A Good Ride Spoiled

Tornado said:

Just a bit worried of damaging the alu head under the spacer/washers?

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I don’t think it would cause any damage, but Glen is right, a bit of hardwood and some large washers and you’ll be fine, it is not such a high torque after all. Doing it without the head will be easier I’d say.

Bore pics:




Cant see any scuffs or feel any lumps, except at very top where carbon is built up.

Not to be Mr Tedious but pull the jugs now not later. Better now. Measure them up. Measure up the pots. Check the rings. Pull the valves check that stuff. Apart means you can look into the bowels too.
Best to know, not hope.

You could clean the old gasket a bit and lay it in there for the thread test. Yes, I would bolt it right up as per the manual. Mine failed this test. The fix has been good though (15 years and 26,000 miles) and it wasn't awful to do.

The bores look good. There are some very faint vertical lines but those are pretty standard for any engine that has run more than five miles.
At least they appear to be faint lines from here.
Separate issue, you might pour some gasoline or solvent in behind the valves to see if they could use a lap.

I had a similar gasket / smoke issue a year ago. Decided to pull cylinders since i was already in. Very easy to do. Hone job, new rings, new seals, new head gasket. Great opportunity for clean and paint also. Doing it with an experience member of our club made it easy. Bike started and ran like a champ all summer. Still getting some smoke though. Going back in soon.

Seems there are couple of good recommended machine shops in region for skimming/honing services.

In the last bore pic, is there much concern of the circular "center punch" mark on the A piston? Has slightly raised ridge around it. Damage from something or a factory thing?

Torry .... you got this , from what I have read so far on your threads , you can get this done no problem ... yup you have not done this before , so just go easy taking your time .... then put that feather in your cap .... not like it mid season and you don’t have another ride .... enjoy the Triumph on nice days then work on the Norton when it not ride weather , will surprise you how straight forward this process is .... in for penny in for pound , right .... enjoy the learning curve !

I recall kicking this bike over when you first got it and it had full compression. It's not a tired engine needing everything. That's why I would go minimal, but with the leakdown test after assembly.



Glen

There doesn't appear to be ridges in the top of the bores, but they have done a lot of miles. Pull the pistons, biff them and fit new Emgo pistons. Mine cost me approx $300.00 NZ about 8 years ago.
Don't fit new rings to old pistons. When rings wear, so do piston ring lands. It used to be that when re-ringing British cars, we would get the machinist to clean the top ring grooves up on a lathe and fit new rings with special ring spacers on top of the top ring. I would not ever do that with a Commando engine. Besides, the cost of doing the work on the pistons would probably equal the cost of the new pistons. [ I rebuilt lots of car engines in my younger days. Mini's to Jaguars. ]

Ages ago, when fitting my head on my 850, i torqued the head bolts etc up but the two nuts under the exhaust started pulling out. It was a fuck it moment so decided just to ride the bloody bike. It never gave me problems.

Later, when fitting the new pistons, I fitted helicoils to the head. I have reused that copper head gasket twice now and my secret was to wipe the meerest film if automotive silicone on both surfaces before fitting, and fit it exactly the same way it had been originally. I have never had any significant problems with oil leaks from that area in all the time I have had the bike. [ well since I have worked on it anyway.]

Tornado said:

Ha! Thats what I just did the decarbon scraping with. Had a bit of soft alu scrape stock, already with a 90 deg bent at end. Worked fairly well.
I can now read "STD" on rhs can, as well as "A" , "RF" and "ID 66" on that can.
Other side has "LF" , "B" , "ID 13" , and barely visible "S". Cannot make out a full STD that side.
Do these markings mean standard size, not oversized? Do the ID's inform anything useful?

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LF: Left Front, RF: Right Front? Stamped during a previous overhaul?

Lots of folks wanting to spend your money - LOL!

Those cylinders look good. Can still see cross hatching at the top, so they are not worn at all. Like Glen said, do a gas test on the valves, lap if required, check the head threads and button her up with a new head gasket.

When checking the head threads, best use a deflection beam style torque wrench - that way you can watch the torque rise (or not) as you tighten the nut. If the nut turns and the needle stops rising, then you have a thread that is pulling out. The middle one at the back is the worst for it in my experience.

An old piston ring works well to measure bore wear.
On the other hand, I doubt that you have measureable wear with hone marks still showing.

Glen

Clean it up, new head gasket, check to see if the valves are sealing and put it back together, the bores look good rings have bedded in so no need to replace the rings or pistons, make sure the head is flat, as for head gasket it will be your choise in what you use myself use copper head gasket had 2 flame ring gaskets blow, have never had a copper gasket blow this is from my bike I have owned for 45 years and was a everyday rider most of its life with lots of miles on it.
Been getting a bit of oil colour around the rear and side of my head and got my torch out for a closer look at my head gasket and no oil but still looked like a oil leak till I smelled it and its fuel related so when riding it was my intake manifolds leaking, so went and got new manifold gaskets yesterday, so 10 years since I had the head off and just on 30k miles ago, the only time my Norton only smoked was when the original bores wore out from my younger days of flogging my Norton and a bodged up valve giude replacements back in the early 80s, I am still running my original valves in my head today after 45 years.
I call my Norton the freak, its been so good to me in the 45 years of ownership from new and now I give it a lot of respect, its now semi retired just like its owner.

Ashley

I don't think your bore pictures demand that you pull the barrels off,... but pulling the barrels and reinstalling them is not a hard task to perform. If you pull them, then you get to eyeball the cam lobes and the followers to see how well they are mated. You also get to feel the amount of play on the big ends of the rods, and wash the pistons clean of any carbon particles so the rings are floating correctly in their grooves... and not stuck...

It's not a difficult process at this point to pull the barrels and then reinstall them after you inspect and clean the pistons, just protect the connecting rod shafts with cardboard to keep them from getting any hit, nicks, or scratches on them. I had to pull my barrels 2 summers ago when I lost a stellite pad off one of my followers... It's pretty straight forward. You'll be happy you took a look... IMO

Got a rough quote on following from locl motorbike specific machine shop (Mongoose Machining) with a good rep (in CDN dollars of course):

"Depending how much we are taking out, the price would be roughly $150-200 to machine both the head and cylinder surfaces. Cleanup hone $57.50 per hole, re-bore $110 per hole. Pricing is approximate only- accurate pricing will be determined once the physical inspection is complete."

Not much of a shocker....Would be good to get their pro advice on cylinder condition re. out of roundness etc.

Just one last comment, and I am going to leave you to your choice: Did you show the engine shop the pictures of your cylinders?

There is very little cylinder wear (cross hatching is still visible), so they should not be out of round. There is very little cylinder wear, so it will not need a rebore. Using a straight edge and a feeler gauge, you should be able to determine if the cylinders and the head need decking.

Ultimately, it is your bike and your money. I would just hate to see you tear up a perfectly good engine, spend money on parts that don't need replacing, and machine work that isn't required.

And I am out. Best of luck.

You can check for cam wear without removing barrels by measuring lift.



Glen

I shall respect the decision you make as I would expect you to mine, also I wish you well and good fortune on the fixings..... May they be inexpensive, or at least within reason..... I like your bike too.

worntorn said:

You can check for cam wear without removing barrels by measuring lift.



Glen

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I've seen a drive side lobe on a 70 that had pitted hardening face marks on the ramps yet the highest point had no marks at all.

Derek Wilson said:

Just one last comment, and I am going to leave you to your choice: Did you show the engine shop the pictures of your cylinders?

There is very little cylinder wear (cross hatching is still visible), so they should not be out of round. There is very little cylinder wear, so it will not need a rebore. Using a straight edge and a feeler gauge, you should be able to determine if the cylinders and the head need decking.

Ultimately, it is your bike and your money. I would just hate to see you tear up a perfectly good engine, spend money on parts that don't need replacing, and machine work that isn't required.

And I am out. Best of luck.

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That bore looks fine. New head gasket. New guide seals.