Cracked drive side case

Bob Z. · Feb 1, 2020

This photo is from the ad for the 69 Roadster in the 'Seen on Craigslist' section.

What you you think caused this failure?

Dances with Shrapnel · Feb 1, 2020

Broken cam or collapsed cam follower fouling the cam.

kommando · Feb 1, 2020

Seller says

This is a 1969 Norton Commando 750 (Roadster). It has had a catastrophic failure in the bottom end of the motor - broken conrod that fractured the crankcases.

Fast Eddie · Feb 1, 2020

And the broken rod smacked into the cam, would me my guess.

Whatever the reason... it’s gonna be a mess in there !

rvich · Feb 1, 2020

A total mess. Hard to believe there will be any useful parts left!

concours · Feb 1, 2020

...and conrods break because the big end bearing fails.

Dances with Shrapnel · Feb 1, 2020

It'll polish out.

Fast Eddie · Feb 1, 2020

Thanks for that, I just spat beer all over my screen !

dynodave · Feb 1, 2020

Blow up buy an amature!
As they say been there-done that...
Upstate New York on Rt 12(Erwin Parkway) north of Boonville where the road goes into two lane. Yes just north of norton road....LOL
My (first bike ever) yellow 1970 roadster that I blew up in April 1971 at 105 indicated, coming down from 115 indicated, busted up the bottom of the barrels and and blew a big split in the front cases. WHAT A RIDE!!!!

Nothing usable except the head and crank. Took many months for Berliner and the factory to supply parts for the warranty rebuild.

I am currently building a copy of my 1st bike for nostalgic reasons. 70 yellow roadster pure stock...
Nov 1970 just a few months before blow up...

Fast Eddie · Feb 1, 2020

You gonna blow it up for nostalgic reasons too dd ?!

dynodave · Feb 1, 2020

Fast Eddie said:
You gonna blow it up for nostalgic reasons too dd ?!

Almost stock except for a 21t sprocket instead of 19t. AND it will have an oil pressure gauge this time to keep an eye on the small S/central oil tank situation.
It should not blow up this time. I know a lot more about NHT now...

ashman · Feb 1, 2020

Bob Z. said:
This photo is from the ad for the 69 Roadster in the 'Seen on Craigslist' section.

What you you think caused this failure?

Bit of JB weld will fix that up.

Matchless · Feb 2, 2020

Years ago I bought a 650 Norton twin with the same damage as that only worse. The front of the barrel had also cracked. When I removed the top end the DS rod had snapped. Amazingly the cam & crank were still perfectly useable.

Kvinnhering · Feb 2, 2020

concours said:
...and conrods break because the big end bearing fails.
View attachment 14201

I hope this didn’t happening in a Commando engine.
In my book, the carrillo rods is bulletproof in a Commando engine.

concours · Feb 2, 2020

Kvinnhering said:
I hope this didn’t happening in a Commando engine.
In my book, the carrillo rods is bulletproof in a Commando engine.

I don’t want to open a giant can of worms, but, when the bearing fails the rod (no matter who made it, from whatever material) is going next.(unless a savvy operator hears the rapping noise & shuts down)
The whole “super strong, lightweight rod” is only a benefit if higher RPM use is planned. It provides no benefit when the bearing fails.
That piston/rod pictured is from a Mitsubishi car engine.

Time Warp · Feb 2, 2020

It probably doesn’t matter to much if the shell is getting a consistent oil supply.

Cracked drive side case

Bob Z.

Dances with Shrapnel

kommando

Fast Eddie

rvich

concours

Dances with Shrapnel

Fast Eddie

dynodave

Fast Eddie

dynodave

ashman

Matchless

Kvinnhering

concours

Time Warp

.......back to the 70's.

Similar threads