Some metal in the oil

concours · Apr 4, 2013

Matt Spencer said:
The Engines NOT supposed to be running , while You Tap that out . :wink:

Well, ANYONE could do it engine off, where's the challenge in that? 8)

Stillreel · Apr 4, 2013

I'd check your con rod bearings. It will get louder if they are starting to fail. Once their gone, time for a crankshaft re-grind. $$$

concours · Apr 4, 2013

Stillreel said:
I'd check your con rod bearings. It will get louder if they are starting to fail. Once their gone, time for a crankshaft re-grind. $$$

Good oil pressure, same as it's been for 5000 miles, continuous gauge readings. No bottom end noise, she sounds as it should. I effed up by not doing an oil sample last summer, I thought about it, decided to not go searching for trouble.

edgefinder · Apr 4, 2013

I'm still new to these Nortons so i've only seen the insides of my 750 I just opened up. I can tell you there is an enormous amount of folded over half ground off casting flash along seams to fall off in the oil. Reamer chips still packed in the bottoms of dowell pin and tapped holes. A lot of it was stained black like the one chip. I'd like to say don't worry about it if it runs good and no new sounds.

tyborg15 · Apr 5, 2013

Hello,

I see that the tap is marked 1 15/16ths. Is this the standard thread for the exhausts? and is it BSF, UNF or some other strange beastie? A local machine shop is closing and there are a number of large taps that I can get my hands on for scrap metal value. I thought it might be handy if I ever have need to clean the threads.

regards

Tyborg

kettle738 · Apr 6, 2013

That huge tap is quite something, really interesting to see; I hope never to need to do that job but I'd really like to know how you manage to get the tap dead square to the exhaust port....do you fix up a guide?

Trying to do that just by eye looks like a recipe for frustration and disappointment, (unless you have carefully honed skills) I'm hoping I might learn something here.

Mick.

concours · Apr 7, 2013

kettle738 said:
That huge tap is quite something, really interesting to see; I hope never to need to do that job but I'd really like to know how you manage to get the tap dead square to the exhaust port....do you fix up a guide?

Trying to do that just by eye looks like a recipe for frustration and disappointment, (unless you have carefully honed skills) I'm hoping I might learn something here.

Mick.

The tap was only to CHASE the threads that were disturbed during the welding process, NOT actually cutting NEW threads. That being said, it'd be real easy to start it wrong in aluminum. I used no fixture, just the eyeball, checked in two axi several times while starting slowly. Yes, I've been fixing stuff for a long time. (at least it FEELS like a long time, can't I retire already? :roll: )
As for learning something, you can read the whole story here, although some of what I did made the museum curators cringe/chuckle.
engineering-compromises-leading-exhaust-threads-stripped-t14363-30.html?hilit=exhaust

gtsun · Apr 8, 2013

I don't quite see the tap bits being those you found but stranger things have happened in Norton ville. Hope your not to stressed over it. I think I would just ride it and see. I did tear one 750 down due to my foolish youthful ignorance when I was a teenager & didn't know who to ask. Hope you get passed it so I can ride over and we can go have that Beer you mentioned... Good luck.

concours · Apr 8, 2013

I rode it for the first time (this season) yesterday, oil pressure is good, no knock. Will continue to monitor..

acotrel · Apr 9, 2013

have you looked inside the timing chest for the source of the metal ?- doubt it came from top end. If it is bearing metal you could have the big bang,but if it is stiil quiet, that is unlikely.

Bernhard · Apr 9, 2013

If you have run the tap and discovered the metal flakes afterwards then it is not impossible it came from there. Don’t ask me how I know.

Did you blow the port out of all the metal swarf afterwards :?:

concours · Apr 9, 2013

Bernhard said:
If you have run the tap and discovered the metal flakes afterwards then it is not impossible it came from there. Don’t ask me how I know.

Did you blow the port out of all the metal swarf afterwards :?:

Yes, (big ass)shop vac with a hose taped in as a crevice tool. Final with compressed air

Dances with Shrapnel · Apr 9, 2013

Bernhard said:
If you have run the tap and discovered the metal flakes afterwards then it is not impossible it came from there. Don’t ask me how I know.

Well I must ask. How do you know?

Some plausible routes for a metal chip in this instance would be through an open valve cover, open tach drive or open timing chest while generating chips but through the cylinder?

concours · Apr 9, 2013

tyborg15 said:
Hello,

I see that the tap is marked 1 15/16ths. Is this the standard thread for the exhausts? and is it BSF, UNF or some other strange beastie? A local machine shop is closing and there are a number of large taps that I can get my hands on for scrap metal value. I thought it might be handy if I ever have need to clean the threads.

regards

Tyborg

1-15/16-14, IIRC Published on Dyno Dave's website http://atlanticgreen.com/nhth.htm Thanks Dave!

concours · Apr 10, 2013

Stillreel said:
I'd check your con rod bearings. It will get louder if they are starting to fail. Once their gone, time for a crankshaft re-grind. $$$

Well, yes. The "check" I'm doing is the ongoing good oil pressure and lack of rapping noise from the lower end. I'll tear it down if need be, but I can't justify it on the small dots of aluminum.

Bernhard · Apr 13, 2013

Dances with Shrapnel said:
Bernhard said:

If you have run the tap and discovered the metal flakes afterwards then it is not impossible it came from there. Don’t ask me how I know.

Click to expand...

Well I must ask. How do you know?

Some plausible routes for a metal chip in this instance would be through an open valve cover, open tach drive or open timing chest while generating chips but through the cylinder?

Some years ago I took the short cut of cutting bigger valve pockets on the pistons, when i fitted a race cam to a jap 4. I used plasticine around the outside of the pistons to seal the bore to prevent any swarf entering into the engine.
When I had done I reassembled the head and run the engine. Then the oil warning light came on, I stopped the engine immediately and restarted it, run it again when the oil light repeated on again. I removed the sump and found that the gauge filter on the bottom completely covered in alloy swarf, which dropped down when engine was stopped?
A lesson on how not to take short cuts with your engine.

Dances with Shrapnel · Apr 13, 2013

Wow!

No chance the swarf did not somehow get into the motor through the open cam chain tunnel or pushrod tunnels. I am just struggling with seeing how relatively larger particles (swarf and chips and bits) can get past the rings.

Lessons learned indeed.

Bernhard · Apr 16, 2013

Dances with Shrapnel said:
Wow!

No chance the swarf did not somehow get into the motor through the open cam chain tunnel or pushrod tunnels. I am just struggling with seeing how relatively larger particles (swarf and chips and bits) can get past the rings.

Lessons learned indeed.

Cam chain tunnel was taped up, so I was and still am mystified how it happened.

concours · Apr 22, 2013

Borescope images of the piston crown

Dances with Shrapnel · Apr 22, 2013

Are those metal bits imbedded in the piston crown?

Some metal in the oil

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