Discussion in 'Norton Commando Motorcycles (Classic)' started by Schilling, Nov 22, 2018.
Sorry,,,I neglected to add any description to the photos, the images are the two magnetic plugs,,,one the engine oil drain plug the other the plug in the sump drain plug. the solid bit sticking up from one of the plugs was then set next to the penny for size comparison. this engine is from a 1973 850 with 12,500 miles on it. I've owned for a year. Ive put about 2,000 miles on it. it had pretty extensive engine work done to it in 2007 and 2008 at about 10,500 miles. I changed the engine oil right after buying it and again about 1,000 miles ago,,,there were virtually no metal bits attached to either plug when the oil was last changed. the last ride on the bike was about 30 days ago and it started to, what i felt, was misfiring,,,,so i rode the 4 blocks home. thought at the time it was a tank of bad gas,,, checking the plugs then i found them to be pretty black and a bit sooty. I also noticed an oil tank leak (unrelated to what i see on the oil drain plugs now). I removed the oil tank, sent it to CNW for upgrade/repair and will be getting it back next week,,,,,so,,,I thought it prudent to drain the remaining engine oil via the two drain plugs in anticipation of the new oil tank and this is what I found... thoughts?
The chunk next to the penny ...... is it magnetic? It looks like copper in the pic.
First step: a compression test.
Yes, the bit next to the penny is magnetic; it was attached to the rest of the particles on the drain plug to the right in the image but I separated it to take a size comparison photo. could be a section of a piston ring?? there are many tiny bits of copper/bronze (not sure which metal for sure) that show up on the blue paper rag in the photo, these non-magnetic bits had settled at the bottom of each drain plug ("bottom" meaning where the threaded portion meets the head)
I first thought it to be a piece of a ring, but the color contradicted that. Being magnetic, it is likely piece of a ring.
Have you been running hot, or idling long on a very hot day prior to the symptoms you described as misfiring occurred?
I am thinking seized piston, the brass or bronze stuff you see being the expander ring.
A compression check should be definitive.
Update: just read Deets55 post which came in while I was writing this .... I think he has nailed it as a piece of circlip.
The rest of the magnetic debris might be the result of the gudgeon (wrist) pin gouging the cylinder wall.
Sorry .... don't shoot the messengers. Keep us posted.
could be,,,i'm going to try to trace the bit and extend the curve to full circle to find the diameter, thank you for your response
Thank you Slick for your response, very little of my riding was/is done hot, no excessive idling either, generally first or second kicks to start, put on my jacket and head gear, and off I go. I'll work on getting the compression test done this weekend, thanks again for your input/insight
O.K. No over heating means rule out piston seizure.
Circlip coming out of groove can happen anytime.
A bore scope can determine if there is a groove at the 3 or 9 o'clock position in the bore. I would do the compression test .... if poor, pull the head.
I have to say if I saw that lot I would strip the motor straight away
Yeah, circlip seems most likely I’d have thought.
Whilst that’s bad news cos it means a top end rebuild... IF you’re lucky and IF you caught it in time, you may get away with the bottom end being OK.
Fingers crossed for you.
It looks like a fragment of a square section circlip. Too tight a radius for a piston ring, lack of sharp edges and it looks like a die cut piece. See other threads here about proper installation of these types of circlips. It probably wallowed out the pistons enough to pass the circlip fragment to the crankcase. Well that is my theory.
i think the radius is to big for a circlip.
tomorrow (Friday) I'll do a boroscope check as well as a compression test. the diameter of the solid bit turns out to be very close to the same as the penny,,,right about .7 of an inch. thanks again to all that have given input and responses, much appreciated !
thank you Sir
I'm guessing at least part of the motor will be getting refreshed, could be worse,,,it could have happened much farther away from home,,,and where I live cell phone reception is spotty at best,,,so I was able to get it back here pretty much straight away
Thank you, messengers don't get shot by me. I would rather hear as much info/input as possible instead of the other way around,
Crank bearing shoulder
the thickness of the solid bit is (right about) .034",,,the thickness of the edge of the penny is right about .059
the coloring of the solid bit in the picture makes it look more copper colored than it really is,,,it's really just a gray magnetic piece of metal
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