150 miles on a new motor and this

Pete Komarek · Nov 20, 2019

I've had multiple problems with rebuilding my MKIII. New Emgo .020 pistons, new valves, guides, springs, E-ignition,coils, blah blah. The bike would miss under acceleration and kept getting worse. Pulled the plugs and one was very oil fouled. Pulled it apart and this is what I found.

Left side has a scored cylinder, right side is good but burning oil. Did a leakdown on both cylinders, both are leaking out the exhaust valves. maybe 150 miles and I'm prety tired of this crap. Brought the head to the machine shop that did the work. they will disassemble and call me. this is a performance shop that has worked on Nortons and Triumphs and is well regarded.

baz · Nov 20, 2019

Christ is that the circlip hanging out in pic 1 ??

Pete Komarek · Nov 20, 2019

Yup! Gut wrencher there. Actually the circlip is in pieces. I have to fish around in the bottom end with a magnet. Got 1/2 out so far

baz · Nov 20, 2019

There was a thread on here recently about wire circlips
I'd search it out and have a read of it
Hope your damage isn't too bad I feel your pain

Ron L · Nov 20, 2019

Pete Komarek said:
Yup! Gut wrencher there. Actually the circlip is in pieces. I have to fish around in the bottom end with a magnet. Got 1/2 out so far

Don't bother. It needs a complete teardown, inspection, and cleaning to make certain you don't have more pieces in the oil galleys or rod bearings or crankshaft.

MichaelB · Nov 20, 2019

That is just ugly.
Were the supplied Emgo rings and circlips used?

https://www.accessnorton.com/NortonCommando/piston-circlips-again.29003/

APRRSV · Nov 20, 2019

Pete Komarek said:
I've had multiple problems with rebuilding my MKIII. New Emgo .020 pistons, new valves, guides, springs, E-ignition,coils, blah blah. The bike would miss under acceleration and kept getting worse. Pulled the plugs and one was very oil fouled. Pulled it apart and this is what I found.

Left side has a scored cylinder, right side is good but burning oil. Did a leakdown on both cylinders, both are leaking out the exhaust valves. maybe 150 miles and I'm prety tired of this crap. Brought the head to the machine shop that did the work. they will disassemble and call me. this is a performance shop that has worked on Nortons and Triumphs and is well regarded.

APRRSV · Nov 20, 2019

Did the performance shop do the piston install?

jbruney · Nov 20, 2019

Those pics just put me off my supper.... A sad tiding. I hope the damage doesn't get too extensive.

Richard Tool · Nov 20, 2019

Bad luck - you obviously have the barrels off so you have come this far . Forget the magnet bit - tear the whole thing down

MexicoMike · Nov 20, 2019

Looks like faulty installation of the circlip. I realize that there has been some concerns re certain types of circlips but to have ANY type of circlip fail on an essentially stock motor that has a properly operating oiling system seems very unlikely to me.

ashman · Nov 20, 2019

Even professional engine builders have bad days, a friend of mine saved up and brought his first new bike a $30k Harley rode it 15 miles and it blew up, someone who put the pistons in forgot one circlip, they wanted to rebuild his motor but he demanded a complete new bike, it took him weeks before they caved into his demand.
Not looking good on such short miles and hope people admit to their mistakes and yes I would completely pull it down, best to be safe than sorry later.

Ashley

comnoz · Nov 20, 2019

If the junk black circlips that come with the Emgo/JCC pistons were used, this is the result I would expect.

The pistons are fine -the circlips are not usable.

elefantrider · Nov 20, 2019

Could be poorly installed oil rings (rt) and circlip (left side). Need bigger and better photos.

o0norton0o · Nov 20, 2019

Circlip failure, just look at the gauling on the piston at the edge of the wrist pin opening. The dislodged circlip was moving up and down with the piston hammering at the edge of the piston until it disintergrated.

When I had a circlip pop out at 65 mph on my bike some years ago, the bike made a huge "POP" sound and a puff of blue/white smoke went out the tail pipe on that cylinder's side. I pulled the clutch immediately, shut the bike off and coasted to a stop on the side of the road. I called my friend to pick up my van and pick me up within a few hours..

Not much to say, except that I don't hear of circlips popping out on other makes of bikes, so there must be something about guys that work on nortons that make them improperly seat their piston's circlips....

.

comnoz · Nov 20, 2019

It's more just the fact that due to the long stroke and rpm potential of a Norton the piston speed is in the stratosphere. This means only the best circlips are suitable in a Norton.

IE, piston speed in an F1 engine reaches ~21 MPS.

A Norton hits 21 mps at 7050 rpm.

gortnipper · Nov 20, 2019

Damn. Closest I'll ever get to F1 type performance. LOL

jbruney · Nov 20, 2019

Regardless of who, what, when, where I feel really bad for Pete on this... A most horrifying disappointment to have to suffer.

comnoz · Nov 20, 2019

jbruney said:
Regardless of who, what, when, where I feel really bad for Pete on this... A most horrifying disappointment to have to suffer.

I would have to agree.
I hope whoever did the work or supplied the parts will stand behind it.

acotrel · Nov 20, 2019

There is probably not much side loading of the circlips unless the bores of the little end and big end are not parallel. I once bought a set of barrels off a 650 Triumph which had two deep grooves in one side of one bore. If you use the flat circlips, you might get a heat treatment problem. The wire ones are usually OK - not so many changes in dimension. But I've never had a circlip fail in service.

150 miles on a new motor and this

"Sons of Arthritus"