Deglazing cylinder walls

The barrells of my 74 commando 850 have a bit of a ridge at the top Cylinders are in spec and I want to deglaze before putting new rings on pistons . Can I deglaze with the ridege or does it need to be removed ? I can just feel the ridge with my fingernail bike has 13000 miles on it . Would appreciate any input on this
Thanks Drummer 99

The ridge would be best removed if you are fitting new rings.
If they meet it anywhere, broken rings is the sure result.

I have used a sharpened triangular file to simply scrape away such a ridge. (Its quite difficult to machine it away, over such a short distance ?)
If done carefully and neatly, and not go too deep.
And then lightly honed to break the glaze.

A good engine reconditioner should be able to remove the ridge and hone the bore.

http://www.ebay.com/bhp/cylinder-ridge-reamer

Tough call ,I'll go out on a limb here to say generally speaking Commando pistons and rings don't wear out given regular quality oil changes. Is the real concern here smoke because it's usually valve guide wear that should be addressed or intake valve seals that have petrified with age or a guide rocking loose in head. That mileage for ring replacement I can't see much why. If clearances measure good put her back together and check the head or even headgasket for leakage evidences. If it's not smoking then save your money and not fret about the ridge .I'm gonna get in hot water for that bit of advice.

Time Warp said:

http://www.ebay.com/bhp/cylinder-ridge-reamer

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Plenty of skill needed with those things.....

Torontonian said:

Tough call ,I'll go out on a limb here to say generally speaking Commando pistons and rings don't wear out given regular quality oil changes..

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Gee, I removed the (slight) ridges out of the bore on an 850 that had only done 12,000 miles, and was then only a few years old, prior to reringing it.
As far as I know, it had had its oil changes done (and the filter wasn't the oem one!) from new..

The rings were quite worn out - big end gaps, lost tension, and even looked a little thin in places.
Long stroke engines aren't generally known for long ring life.
Beats me how someone could get 100,000 miles out of these, the quality must have improved somewhere along the way...

Oils ain't what they used to be, either ??

Since this is a 850 thread.
My 850 is up on the bench,stopped at the six start drive nut,even the air impact won't move it at this stage.
The bore has no ridge at all (20000+ miles) and still on standard pistons which was a pleasant surprise,the pistons need to be checked but am thinking also hone and re re ring or maybe even drop a set of new pistons in along with a check of the crankshaft and a new set of shells (mains if needed)
The crank must have close to a mm of end float.
Wet chambers look to be guides.

The oil pump studs came out along with the nuts,both stud holes have heli coils by the look of it,is that a factory fitting,I can't see even the most ham fisted Norton mechanic stripping a thread that had a stud. ?

Time Warp said:

Since this is a 850 thread.
<snip>
Wet chambers look to be guides.

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Check that its not just inlet guide seals. ?
The seals can sometimes have a shorter life than the guides.... ?

If the oil rings have lost tension, could be oil rings too.

So,is it smoking or not ? Or maybe inlet valve seals hard as rock. Popped off or cracked ? Check.

exam pistons, if ok fit in bore for the gap, ~.0045-55", to decide on next bore size up or just touch up-straighten up clean up bore and if std ring set don't show gap narrow enough then order ungapped size and file correct gap. ~.0122"ish. Run good paper filters or put another better filter over k/n type. If pistons good but gap a bit looser than .0055" then might have knurled to last at least as long as rings to check in and decide next expense or not.

According to the NOC Commando notes you get 2 sets of rings per bore, my own experience confirms the rings do wear out before the bore and on my std bore I am on the second set of rings with the original pistons. Symptoms were blue-smoke out the the timing side exhaust on acceleration, the guides were fine and the new rings sorted the smoke.

look at your piston skirts , are there signs of blowby ?
i would NOT remove these edges at the top of the bore as they act as a sort of seal . i know this may sound daft but in my experience each time i did remove them blowby or blue smoke was the result
if your rings are a bit worn , change them but as you use the same pistons , the exact location of the rings will not change and thus broken rings are impossible (impossible on a norton ??????????????)

those grindstones used to deglaze are only good for ruining your walls , i found out the hard way
i got such a device FREE for anyone willing to fuck up their bores

Rohan , 100000 miles on one set is probably a bit of wishfull thinking , 40000km sounds about right for roadwork,racing is a bit shorter lifespan

Some of the ridge you feel may be carbon, ensure you've got rid of that first.

Whether or not to remove the actual step or not is a matter of debate, I would imagine that in doing so, you are highly likely to remove metal in an imprecise manner and over do it, make it oval etc.

For de-glazing, I have used a large flap wheel for this before with perfectly satisfactory results... yes, I know it wouldn't have been properly cross hatched etc, but it worked perfectly nonetheless!

After MANY years of auto engine building, I cannot imagine doing bore work on an engine and not removing the ridge. There are tools specifically for that purpose that are easy to use. Not removing the ridge can easily, as noted in a previous post, cause a ring or piston land to be broken. The ridge should be removed and the cylinder will then need boring/honing, most likely to the first (or next) standard oversize which will require pistons for that size. If there is a ridge, the bore is now worn by that amount - and tapered as well. If there is no ridge, a bore can be honed to remove the glaze and new rings of the same size installed though taper should be checked. A tapered bore will cause oil burning/low compression because the rings can't seal properly in a tapered bore - they can only fit/seal properly with a bore at the correct diameter for the rings. In a tapered bore, the rings will only seal correctly at the bottom (non-tapered) portion of the travel, which is the least important part of the stroke.

Drummer99 said:

The barrells of my 74 commando 850 have a bit of a ridge at the top Cylinders are in spec and I want to deglaze before putting new rings on pistons . Can I deglaze with the ridege or does it need to be removed ? I can just feel the ridge with my fingernail bike has 13000 miles on it . Would appreciate any input on this
Thanks Drummer 99

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This is one of those jobs which needs to be measured accurately before proceeding any further - see if olchris will lend you his tape measure :lol: :lol: :lol: :lol:. Or take it to a reputable re-borers for checking if you don't have a bore gauge. Strange there's a ridge but only 13,000 miles use.

Here is a little clip of my pal Pete and I using a "Ridge Reamer" on aTriumph barrel

http://s136.photobucket.com/user/philly ... 1.mp4.html