Hurt Engine?

Lookfar

Lookfar

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Hello all. I'm pretty engine savvy, but looking for advice from the folks with years of Norton Twin experience. I had posted some time ago that I had now wanted to use my '72 750. (combat) as it "was intended" and "sporty", and as discussed I went with an alu 19" front rim, kept the 18" alu rear and Avon RR tires (90/90-19F 110/90-18R). Very Happy! Was finding myself turning in too soon on familiar roads. Only mods have been the Dunstall rearsets and the NH "M" bars as I prefer the position.
None of the above is important to my issue, just FYI from my previous posts. In 3 months and 1200 miles I have been really enjoying this bike in it's new roll. Dispite having to "tune around" the worn Amals she runs unbelievably smooth between 3.5K and 6K RPM with good power. (I'm keeping the 19T CS sprocket because of this).
Yesterdays oil change (every 1K+/-) revealed some "metalflake/sparkly" oil. As I was only riding this bike once or twice a year in the past I would not inspect it during it's yearly change.
Nothing magnetic, but plenty (to me) bronze/copper. I've sent for a Blackstone kit, ( I saved some). Oil has been Castrol GTX 20/50. I just changed it to RP HPS 20/50 ( a Jim Comstock recomended oil).
The dilemma: Continue to ride and check again, or tear into it?
The stats: It is a commando, 15K on the functioning ODO, I've had it for 15 years rarely ridden, rarely ridden by previous owner of many years. no previous history known to me.
Thanks
Bob
 
Lookfar said:
Hello all. I'm pretty engine savvy, but looking for advice from the folks with years of Norton Twin experience. I had posted some time ago that I had now wanted to use my '72 750. (combat) as it "was intended" and "sporty", and as discussed I went with an alu 19" front rim, kept the 18" alu rear and Avon RR tires (90/90-19F 110/90-18R). Very Happy! Was finding myself turning in too soon on familiar roads. Only mods have been the Dunstall rearsets and the NH "M" bars as I prefer the position.
None of the above is important to my issue, just FYI from my previous posts. In 3 months and 1200 miles I have been really enjoying this bike in it's new roll. Dispite having to "tune around" the worn Amals she runs unbelievably smooth between 3.5K and 6K RPM with good power. (I'm keeping the 19T CS sprocket because of this).
Yesterdays oil change (every 1K+/-) revealed some "metalflake/sparkly" oil. As I was only riding this bike once or twice a year in the past I would not inspect it during it's yearly change.
Nothing magnetic, but plenty (to me) bronze/copper. I've sent for a Blackstone kit, ( I saved some). Oil has been Castrol GTX 20/50. I just changed it to RP HPS 20/50 ( a Jim Comstock recomended oil).
The dilemma: Continue to ride and check again, or tear into it?
The stats: It is a commando, 15K on the functioning ODO, I've had it for 15 years rarely ridden, rarely ridden by previous owner of many years. no previous history known to me.
Thanks
Bob
Click to expand...
Stop.
You did right to oil test

concours

Thread 'Why we call it "inspection"...(2018)'

Why we call it "inspection"...(2018)
'74 Roadster, 43,000 miles (of which, the last 31,000 were well cared, not abused, and there is no reason to think the first 12,000 were different). No unusual noise whatsoever, and I listened.
Timing side main has failed.
  • Like

They never heal themselves
 
You really should take out the oil tank and clean it well and dry it well. Drain the base for a real long time. Squirt a real lot of oil into the top end and let it drain with the oil in the base. I don't know if you have an OEM oil filter in it, but you would see lots of metal in it if, you cut it open??? Cam bushings and thrust washers are brass and timing gear bushes. You need to get the sparkles out of the oil system.
 
Copper is the rod big end bearings wearing down usually. Bronze could definitely be the cage on the mains. If the mains went the grit they create probably would take the rod big end bearings with them eventually. I'm surprised that Norton engines don't start making a bunch of noise when that happens. Although it might be hard to tell given how much noise old British bikes make.

I've driven cars and motorcycles a long way with shot bearings. But only to get back home and tear down the engines. They get really loud and the engine gets shaky and unbalanced at certain revs before making it back to the garage. Never had it happen it with my Norton even though I've taken my Norton engine apart and the rod big end bearings were not looking too good. Never lost a main or a Norton engine yet. Probably just jinxed myself.

Take it apart. You might enjoy rebuilding it, if you never have.
 
Carl H said:
You really should take out the oil tank and clean it well and dry it well. Drain the base for a real long time. Squirt a real lot of oil into the top end and let it drain with the oil in the base. I don't know if you have an OEM oil filter in it, but you would see lots of metal in it if, you cut it open??? Cam bushings and thrust washers are brass and timing gear bushes. You need to get the sparkles out of the oil system.
Click to expand...
 
I had cleaned/ flushed the tank, and “flushed” the bottom end before refilling with the above. Was going to ride it for 100 to 500 miles and reinspect before I started to rethink. 44 years in Aviation so to me ANY metal in the oil is bad. Reached out to see if I’d get some of those “they all do that when pushed” responses!😀
 
Schwany said:
Copper is the rod big end bearings wearing down usually. Bronze could definitely be the cage on the mains. If the mains went the grit they create probably would take the rod big end bearings with them eventually. I'm surprised that Norton engines don't start making a bunch of noise when that happens. Although it might be hard to tell given how much noise old British bikes make.

I've driven cars and motorcycles a long way with shot bearings. But only to get back home and tear down the engines. They get really loud and the engine gets shaky and unbalanced at certain revs before making it back to the garage. Never had it happen it with my Norton even though I've taken my Norton engine apart and the rod big end bearings were not looking too good. Never lost a main or a Norton engine yet. Probably just jinxed myself.

Take it apart. You might enjoy rebuilding it, if you never have.
Click to expand...
I would think I would enjoy rebuilding it. Just unexpected and bad timing. I’ve got an R80st in a million pieces and a 900ss sp in the same condition. I got the Norton refreshed as it was a runner and I wanted to really ride it more seriously, including up to Quincy for the rally.
 
Lookfar said:
I would think I would enjoy rebuilding it. Just unexpected and bad timing. I’ve got an R80st in a million pieces and a 900ss sp in the same condition. I got the Norton refreshed as it was a runner and I wanted to really ride it more seriously, including up to Quincy for the rally.
Click to expand...
Sometimes, lady luck can be a cruel mistress 👊🏻👩🏻
 
Andover Norton sells a replacement crankcase sump plug that has a magnetic drain plug. It's a good way to keep an eye on magnetic particulate in your engine. I use it and I think a lot of people replace the original with it. A commando lifter/cam set up is metal on metal with no modern hydraulics or rollers in the valve train. It makes that lifter/cam interface a critical wear point. Your idea to use the Royal purple HPS 20-50 is a good idea. I use that same oil. (I'm not sure if there's a magnetic sump plug for the combat cases, maybe a combat owner will clear that up)

I had an intermittent growling sound at idle speed at the end of the last riding season. I figured it was one set of cam lobes growling so I pulled the engine apart and the 2 primary side followers were staring to pit very lightly. Everything else looked acceptable. I resurfaced all the followers and polished them, then reassembled everything over the winter. I also rebuilt the oil pump thinking that maybe low oil pressure contributed to the followers' wear.

I also decided to do a piston upgrade and barrel hone to the same size since the barrels measured under spec for the new pistons.

So, now I monitor the break in particles with the magnetic drain plug and I use a 150 micron filter in the funnel when I drain the oil to look for signs of metal particles. The growling sound is no longer there, so I believe that it was caused by the roughness of the cam followers. Only time will tell if the cam and newly surfaced followers destroy each other or decide to get along for a while...
 
Last edited:
The combat engine has many design flaws you can look up on this forum. All fixable. Mine had part of a piston ring stop the oil pump. Main bearing failure, Weak pistons, cam lockring failure, poorly located oil return in the case. If you want a reliable rider, take it apart.
 
Time for a thorough internal inspection. No use trying to "run" it clean.

You will thank yourself for doing the right thing, and I'm sure you'll address the low end performance of the carbs in one way or another.

Have fun, start a rebuild thread, and post lots of pix. This is not "Playboy" WE COME HERE FOR THE PICTURES! The interesting stories are welcomed, too...
 
Lookfar said:
Hello all. I'm pretty engine savvy, but looking for advice from the folks with years of Norton Twin experience. I had posted some time ago that I had now wanted to use my '72 750. (combat) as it "was intended" and "sporty", and as discussed I went with an alu 19" front rim, kept the 18" alu rear and Avon RR tires (90/90-19F 110/90-18R). Very Happy! Was finding myself turning in too soon on familiar roads. Only mods have been the Dunstall rearsets and the NH "M" bars as I prefer the position.
None of the above is important to my issue, just FYI from my previous posts. In 3 months and 1200 miles I have been really enjoying this bike in it's new roll. Dispite having to "tune around" the worn Amals she runs unbelievably smooth between 3.5K and 6K RPM with good power. (I'm keeping the 19T CS sprocket because of this).
Yesterdays oil change (every 1K+/-) revealed some "metalflake/sparkly" oil. As I was only riding this bike once or twice a year in the past I would not inspect it during it's yearly change.
Nothing magnetic, but plenty (to me) bronze/copper. I've sent for a Blackstone kit, ( I saved some). Oil has been Castrol GTX 20/50. I just changed it to RP HPS 20/50 ( a Jim Comstock recomended oil).
The dilemma: Continue to ride and check again, or tear into it?
The stats: It is a commando, 15K on the functioning ODO, I've had it for 15 years rarely ridden, rarely ridden by previous owner of many years. no previous history known to me.
Thanks
Bob
Click to expand...
Was the metal in the tank oil or sump oil?
Does the bike have an oil filter?
Was the metal sparkles or could you feel it?
 
I was talking to one of my friends at a race meeting . He had the timing chest open on a Triumph. The idler gear fell out onto the ground. He picked it up, and without cleaning it - put it back into the motor. I remember him telling me that whenever he has pulled a motor apart, there has always been metal collected in a corner in the bottom of it. And I think he might be right. I seem to remember cleaning bits of metal out of motors. Norton motors have chains inside them.
 
If it were me I'd be pulling the engine apart just to be sure ....

and given you want to eventually use the bike as intended - sporty - then I guess you'd be mad not to do so especially being a combat.

I'd say on the info provided - sparkly bronze / copper and so far the apparent lack of ferous debris you may have found any issue early, fingers crossed for zero ferous debris.
 
Bronze could be the camshaft thrust washer. 72's have the tab that is prone to breaking off. If the tab is broken the washer could spin and wear. Also, the tab could be floating around the oiling system.
 
htown16 said:
Bronze could be the camshaft thrust washer. 72's have the tab that is prone to breaking off. If the tab is broken the washer could spin and wear. Also, the tab could be floating around the oiling system.
Click to expand...
Yes , the bronze thrust washer locator tabs could have broken off , they were a bodge from the factory , using pliers to bend them over , so they would develop a crack , almost invisible until failure .
The only way to proceed is a teardown with careful inspections .
 

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