To hone or not to hone?

[Keith.owen]

Hi all!
On another topic, this time honing or more exactly de-glazing.

There seems to be a school of thought that a cylinder should be honed to acheive scoring at a 45 degree angle or thereabouts in both directions , clockwise and anti-clockwise to achieve a cross hatch pattern. The theory being that this traps oil and reduces friction.

On the other hand when a cylinder and piston rings are new, they have to be run in, which I guess equates to acieving uniform mating surfaces i.e removing the honing marks (after machining) by running the engine.

There is no reference in any Ariel manuals to honing / de-glazing and in the notes on tuning in Waller it is simply suggested that during running in the barrel is removed and the piston inspected for any high spots that should be taken down. So the question is, in the case of an Ariel with a Cast Iron Barrel, if it's nice and smooth does this mean either that it is a) nicely run in and should be left as is or b) should it be lightly honed again?

I appreciate that materials and production techniques are different these days and that this in itself might call for diferent courses of treatment. Does anyone have any thoughts on this?

Keith

[brenton.roy]

Hi Keith, depending on how worn the bore is, a light hone is a good idea.
I've always thought it improved compression ( but I don't know this for sure).
A glazed bore, even a new one, will pass and burn oil. Unfortunately, I do know this for sure!
regards, Brenton

[Keith.owen]

Hi Brenton,
I thought as much but wasn't entirely sure for the reasons that I gave.

Do you know if the cast iron barrels were lined at the time of manufacture or is the whole caboodle just one casting?

keith

[brenton.roy]

Hi Keith, I've seen a number of posts - particularly from Nev - that suggest they were unlined.
I have a few VH, VB and NH barrels, all sleeved, and I have never seen a cast iron bore. At the rate they wear out, any bike with reasonable mileage would be sleeved.
Brenton

[nevhunter]

Haven't seen an original sleeved, as supplied The 350 barrells are a bit weak and I don't recommend sleeving them if they are worked hard
A freshly bored and honed cyl beds the rings in quickly. The hone scratches take a fair while to dissappear because they are in a surface and that surface has to wear to the depth of the scratches before they disappear. worn and distorted bores may not bed the rings well and may not be really successfull. Honing the bore does remove metal even though it may not be much. You can remove the glaze by using coarse wet and dry with kerosene and a circular motion of the hand. Again if the bore is worn unevenly you are only making it look good. It's still out of shape and there is a limit to what the ring will adapt to. You can have a fair bit of taper ( .003 to .004) and if you remove the unworn ridge carefully so the new top ring won't hit it and break, you can get a few thousand miles extra use. Nev

[Keith.owen]

Hi Nev,
I understand your concerns about the NH barrel being a bit weak (although I hve no experience of this and welcome peoples input). The concern is what to do when the point is reached at which a barrel can't be bored out further (due to non availability of ever greater over-size pistons)? I guess eventually there'll come a point when there are no more barrels to be had!

Is this a known problem or cautionary advice?


Keith

[Simon.Gardiner]

I've had several 350 barrels and a 500 barrel (all iron-head type) sleeved and had no problems. It might depend on the OD of the sleeves - I doubt if any of the ones used for me were 'factory spec', probably the closest of what was available at the time.

I don't find they wear particularly badly, I think the 500 barrel has over 20k miles on it and you can only just feel the start of a lip. Maybe the sleeves wear better than the original iron!

[nevhunter]

Sleeves DO wear at a lower rate than the "as cast" iron as they are centrifugally cast and are a superior metal. They do not contribute to the strength of the barrell to any extent so the remaining metal after the bore is enlarged to accept the sleeve is what counts and sometimes it is just not enough. The 350 cyls were always a problem with running high comp motors on alcohol. It is hard to out a figure on what wall thickness is required but somewhere around .150" of "parent" metal should remain, unless the engine has through bolts I have seeen many engines fail where the cyl has left the crankcase on bikes ridden normally and the damage to the engine can be significant but also the situation of the engine stopping suddenly is also dangerous. Ordinary grey cast iron does not have a very high tensile strength. Nev

[Keith.owen]

Nev,
When the cylinder leaves the crank case where does the failure occur?

Does the barell part company with the flange or what?

Doe this happen just with tuned engines or what?

Keith

[nevhunter]

The flange stays put and they break some where between the flange and the bottom fin.. There is not much metal there even when new but a very thin sleeve is obviously better than a thick one. The fault shows up more in racing where many of the bikes fitted a device to apply a load from the frame to the rockerboxes. Other people have tried through bolting but the closenes of the head bolt holes to the bore makes this difficult. Fitting a thick sleeve and welding it top and bottom can be tried but with the problems of getting the heat from the bore to the fin area ,( IF there is any distortion) as well I am surprised that NEW patterns haven't been made for these. It is not a difficult casting, and the machining is straightforward. The consequences of the cylinder failing are quite dire so it should be treated as a fairly serious matter. Over the years on rallies I have witnessed a substantial number of cylinder failures because of sleeving and the people who do it do not seem to be aware of what they are doing. I have seen cylinders bored out so far that the sleeve is visible between some of the fins at their base. Obviously there is no metal left to take the load. Strong valve springs contribute also and the break is usually on the timing side initially. Off centre boring ( core shift) will make it worse. Some cast iron is stronger than others but it is never a strong metal in tension.. Nev