Compound fracture of the Crankcase.

I won't say g'day because it's not. After several extremelly hot days (38. 41. @ 42.9. deg. celsius,( 38 being about the ton), the temp has come back to a very respectable 29 deg. so I decide it 's perfect for a little ride.... Start the bike in the shed as usual, go and put helmet on...." Umm why did she stop, I've got the carbies pretty good at the moment", turn around to see...#**#!**#!!! OIL RUNNING DOWN THE FRONT OF THE CRANKCASE ONTO THE FLOOR. What the hell... Small split in the front of L/H case right behind the L/H engine plate. This engine has done about 300 miles on a new bottom end!. First I thought perhaps the Crank bolts had broken and the flywheel had moved out of alignment, I had seen this happen on a 500 CCM ( Clews Competition Machinery ) years ago but it hadn't hurt any thing as it too was only idling. However when I calmed down and decided that the sooner I get it apart the sooner I find out... Guess what... The Cam follower ( 'Tappet' in the Haynes manual ) has broken in half, the bottom piece has fallen behind the cam to the flywheel and tried to fit between the flywheel and the crankcase, well it didn't fit !. This is not heard of in these parts. Has any body had a similar problem and do I now replace the lot ?. It has marked the flywheel and the bottom of the sleeves, which in turn marked the very bottom of one piston skirt, ( standard bore in ex cond. and only needed rings when the bottom was done ), and has brocken a small piece out of the sleeve that holds the followers in place. Cam O.K. I think at this stage but not apart yet... To be cont...... Signed... Abrokenman. Do you follow er?. I going to have a drink.

Oh man, I have nothing constructive to say ,other than share some of your grief. Take some pictures for the forum.

I had a tappet come apart once on a short stroke 750 engine in an AHRMA race bike at Daytona, back in the '80s. It was an engine I had loaned to my racing partner to run in his F750 Commando. It trashed the cam, but the rest of the bottom end was still good, fortunately. That's the only tappet I had break in 20 years of racing them. I'd had all the tappets magnafluxed to check for cracks when I built the engine. It didn't break because of a fracture, but the stellite foot came off the body. We concluded that it wasn't brazed on properly. I've heard of it happening to others, but it's not a common failure.

Ken

Ugh, Trixie Combat lost a rod bolt at coasting 50 mph, rolled steel rod cap up like chewing gum to punch knuckle size fracture in case and a piece jammed cam lobe, which I assume is what caused lifter socket to crack 1/3 off, but rest of lifter appeared fine but for bottom scoring too. It took me a while to decide what went first that may apply to yours. Rod bolts were reused with new nuts from prior seizure d/t Aluminum gasket rubbing on slotted pistons [unknown to me], also going slow and easy so only damage then was parted piston and scored bore.
But apparently this caused a fatque crack that then expanded my oxidation/corrosion along the metal grains till 2/3 across it let go, just a matter of time not stress loads. Other bolt snapped next but its surface is bright new the other darkened. Maybe from prior seizure or over rev the lifter got a crack started so just a matter of time and temp cycles, rather than more tough beating.
I got another lifter set as did not trust the hidden damage.

I'm a hay seed now so used JBWeld to patch up Trixie's TS case and will see how it holds this spring. Patch is down low to rear so not an eye sore unless stooping to snoop. If you do weld, study up on how to beat distorted Al back to sealing fit. Likely your spot won't distort much as a weld near the seam.

I have seen the pad come loose from the bottom of the lifter a couple times. Always been on someone else's bike.
I saw a broken lifter body at Talladega racetrack one year. It had been lightened by elongating the holes in the sides obviously just a little too much. It had exited through the front of the case. Jim

I don't get the reasoning behind making a follower/lifter in 2 parts. Why not one piece construction? I've heard several stories of this failure, never had one myself.

Had it happen to me on my Mk3 Commando at the back end of last year, luckily the "shoe" from the tappet block fell harmlessly into the crankases and I got it out with a magnet. Spoke to Nick at Andover and he reckoned there was a dodgy batch kicking around a while ago, got myself a new set from them. Not that unusual, bad luck if it causes damage, the sudden extra 1/4" tappet clearance is the c l ue to stop the engine as soon as poss, the increase in noise is noticeable.
Funnily enough I'd just changed the oil and given the bike a service and was nipping to the shops on it when it happened, no racing or great rev's just ready to give up I guess.
Sorry to hear its caused a mess
Mde in two bits because the bottom pad is stellite, this is then brazed onto the body

Yes, I understand the pad is stellite, but why not just use a single piece construction of harder / hardened material?

grandpaul said:

Yes, I understand the pad is stellite, but why not just use a single piece construction of harder / hardened material?

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I've come across this several times in the days when the followers were sand-cast and the stellite pad was simply a flat semi-circle but not since the followers were changed to lost-wax cast with a spigotted pad.

I bought a Commando that had an extra stellite pad floating around in the bottom end (or caught up somewhere until I shook it loose). The PO had replaced the followers but not looked for the missing piece...

The errant pad had taken chunks out of everything - rods, pistons, barrels etc. but the crank was grindable and the cases just needed dressing to clean up the burrs inside.

Were the followers replaced on this engine or are they original issue ?

I make cam followers - its a single piece, milled from solid steel and gets case hardened and ground to size, and its lightweight! When I have finished the testing of these in my very radical 905 engine I can offer them if anybody is interested - they fit exactly the same as Norton followers - no mods needed.

comnoz said:

$$$$$$$$$$

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Too many "$"s...

I had a crankcase welded where it had cracked once by a welder who really knew his stuff.
Assuming you are going to get it welded, it's worth knowing that the guy I used, took the cases to a chroming plant he knew and it was left in their trichloroethylene de greasing bath for 2 weeks.
He said that many old cases are porous and when they've had oil sitting in them for 30 years, some of it gets soaked right in and when you heat it , the oil tries to expand and crack the case further.

If you do this, take the main bearings out first because they will rust in seconds when it comes out of the de-greasing bath.