Author Topic: Chromed Cylinders Question (Read 5515 times)

mlinder · « **on:** July 20, 2007, 06:38:45 PM »

So, I've got this 67 Bridgestone Dual-Twin 175 SR.
The cylinders (the inside) were chromed, at the factory. Apparently to reduce friction.
I need to have the cylinders rebored.
Does it make sense to have them rechromed, (they aren't sleeved, they are just aluminum), or could/should I have them bored larger adn sleeved with steel, or what do you think?

scunny · « **Reply #1 on:** July 20, 2007, 06:42:39 PM »

bores were chromed to reduce friction and have extended life, if you can have them bored the rechroming might bring them back to the standard piston size

mlinder · « **Reply #2 on:** July 20, 2007, 06:47:34 PM »

Quote from: scunny on July 20, 2007, 06:42:39 PM

bores were chromed to reduce friction and have extended life, if you can have them bored the rechroming might bring them back to the standard piston size

Cylinder 2 was scored. More like gouged, actually. I think it's going to have to go a bit bigger (at least to the point of getting rid of the scoring). I'm going to have to have pistons made anyway, so I could go a bit bigger, and make new pistons, and still chrome the new bore.
Would chromed cylinders be notably better than steel sleeves?

scunny · « **Reply #3 on:** July 20, 2007, 06:58:15 PM »

I don't know about better. I think the rings are a different composition for chrome bores than steel. I would hate to put you wrong, my poor ole brain is pretty mushy these days

I would ask the machinest who is going to do the work. as a side note my isuzu suv has chrome bores and they did this so only the rings have to be replaced

mlinder · « **Reply #4 on:** July 20, 2007, 07:08:46 PM »

Quote from: scunny on July 20, 2007, 06:58:15 PM

I don't know about better. I think the rings are a different composition for chrome bores than steel. I would hate to put you wrong, my poor ole brain is pretty mushy these days
I would ask the machinest who is going to do the work. as a side note my isuzu suv has chrome bores and they did this so only the rings have to be replaced

Interesting. I wonder why more engines dont have chromed cylinders if it has much of an advantage. I'll look into it. If worse cones to worse, I can have sleeves made and have them chromed.

scunny · « **Reply #5 on:** July 20, 2007, 07:17:10 PM »

don't trust me, I've got my forks in the oven

good luck

CrisPDuk · « **Reply #6 on:** July 20, 2007, 07:48:04 PM »

Quote from: mlinder on July 20, 2007, 07:08:46 PM

Quote from: scunny on July 20, 2007, 06:58:15 PM
I don't know about better. I think the rings are a different composition for chrome bores than steel. I would hate to put you wrong, my poor ole brain is pretty mushy these days
I would ask the machinest who is going to do the work. as a side note my isuzu suv has chrome bores and they did this so only the rings have to be replaced
Interesting. I wonder why more engines dont have chromed cylinders if it has much of an advantage. I'll look into it. If worse cones to worse, I can have sleeves made and have them chromed.

1 - Steel liners are considerably cheaper, a major influence when you are mass producing.

2 - If you are going to go to the expense of plating the bores, Nickasil(sp) is better

Uncle Ernie · « **Reply #7 on:** July 20, 2007, 08:43:42 PM »

Older Guzzis have chromed jugs and it seems controversial to me. Some people hate it because once something starts to go, the chrome peels into the engine or something. I would ask this at some Guzzi websites.

I hve some BMW jugs with nikasil in them and I hate it. That stuff is so hard I don't think my rings ever seated. I use too much oil in that bike. Just my 2 cents.

CrisPDuk · « **Reply #8 on:** July 20, 2007, 10:10:22 PM »

I would agree with you Ernie, the benefits for road use are debatable at best, especially when traditional rings are used.

Both Chrome and Nikasil plated liners were originally developed for racing purposes, the chrome by one of the Italian bike manufacturers (MV, I think?), and nikasil by Porsche for the 908/917 programme, the reasoning was the same for both - better heat dissipation on air cooled barrels, which in turn meant you could make the engine significantly lighter.

mlinder · « **Reply #9 on:** July 20, 2007, 10:28:41 PM »

I should mention that this will be a dedicated vintage road race bike. It will never be ridden on the street.
It was a factory race machine. Never been titled or anything. Was used for flat track/scrambling racing. Converting to roadrace.
Still plate it, or go with steel liners, in this situation?

Jugghead · « **Reply #10 on:** July 21, 2007, 12:20:30 AM »

Not sure if this will help or not, but here is another instance of plain steel vs. chromed / light use v. rigorous use
gun barrels.

seriously! imagine the barrel as your sleeve and the bullet as your piston.
most barrells are simply rifled steel, and last a long time just fine from the occassional plinking or hunting.
one of the only chromed barrels I know also belongs to the most durable gun I know, the kalashnikov (AK)
this gun was designed to have an extremely long service life and withstand thousands upon thousands of rounds of fully automatic fire ripping through the barrel.
lets make the SAT analogy... street riding: casual target shooting :: motor racing : sustained fully automatic fire
now, which rifle barrel do you want?

mark · « **Reply #11 on:** July 21, 2007, 01:34:49 AM »

My $0.02.......
The cylinder manufacturing process:

Chrome jug...... (1)cast jug (2)bore to size (3)plate cylinder (4)hone cylinder?. done

Sleeved jug...... (1)cast sleeve (2)rough machine sleeve (3)place sleeve in mold (4)cast jug (5)bore to size (6)finish hone. done...... or make sleeve and jug separately then put together.(I've never seen a 2 stroke made with loose sleeves though)

now which one sounds cheaper?

A plated bore will outlast bare aluminum but sleeves are forever.

BTW...... The AK was a rugged piece, designed to function under the worst conditions.The bore was plated to deal with corrosive ammo and less-than-perfect cleaning.

Happy trails.

Bob Wessner · « **Reply #12 on:** July 21, 2007, 02:35:39 AM »

Quote

one of the only chromed barrels I know also belongs to the most durable gun I know, the kalashnikov (AK)..

The M-16, beginning with the M16A1 model also had chromed chambers and bores.

CrisPDuk · « **Reply #13 on:** July 21, 2007, 03:20:26 AM »

Quote from: madmark73 on July 21, 2007, 01:34:49 AM

My $0.02.......
The cylinder manufacturing process:

Chrome jug...... (1)cast jug (2)bore to size (3)plate cylinder (4)hone cylinder?. done

Sleeved jug...... (1)cast sleeve (2)rough machine sleeve (3)place sleeve in mold (4)cast jug (5)bore to size (6)finish hone. done...... or make sleeve and jug separately then put together.(I've never seen a 2 stroke made with loose sleeves though)

now which one sounds cheaper?

Sounding cheaper and being cheaper are two different things

By the time you factor in the costs of owning and running a dedicated plating shop, as well as the additional quality control systems involved in getting the thin plated wall within tolerances the costs increase sharply

Also against that sort of specialist requirement machining and casting some aluminium and steel comes cheap, especially in quantity.

mlinder · « **Reply #14 on:** July 21, 2007, 07:38:13 AM »

Quote from: CrisPDuk on July 21, 2007, 03:20:26 AM

Quote from: madmark73 on July 21, 2007, 01:34:49 AM
My $0.02.......
The cylinder manufacturing process:

Chrome jug...... (1)cast jug (2)bore to size (3)plate cylinder (4)hone cylinder?. done

Sleeved jug...... (1)cast sleeve (2)rough machine sleeve (3)place sleeve in mold (4)cast jug (5)bore to size (6)finish hone. done...... or make sleeve and jug separately then put together.(I've never seen a 2 stroke made with loose sleeves though)

now which one sounds cheaper?

Sounding cheaper and being cheaper are two different things

By the time you factor in the costs of owning and running a dedicated plating shop, as well as the additional quality control systems involved in getting the thin plated wall within tolerances the costs increase sharply

Also against that sort of specialist requirement machining and casting some aluminium and steel comes cheap, especially in quantity.

ok... so.... now you all have me confused... I guess I'll talk to a machinest to see what they can do.

Dave K · « **Reply #15 on:** July 21, 2007, 10:02:08 AM »

Here is a very good place to ask that question. http://autos.groups.yahoo.com/group/Bridgestone/ As a Bridgestone nut, they would be chromed for me. Yes, the chromed bores used iron rings, the iron bores, used chrome rings. Porsche also used chrome bores.

crazypj · « **Reply #16 on:** July 23, 2007, 06:42:14 AM »

Just get it re-plated. Use one of the newer processes (technology has moved on since the 60's)
The plating is mainly to assist heat transfer, heat gets into main body more efficiently and you don't have problems with different expansion rates. Its not going to be too expensive as plated bores have now been around for a relatively long time.
All new sport bikes use plated cylinders and MX bikes have used them for at least 25yrs
PJ

mlinder · « **Reply #17 on:** July 23, 2007, 10:28:18 AM »

Quote from: crazypj on July 23, 2007, 06:42:14 AM

Just get it re-plated. Use one of the newer processes (technology has moved on since the 60's)
The plating is mainly to assist heat transfer, heat gets into main body more efficiently and you don't have problems with different expansion rates. Its not going to be too expensive as plated bores have now been around for a relatively long time.
All new sport bikes use plated cylinders and MX bikes have used them for at least 25yrs
PJ

I believe we are only allowed to use period-correct processes. But yes, I will go with a coating.
I am worried about heat transfer, because I plan on building the engine to work outside of manufacturer specifications. I will be going with higher compression pistons and con rods which should allow me to handle rpms well above the 11.5k rpm redline.

crazypj · « **Reply #18 on:** July 24, 2007, 06:32:23 AM »

I think even AHRMA knows its going to be difficult or impossible to get chrome plated cylinder so you may have to get a newer process. (its a plated cylinder, the reality is to prevent people plating cylinders that were originally cast iron or cast iron liners, that would be cheating)
PJ

dusterdude · « **Reply #19 on:** July 24, 2007, 08:54:10 AM »

sleeve it,have moly filled rings made for it.

mlinder · « **Reply #20 on:** July 24, 2007, 09:54:40 AM »

Quote from: dusterdude on July 24, 2007, 08:54:10 AM

sleeve it,have moly filled rings made for it.

Well, remember, this is an aircooled 2 stroke. I AM worried about heat transfer, especially at the rpms we'll be running it.
It makes sense that an unsleeved bore will transfer heat better to the cooling fins than a sleeve.

Dave K · « **Reply #21 on:** July 24, 2007, 02:57:48 PM »

Chrome plating the bores is a common thing among Bridgestone restorers. Go to the website I posted and ask where.

bryanj · « **Reply #22 on:** July 25, 2007, 06:40:40 AM »

You CANNOT just bore and run on the ally it simply wont work;

If you use a coated cylined you have to use plain cast rings NOT coated (chrome or otherwise) as you must not run two hardened surfaces E.G. cam followers are hardened, cams are soft (meonitic cast)

mlinder · « **Reply #23 on:** July 25, 2007, 07:24:40 AM »

Quote from: bryanj on July 25, 2007, 06:40:40 AM

You CANNOT just bore and run on the ally it simply wont work;

If you use a coated cylined you have to use plain cast rings NOT coated (chrome or otherwise) as you must not run two hardened surfaces E.G. cam followers are hardened, cams are soft (meonitic cast)

Right, figured that one out. And, the more I learn about this, the more I realize I'm going to have to have really good heat transfer.

bryanj · « **Reply #24 on:** July 25, 2007, 08:52:52 PM »

Don't feel too bad about taking time to figure it out!!
Suzuki used to make a 250cc single cylinder trail bike(TS250) and when they got to the last model (B i think) a customer of the local main Suzi dealer (who happened to be a moderate name in trials competitions)forgot to put TT oil in the tank and seized the piston, Now dealer goes to parts book and finds that the A & B model only lists standard pistons & rings so knowing the bore is the same he orders up a 0.25mm O/S kit for a K/L/M model and re-bores the barrel to fit not noticing when he is boring it that he has removed the hard lining and is boring ally.

Rebuilds engine and is surprised when it seizes solid after a couple of minutes running!! So bad he has to fit new crank as well as the new barrel/piston and the new head.

Moral is "ALWAYS ask if you ain't sure and weigh carefully the answers"

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Author Topic: Chromed Cylinders Question (Read 5515 times)