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ZB 34 barrel question #731697
04/12/18 11:40 am
04/12/18 11:40 am
Joined: Apr 2018
Posts: 10
Warrington England
R
Rob Milton Offline OP
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Rob Milton  Offline OP
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Warrington England
Hi all, I am new to the site and have a ZB 34 alloy motor I want to put together, I think the barrel has had a new liner at some time and would like to know if it should have a shoulder at the top that sits into the cylinder head like the B33 has ? Mine has the liner flush with the top of the barrel.
Any help appreciated.

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Re: ZB 34 barrel question [Re: Rob Milton] #731704
04/12/18 1:42 pm
04/12/18 1:42 pm
Joined: Feb 2012
Posts: 1,273
Middle East,
Kerry W Offline
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Kerry W  Offline
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Middle East,
Many years since I had an early barrel in my paws, but I'd have said 'yes', there should be a spigot at the top, which registers in the head. The head gasket (originally an old style copper/asbestos thing, like a car had) fits around the spigot, providing the oil seal for the pushrod tube and confirms the seal on the compression side - the later bikes use a laminated alloy 'peelable' gasket, that can be peeled down to a thickness a fraction greater than the gap between the head and barrel (where the head rests of the spigot and no gasket fitted - measured with a feeler gauge around the head and barrel faces), so that the top of the spigot almost touches the head (within a couple of 'thou'-ish, depending on how parallel the head and barrel liner faces are). This procedure is described in any literature covering the CB/DB/DBD bikes.

The later gasket should be usable in an earlier engine (pretty sure I've read that on here - I'd certainly be looking at trying it myself), however, even of you were to use an original style composite gasket, there would be a radial gap between the bore and the inner edge of the gasket (where the top spigot should be), creating a space for 'undesirable things' (carbon build-up, hot edges of head and barrel, resulting in erosion and pre-ignition, for a start). If the diameter of the big holes in the gasket is 85mm, then running it with the gasket exposed to combustion is probably OK (cars do it). The problem is finding a gasket where the hole matches the bore of the barrel. There is perhaps an answer..

...which is to use a later style laminated (peelable) 350 gasket..and enlarge the hole to suit the bore of your ZB barrel, eliminating most of the space left by an original gasket with no spigot - however there would be space left formed by the recess in the head, where the spigot registers. Hmm..

So, a spacer - a ring with the bore of the barrel, an OD that was a neat fit in the big hole in the gasket you plan to use and a height just a little less than the thickness of the gasket would do the job of filling the void left by the absence of the spigot and work with stock gaskets (early or late). The head is alloy, so any spacer could be alloy or anything tougher. It would be easy to trial-fit, with studs in the barrel and gasket in place. Small radial alignment errors would nice to avoid, but not be a train-smash for day to day street use.

All this assumes you don't want to replace the liner...something I'd avoid, as the old barrels do seem to crack vertically with new liners if they are the least bit too tight..and never mind the effort and expense.

KW

Last edited by Kerry W; 04/12/18 1:52 pm.

No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: ZB 34 barrel question [Re: Kerry W] #731707
04/12/18 3:04 pm
04/12/18 3:04 pm
Joined: Feb 2003
Posts: 2,951
Ohio
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Rickman Offline
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Ohio
One other thought about a gasket, find someone who makes solid copper gaskets.

I'm sure you will need to make a template of the spacing of everything where this gasket will fit, and after designing this template, take it to the copper gasket maker, along with your desired thickness of copper, they can easily make a gasket to fit.
I'd think a stiff type of paper would work? Cardboard at worst?

They could even make the big hole slightly smaller, so that YOU can definitely file the hole to exact fitment without any ledges to worry about filling.

One thing to worry about, is if the recess for the spigot is still present in the head?
If it is, then I'd think you MUST have a ... spacer? ring? sleeve? made to take the place of the missing spigot...

Last edited by Rickman; 04/12/18 3:07 pm.
Re: ZB 34 barrel question [Re: Rob Milton] #731762
04/13/18 3:33 am
04/13/18 3:33 am
Joined: Sep 2001
Posts: 2,802
Comox BC Canada
G
Gordo in Comox Offline
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Posts: 2,802
Comox BC Canada
Rob

I have what I think is an original ZB34GS barrel and it has a raised spigot standing about 0.114 inches above the main alloy top surface. The width of the spigot is about 0.210 inches. The barrel is at 20 thou over size so a std barrel would be a bit wider. The countersinking in the alloy for the insert is wider than the spigot flange so there is a small groove around the outside of the spigot. My BB34GS barrels look to be about the same.

Gordo


Without frequent roadside repairs there is no fun in riding!
Re: ZB 34 barrel question [Re: Gordo in Comox] #731770
04/13/18 7:45 am
04/13/18 7:45 am
Joined: Apr 2018
Posts: 10
Warrington England
R
Rob Milton Offline OP
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Rob Milton  Offline OP
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Warrington England
Thankyou for all your information, it is as I thought then, it maybe that I can machine the cylinder away to expose the spigot and space the barrel at the bottom as the recess is still in the head to accept the spigot.
Rob.

Re: ZB 34 barrel question [Re: Rob Milton] #731775
04/13/18 10:07 am
04/13/18 10:07 am
Joined: Sep 2016
Posts: 178
County Durham
D
ducati2242 Offline
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County Durham
Id change the liner . Just done mine on my DB34 and it isn't difficult if done correctly .

Re: ZB 34 barrel question [Re: ducati2242] #731777
04/13/18 10:29 am
04/13/18 10:29 am
Joined: Apr 2018
Posts: 10
Warrington England
R
Rob Milton Offline OP
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Rob Milton  Offline OP
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Warrington England
Should it have a composite or copper gasket ? Is one better than the other ? Ducati2422 may be right, it may be best to have a new liner as its bored to plus 60 now, the only down side would be it has a genuine piston in it at present.
Cheers....Rob.

Re: ZB 34 barrel question [Re: Rob Milton] #731985
04/15/18 7:54 pm
04/15/18 7:54 pm
Joined: Feb 2011
Posts: 3,539
Orygone
Boomer Offline

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Orygone
Liners for the long rod barrels will need to be custom made unless you stumble across a pretty much non existent OEM replacement. As Kerry said these old cylinders are brittle and getting the liner to fit is a science. The OEM cast steel liners were made of austenitic steel that has a higher content of carbon. This is so the liner does not expand as much so a low interference fit is used to keep contact between the liner and cylinder at a maximum. Usually the fit is in the .005 to .015 range. The problem today is finding custom liners that are made of austenitic cast steel instead of the normal industry standard of gray iron. Gray iron expands greater so one has to be very careful of the interference fit, hence the cracked liners. If gray iron liners are installed with too little fit then they don't make as good of contact with the liner and you get heat transfer problems. In the past I have contacted Phil Pearson to see if he has any of the longer liners available and while he didn't he referred me to the casting company that cast the blanks for his short rod barrels. Unfortunately, they would need a run of 200 to make it financially viable for them. LA sleeve offers a liner and a service to install but that entails shipping your cylinder to Los Angles.


HTH, Bill B...


BTW, I highly recommend using the peelable gasket. The routine is as Kerry stated and when followed provides the best seal. The procedure is described in "The Gold Star Book" by Bruce Main-Smith.


Boomer
Re: ZB 34 barrel question [Re: Rob Milton] #732195
04/17/18 4:42 pm
04/17/18 4:42 pm
Joined: Nov 2011
Posts: 4,829
U.S.
Magnetoman Online content

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Both steel and cast iron can be produced with an austenitic structure. To add to this discussion, on p.g 28 of 'Goldie' the author writes that "austenitic iron" was used for the barrel, the interference fit was 0.003"-0.0045", and originally it was pressed in with a 2 ton press but in "later years the muff was "pre-heated to 220 oC and the liner pressed in cold."

'Goldie' gives a figure of 18 microinches/inch for the expansion coefficient of the iron (presumably, per oF). Someone who wanted to spend time on this could use this value to narrow down the range of possible compositions that BSA used.

Re: ZB 34 barrel question [Re: Magnetoman] #732219
04/17/18 8:00 pm
04/17/18 8:00 pm
Joined: Aug 2001
Posts: 1,897
Elko, Nevada USA
dave - NV Offline

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Gents .. A hint for you when replacing a liner in a heated cylinder. Be sure to place a heavy weight on the top of the liner lip while the cylinder cools down to prevent the liner from 'creeping up' a few thou. I've used a heavy piece of rail iron that works well. What can happen later is the liner will move down when the muff heats up with a hot running engine and the head gasket may blow out. "BTDT got the shirt". aarrgh

Speaking of liners. I have a very nice used +20 liner to sell. Years ago I was building up my engine and needed a piston. I had bought a selection of pieces from a gent that included a new STD piston I needed and a OEM liner that I used. So, I have another good part needing a new home. How much? $100 sounds fair.

I was always under the impression the characteristics of the austenitic steel liners were it's long wear and the higher rate of expansion relative to iron better maintain liner/muff contact for better heat transfer. BTW, the 3 new cylinders I've bought from Phil Pearson all have austenitic liners.

Another idea for you ... I've been sending Goldie cylinders to Bore Tech for their near perfect bores and feel the added expense is worthwhile. This includes the new 90 bore cylinders from Phil Pearson that he's sent me unfinished. They have a web page on the Net.

Last edited by dave - NV; 04/17/18 8:04 pm.

Dave - NV
Re: ZB 34 barrel question [Re: Rob Milton] #732238
04/17/18 10:48 pm
04/17/18 10:48 pm
Joined: Feb 2011
Posts: 3,539
Orygone
Boomer Offline

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Orygone
When inquiring to Phil Pearson about what liners and what fit to use on my BB34 GS barrel this is the reply I received:


Hi Bill

If the liner is made from the original BSA material = austenitic iron 3-4 thou is fine

Cast iron will become a loose fit when hot unless 6 thou is used which I consider too much of a fit.


Sorry, I interpreted this backwards.



Bill B...

Last edited by Boomer; 04/17/18 10:58 pm.

Boomer
Re: ZB 34 barrel question [Re: Rob Milton] #732241
04/17/18 10:52 pm
04/17/18 10:52 pm
Joined: Feb 2011
Posts: 3,539
Orygone
Boomer Offline

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I used the information for interference fit dimensions off of the instructions sheet that is provided with replacement cylinders in Covmo, Hepolite, and AE which I believe are all the same source and OEM replacement parts.


Bill B...


Boomer
Re: ZB 34 barrel question [Re: Rob Milton] #732304
04/18/18 3:12 pm
04/18/18 3:12 pm
Joined: Feb 2011
Posts: 3,539
Orygone
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Yes Charles, I should have said austenitic iron and not steel.


Bill B...


Boomer
Re: ZB 34 barrel question [Re: Rob Milton] #732328
04/18/18 6:29 pm
04/18/18 6:29 pm
Joined: Nov 2011
Posts: 4,829
U.S.
Magnetoman Online content

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Iron is an element, number 26 of the periodic table, so it would make sense if 'cast iron' would be iron that has been, well, cast in a mold at the factory and hence is close to being pure Fe. 'Steel' has another few elements added to iron, including carbon, to modify its properties so it would make sense if 'carbon steel' has a fair amount of carbon in it. However, despite what might make sense for the names, carbon steel has less carbon in it than "pure" cast iron.

Add a wealth of additional names for specific materials (pig iron, wrought iron, grey cast iron, alloy steel, malleable cast steel, stainless steel, ...) and only someone who worked with all of these materials every day could hope to keep most of the names straight without referring to a book. Further, added to the names of the irons and steels are the names of the microscopic structures within them that significantly determine the macroscopic properties. Austenite, pearlite, cementite, ... And, even then, it's not as if something as specific sounding as "austenitic cast iron" is sufficient to define a material since there are over a dozen grades of it, all with different properties.

Many people have read that Matchless had problems with crankshaft breakage which were fixed when they changed to "nodular cast iron." OK, hands up if you actually know, without looking, what the microscopic structure of nodular cast iron is and what properties it has that might have fixed the problem. For those who have your hand up, keep your hand up if you know, i.e. not just read in a magazine, what specific material a Matchless crankshaft is made of. If you went to a metals supplier and asked for "nodular cast iron" in order to make your own crankshaft they would say there are a dozen materials under that name so "Which one do you want, sir?" The point is, while a term like "nodular cast iron" is knowingly written about, very few people who use that term actually know what it means. Luckily, very few people need to know what it means.

Anyway, if someone contacted a supplier who had Gold Star cylinder liners and asked for one made of 'pearlitic cast steel' they'd either be sent whatever liner the supplier had, or (much less likely) be talked through the differences in nomenclature and then be sent whatever liner they had. Although I'm all for accuracy, the only time "cast steel" vs. "cast iron" would be important in this context is if someone were commissioning a foundery to manufacture a batch of cylinder liners, in which case a lot more information than just those two words would be needed to specify the liners.

Re: ZB 34 barrel question [Re: ] #732350
04/18/18 9:38 pm
04/18/18 9:38 pm
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Magnetoman Online content

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Originally Posted by Charles DB
As we are talking about engineering here it makes sense to at least make an attempt to get the fundamentals right without having to be pedantic.
I'm more of a fan than most of getting the fundamentals right. However, the point of my post was that, in the context of this discussion of liners for ZB Gold Stars, you're fooling yourself if you think typing "austenitic cast iron" (vs. "...steel") counts as getting the fundamentals right since there's a lot more needed to characterize the metallurgy than just those three words convey. And it's not like there's a choice of available ZB liners where using those three words would distinguish between them.

Re: ZB 34 barrel question [Re: Rob Milton] #732451
04/19/18 8:42 pm
04/19/18 8:42 pm
Joined: Jul 2006
Posts: 230
SANTA FE
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bsalloyd Offline

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SANTA FE
There are more grade of austenitic cast iron out there than you can imagine. The are also flake graphite and spheroidal types. The most common ones here in the colonies is Niresist #1, #2, and #3. The percent of nickel added is varied to control the rate of thermal expansion. If you look at Niresist #3 the rate of thermal expansion is 12.4 and aluminum is 13. A pretty good match. I am not sure this is the material that the original BSA engineers specified, but it is a good choice. If anyone finds a source for this material let me know. I would like to make my liners out of the material as it was intended. The rate of thermal expansion for cast iron is between 10 and 11 requiring a greater interference fit to keep it in place. Not a good thing with our thin aluminum cylinders.


1951 ZB GS
1953 BB GS
1953 Super Flash
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1963 RGS


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