(http://i1024.photobucket.com/albums/y304/tonykokonis/1024x768_bestfit%203_zpsdtfphonw.jpg)
An M944 came in with bad piston slap and a warped rear head which blew oil out towards the rear exhaust from the gas trail taking out the oil return O-ring. The sump plug is shown. I am about to tear into it and suspect the piston skirts have finally slapped through the Nikasil linings. The piston slap was louder than the clutch.
The rebore may have been mismatched to the hi comp 944 pistons although after 90,000 miles that's an unfair charge. The stock pinging ignition and warped oem engine studs (circa '94) are probably the culprits. [bang] It's amazing the studs didn't snap. The whole top end motor stability was compromised.
I'd be surprised if you didn't find the L/H main bearing has failed and the 'slap' is the piston hitting the head.
AMHIK. ;)
Thanks DP. So main bearing causing major piston rocking? There was certainly a clear slap rather than a knock to the motor. Should see inside soon. Interested in opinions as to the material.
(http://i1024.photobucket.com/albums/y304/tonykokonis/20160713_173508_zps1rborhkl.jpg)
An engine swap fixed things. New hotness, old busted in the background.
Will a magnet grab Nikasil?
Thanks. Shows how much I know about metallurgy. ;)
I'll post more pics once I open her up.
You'd be surprised how much all those fins will change the noise.
Pull the left cover first.
I'll open her up tomorrow.
Cheers.
The little ends have been pounded by long term pinging (stock ignition on 944 hi comp) and the wrist pins and pistons were rocking laterally in the bore nearly 5mm! The piston skirts were slapping the sides of each bore as evidenced by the scuff marks. How a piston didn't hole is amazing because they got hammered.
That material is still coming from somewhere, so I'll have the flywheel, etc off this arvo and see what's up. We'll see how the mains and big end fared.
Not fitting hi tensile studs allowed the engine platform to be insecure and this has warped the rear cylinder head. The oil return O-ring was damaged by a stray gas trail and oil was pissing out. The head material may be too soft now to be bothered re-machining and lapping it. A hardness test will confirm.
Sounds like it's comprehensively rooted. :-\
Yep. A major overhaul.
Further examination has revealed massive piston to bore clearance, both laterally and fore and aft. It exaggerated the wrist pin play. A mate said he has seen some bad overbore jobs locally and the pistons don't look as bad as the piston to bore clearance should suggest. Considering the mistakes made when this 944 was put together I'm starting to think the job was borne bad.
Oh well it's a spares motor now.
I haven't got the flywheel nut off yet. My rattle gun's rattled.
(http://i1024.photobucket.com/albums/y304/tonykokonis/20160914_190725_zpsb60v50ia.jpg)
(http://i1024.photobucket.com/albums/y304/tonykokonis/20160914_190755_zpsq6r83zde.jpg)
Is that a Pistal?
No that may be a Bucci or Gia.ca.moto. they have not been used for quite some time. what was the piston to wall? Any idea of the mileage on the pistons? to do a 944 kit they had to have the cylinder bored and plated but there were "kits sold" IIRC. One would hope it was made to fit at assembly but some drop in pistons are sold on the small side because the piston maker has no idea if the bike has an "A,B or C" spec cylinder.
The metal on the plug is from a bearing failure or the starter clutch probably. If you were hearing "piston slap" on a oil jacketed motor it must have been very loose or Nate is right and it is a main bearing allowing the piston to touch the head. Any shiny spots on the tops of the pistons where the carbon has been knocked off? It is NOT uncommon for big bores to warp the head between the rear studs due to the smaller sealing surface and higher temps/pressures.
The old studs were not weak as much as Brittle, this is the chrome studs only. It is actually lucky that they were still okay after the heads were off for the 944 kit, are you sure they are OEM?
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.
Did you get the flywheel off yet?
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.
I'm just curious about where the fur came from.
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.
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.
Looks like main bearing fur to me.
Big end bearing fur is like so:
(https://c6.staticflickr.com/9/8198/8170858973_293322ff72_c.jpg) (https://flic.kr/p/ds2MGR)
And it looks like panning for gold, but nobody's happy when they see it:
(https://c4.staticflickr.com/9/8126/8658488067_710623dd10_c.jpg) (https://flic.kr/p/ec81R2)
ðŸ˜
Outch
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 ;)
Thanks for everyones comments and assistance.
The motor will be used for spares or rebuilt later.
Cheers.
QuoteThis thread is gruesome.
Meh................ it looks like that most times Ducpainter drops something off. [evil]
Quote from: clubhousemotorsports on September 19, 2016, 08:01:50 AM
Meh................ it looks like that most times Ducpainter drops something off. [evil]
He fails to mention he was the last one to work on it. :-*
[laugh]
Gotta pay to play, my friends.
Ask me about how to get a piston in your air box ;D
Quote from: Monsterlover on September 19, 2016, 04:51:12 PM
[laugh]
Gotta pay to play, my friends.
Ask me about how to get a piston in your air box ;D
[laugh] [bang] [laugh]