Oil Leak

Marcb · Mar 19, 2021

I just finished up sprucing up a mint 1970 750 Commando and was going to take it out for a thrust run when I noticed a slight oil leak. About 1 drip every 5 seconds. Warmed it up and oil started dripping more. Leak is between the head and cylinders. After running it some more the leak got really bad. Now it is leaking from the rear now also. (Both leaks near the push rods). My question is should I re-torque the head bolts or just tear it down and put a new head gasket in. Motor has 150k miles on it and has never been touched except for normal maintenance.
Thanks
Marc

MexicoMike · Mar 19, 2021

Well...it wouldn't hurt to re-torque the bolts and see what happens. But frankly, I have never seen re-torqueing actually stop a head gasket leak on any vehicle in my entire life of doing engine work on everything from motorcycles, to cars, to John Deere combines, to marine diesels to...you get the idea. .

Torontonian · Mar 19, 2021

MexicoMike said:
Well...it wouldn't hurt to re-torque the bolts and see what happens. But frankly, I have never seen re-torqueing actually stop a head gasket leak on any vehicle in my entire life of doing engine work on everything from motorcycles, to cars, to John Deere combines, to marine diesels to...you get the idea. .

I thought the same way until I tightened up the rocker feed banjo bolts and all was solved.

Marcb · Mar 19, 2021

I agree with you, but since I have to tear it down anyway I think I will put a new head gasket in. I'm from the old school that you put new head bolts in too. Do you agree?

robs ss · Mar 19, 2021

Marcb said:
I agree with you, but since I have to tear it down anyway I think I will put a new head gasket in. I'm from the old school that you put new head bolts in too. Do you agree?

Personally I wouldn't.
Commando head bolts aren't taken up to proof stress so are good for re-use as long as they're in good condition.
I do agree though in replacing the 3/8" bolts at positions 1, 3, 4, 5 & 6 (see pic below - they're the ones either side of the spark plugs plus the one between the pushrods) with ones that have been waisted to 5/16". the rest are already 5/16" and/or clamp iron not aluminium. I believe in the theory that it makes them that bit more springy so they don't deform and creep the head itself. Could be why yours is leaking? cNw sells them (https://coloradonortonworks.net/cnw-head-mounting-kit.html) which are very good but you could get you own turned down. Just remember that if you have yours machined then have them also polished to remove machining marks (stress raisers).
Cheers

baz · Mar 20, 2021

That's a lot of oil
Are you sure it's not the head rocker oil feed leaking somewhere?

Nortoniggy · Mar 20, 2021

I'd be stunned if it's never been apart in 150k miles. Have you owned it from new?

Marcb · Mar 20, 2021

Nortoniggy said:
I'd be stunned if it's never been apart in 150k miles. Have you owned it from new?

I'm the 3rd owner. Bike has 450,000 miles on it. Previous owners took good care of it. It looks brand new.

Marcb · Mar 20, 2021

baz said:
That's a lot of oil
Are you sure it's not the head rocker oil feed leaking somewhere?

That's the first thing I checked.

Deckard · Mar 20, 2021

Looks like my garage. Jeep Cherokee, stash of toilet paper.

MexicoMike · Mar 20, 2021

Torontonian said:
I thought the same way until I tightened up the rocker feed banjo bolts and all was solved.

I should have clarified... I was referring to head gaskets, not various other fittings. I agree that just about any leaking fitting with a crush washer or similar "seal" has a good chance of NOT leaking if it is tightened. Head gaskets? Never seen tightening the head bolts/studs fix a head gasket leak.

Marcb · Mar 20, 2021

Deckard said:
Looks like my garage. Jeep Cherokee, stash of toilet paper.

The Jeep is an American Motors 1980 Cherokee Chief with just under 500,000 miles. It is in pristine condition too.

concours · Mar 20, 2021

450K on the Cdo.... hard to believe.

Marcb · Mar 20, 2021

Looks like it just came off the showroom floor. New tank and pipes. That's about it.

Torontonian · Mar 20, 2021

concours said:
450K on the Cdo.... hard to believe.

Hmmm... I've purchased Commandos cheap where everything was worn out toast at 10 ,000 miles-15,000 or so.
That's if the odometer still worked.

mean gene · Mar 20, 2021

I know I'm a smart ass but 450,000? Better call Guinness Book of World Records!

Marcb · Mar 20, 2021

mean gene said:
I know I'm a smart ass but 450,000? Better call Guinness Book of World Records!

Good thing you're a smart as cause I'm a dumb ass. The correct mileage is just under 50,000 miles. Sorry about that.

click · Mar 21, 2021

Marcb said:
I'm the 3rd owner. Bike has 450,000 miles on it. Previous owners took good care of it. It looks brand new.

Hi,

Is this the same Commando you picked up in 2016?

Marcb said:
Good thing you're a smart as cause I'm a dumb ass. The correct mileage is just under 50,000 miles. Sorry about that.

Good to know, I had a draft message ready to send to you with about a million questions asking how the bike was running after so much milage, I thought you had figured out some super secret for keeping a Norton running with minimal maintenance

Lovely bike all the same, credit to you.

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