Oil Pump Discovery

CanukNortonNut · Jan 25, 2014

Interesting find. :shock: While I was refurbishing my oil pump on my 74 850 engine I removed the four bolts to disassemble of the plates. I discovered when this pump was opened, that the idler dowel pin was missing. Very Curious. :? It’s a good job I checked but I am baffled why it is not there. Previous fingers were in there as this bike I purchased a number of years ago.
CNN

comnoz · Jan 25, 2014

Had it actually been run that way? Jim

CanukNortonNut · Jan 25, 2014

comnoz said:
Had it actually been run that way? Jim

Jim
Yes. I ran this 74 engine for two years. About 3000 miles before I switched it out with a 73 engine that I had available. There were too many oil leaks on the 74 engine with two broken barrel fins and I wasn't too happy how it was pulling after 4 grand and above. The two broken fins were the tell tail evidence that there was a PO "real winner" trying to fix this old girl. I was suspecting a bad cam but when I looked at the cam if was fine. It also wet sumped badly. I guess the gears just ran by being encapsulated. I didn’t have an oil gauge so I can’t tell you what the pressure would be at the top of the head.
CNN

Hobot · Jan 25, 2014

Hehe shaking head at what others finding can tell us that matters. Will be very educational once parts examined to see what was getting starved the most, if they even do. My quess is lack of oil to head made cam lobes get worn down to stifle breathing. Still reviewing all the posts on oil quages reveals by the time they noticed, the engine was telling them its was too late any way, even if not siezed or blown up. If not much wear found then very encouraging on oil pump conditions to worry about.

texasSlick · Jan 26, 2014

Was there any evidence of the gear spinning on the shaft? That is shaft gouges , shine, rings, etc. Perhaps it was a tight fit and no undue wear occurred on the engine.

concours · Jan 26, 2014

Pics please...

CanukNortonNut · Jan 26, 2014

Its been a while since I used photobucket but I will give it a go.

Getting stuff test fitted before it all goes together.

Well would you look at that.
CNN

CanukNortonNut · Jan 26, 2014

texasSlick said:
Was there any evidence of the gear spinning on the shaft? That is shaft gouges , shine, rings, etc. Perhaps it was a tight fit and no undue wear occurred on the engine.

No tex
The gear I.D. looks fine. No indication of galling and they measure 0.376" ID
It amazes me that the pump actually had any pressure.
The strip down of the engine had very little wear on the throws of the crank. During the rebuild process I had an engine machine shop just polish the journals. Piston cylinder wear was less than 0.002” so I just had it re honed and I will just use new rings. So no re-bore. Again like I said earlier the cam looks good as well as the tappets so Oils was getting to the whirlie bits. I recall that I used Kendal straight weight 50 for oil before tearing the engine down. Maybe that was enough to get the oil to the top of the head enough to lubricate the rockers.
CNN

Hobot · Jan 26, 2014

Very extra good lack of wear findings so kind of puts a real evidence damper on the need to increase oil pump flow and the wisdom of Norton to remove oil guage option after a season or so of freaked out customers.

slimslowslider · Jan 27, 2014

Found this patent sketch, Schmitter gear pump with shaftless idler

CanukNortonNut · Jan 27, 2014

Would the diameter of the idler shaft be the same as the driven?
If someone has a oil pump open and a vernier or micrometer could you give me the idler shaft Diameter. I tried to use a .375” steel dowel pin and I find that it is too tight.
Thanks in advance.
CNN

slimslowslider · Jan 28, 2014

I just measured 0.374", 9.5 mm, with a vernier.

comnoz · Jan 28, 2014

About .0005 clearance is right.
Use a hardened shaft. Like an old valve stem or harden some O1.
If you use a shaft that is soft like the gear it will gall. Or use an al/bronze shaft. Jim

CanukNortonNut · Jan 28, 2014

Thanks Slim and Jim.
I was thinking Ampco18 albronze would work. I can spin that down on a lathe.
Cheers,
Thomas
CNN

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