to set the valves, and the WSM also says the firing order is 1-2-3, would the valves need to be re set accordingly?

Turn the engine crankshaft till a valve completely opens, then turn the crankshaft one full turn, then set that valve. Repeat for each valve.

 

[GreensvilleJay]

wild guess....as engine's in a bobcat... they run it backwards' as the engine's in 'wrong way' with respect to a tractor that has a tranny and diff. I'm assuming bobcat is a hydraulic pump one(has to match pumps rotations...)

 

[Gdubs]

Yeah that all sounds logical
I used a kubota WSM and probably should’ve used the specific bobcat manual to rebuild the engine.

hetes the valve settings and I marked it with what I can only assume would be the proper order to set them now that I know they are firing reverse to what I was setting them to previously

 

[lugbolt]

Yes that’s exactly how it’s firing

I’ll do more research on why it is different (possibly because it’s in a bobcat) but if not, would this be why the machine was smoking on startup and putting out a heavy plume of smoke while idling? There’s no changing it though, so I’m confused.

that being said, since I’ve been using the WSM to set the valves, and the WSM also says the firing order is 1-2-3, would the valves need to be re set accordingly?

don't use the manuals recommendation to set the valve clearance. U can use it for the actual spec but not for the firing order. Do it with the eoic method. I've outlined this before so just search the site for it as I'm too lazy to type it all out. It's faster that way anyway.

 

[Gdubs]

Ok will do thanks

Now I’m thinking the fuel camshaft is timed to the main gear so that the injection pump sends fuel in the order of 1-2-3 (or maybe that’s not the case) So setting valves backwards may be futile ?

 

[Gdubs]

Not sure any of this matters at this point

took a close look at cylinder walls this morning and noticed two huge gouges in cylinder #1 wall

no clue how it could’ve happened.
pic attached

now I guess i pulling motor to have it machined (if possible)

 

[PoTreeBoy]

Disclaimer: I've never overhauled anything larger than a B&S, but I may have stayed in a HI Express.
1. Which direction does the starter spin the engine? If this is a reverse-rotation engine, it would have to have a different starter, camshaft, fuel cam, and (I'm thinking) oil pump.
2. Are you sure you're reading the firing order right? Remember, if #1 is on TDC power stroke, the next piston up (#3 presumably) will be on its exhaust stroke. Then #2 would come up on its power stroke. Like this:

0 deg 1 pow
120 3 exh
240 2 pow
360 1 exh
480 3 pow
600 2 exh
720 1 pow (same as 0)

If I'm stating the obvious, please ignore this and I'll just stand back and watch .

Edit: Ouch, sorry to see that.

 

[Gdubs]

As I crank it over by hand at the shop right now, your explanation makes perfect sense also, but I’m screwed anyway because of that #1 cylinder damage

 

[whitetiger]

took a close look at cylinder walls this morning and noticed two huge gouges in cylinder #1 wall

no clue how it could’ve happened

It looks to be from the wrist pin.

 

[Gdubs]

Yup I found the retainer clip in the oil pan

 

[GreensvilleJay]

could always have a sleeve installed....might be cheaper than another block ??