Slappy M944

[koko64]

Yeah it had the old shiny studs, I dont know how they didnt snap. You"re right about them being brittle as I've wrecked cobalt drill bits and Easiouts removing a broken one that was snapped off flush to the crankcase. Bloody hard material.
The bike is from interstate and the bike and its issues migrated down here. No sign of the piston hitting the head and it wouldnt surprise me if the barrels were bored to 94mm sans pistons. From the owners old dyno reciepts the pistons have done at least half the bikes 90000 miles.

Pistons are 93.4mm at/above the rings and varies down the skirts. The bores are 94 just below the spigot line and different values at the base. I can nearly wedge a 0.5mm feeler gauge. Im getting severe rocking of the piston in all directions when in the bore. Everything appear out of round.
Regarding riding hard in a hot climate,  sticking with the stock bore size with hi comps is a good idea with these 900 motors.

[ducpainter]

Did you get the flywheel off yet?

[koko64]

I was working on another M900. I'll have another shot tomorrow.

I dont think the cylinders or rear head are useable except for spares like tensioner bearings, cams, valves, rockers and the like. A full rebuild with new barrels and pistons and another used rear head would be needed. You wouldnt want to pay someone to do it. Maybe re coated cylinders at 944 but I reckon they are out of round due to a loose platform and thermal issues.
A spare parts donk I reckon.

[ducpainter]

I'm just curious about where the fur came from.

[clubhousemotorsports]

Just get the already bored cylinders re-plated, they will likely be fine with a re-plate hone job. With the mileage you gave it is not bad life out of the set so picking up some 900 high comps or a set of st2 pistons for a nice low comp 944 motor would be worth doing for the cost of a re-plate job.

What was wrong with the rear head again? I would bet it is all easily fixed and worth doing so, I have not seen anything yet that is a problem a good freshening would not solve.

[koko64]

Did some research.
The rear head is too soft according to a tech who tested it (nice Wurth tool). He did the repair on the head some time ago once it came down here. It has been re-machined and lapped into the barrels and still warped later, the gas trail blowing out the rear o-ring. The bad studs contributing to the state of the heads according to this guy. He builds performance motors. "Chalky alloy" was the term.

That's good news about the barrels, not sure I would like to go more than stock bore hi comp on my own bikes though with our hot summers. The extra meat is good. I guess some JE944 pistons and recoated cylinders honed to match are a possibility?

That motor will need a full rebuild. Hope the material is only bearing and not crank fur.

[Speeddog]

Looks like main bearing fur to me.

Big end bearing fur is like so:



And it looks like panning for gold, but nobody's happy when they see it:

[pepeducat]

😐

Outch

[Monsterlover]

I can't add anything other than

This thread is gruesome.

I took a motor apart today and mine really didn't look like this at all and I'm very happy about that

[koko64]

Thanks for everyones comments and assistance.
The motor will be used for spares or rebuilt later.
Cheers.

[clubhousemotorsports]

This thread is gruesome.

Meh................  it looks like that most times Ducpainter drops something off.

[ducpainter]

Meh................  it looks like that most times Ducpainter drops something off.

He fails to mention he was the last one to work on it.

[Monsterlover]

Gotta pay to play, my friends.

Ask me about how to get a piston in your air box

[koko64]

Gotta pay to play, my friends.

Ask me about how to get a piston in your air box