Author Topic: cross hatch the chrome cylinders upon rebuild?  (Read 4356 times)

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Offline jjwithers

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cross hatch the chrome cylinders upon rebuild?
« on: July 09, 2015, 11:29:19 PM »
I am working with a local 2 stroke guy on having my 175 engine rebuilt. 

The cylinders have some indications that the piston sat for a while but overall, they are OK. 
I am going to get a new set of rings for the pistons.   

He mentioned doing a light hone on the cylinder to get the cross hatch texture on the cylinder wall (like Harleys, BMWs, etc...).

But being that they are chrome, i wanted to check here first and make sure that will be ok?

1967 175 HS
and some BMW's from the 60's and 70's

Offline hardy

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #1 on: July 10, 2015, 07:16:25 PM »
My bs350 had some hone marks visable in the barrels. Not sure of the history of the motor.

Perhaps a more knowledgable bs tech can chime in?

Offline slawsonb

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #2 on: July 10, 2015, 10:29:15 PM »
If the bores are still in good condition with no gouges or scores, I would do as little as p0ssible to clean them up. Some mild polish on a rag to remove any rust or carbon that is left after a period of sitting would be adequate in my opinion.
...bert

Offline BS Mechanic

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #3 on: July 10, 2015, 11:01:33 PM »
I don't believe you should do anything to the chrome bores.  In general, the chrome bore/cast iron ring combination used in the 175, 350 and other BS models function like the more typical cast iron bore/chrome ring combination, except the surface finishes are reversed. 

You want the hard chrome bore to be as smooth as possible for the softer cast iron rings to slide on.  Scratching the hard chrome up will just accelerate wear of the piston and rings.  Depending on how the bores look, the most I'd do is polish off any corrosion or staining from the pistons sitting in them,  but nothing more aggressive.

Anyone else want to chime in with their thoughts?


Offline BRT-GTR

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #4 on: July 11, 2015, 06:07:09 AM »
           You will see references to the honing of chrome bores. I have a pair of replated barrels that do show cross hatched honing marks. See also the link below which refers to honing towards the bottom of the page.           http://www.usnicom.com/

    But in these cases the honing is done to true up replated barrels for roundness and straightness and remove any plating high spots. Original BS barrels with only light use/wear will sometimes show faint signs of honing for the same reason.

      I completely agree with  BS Mechanic and Bert, do not hone the chrome barrel, just clean it up, it has already bedded in.     Steel or cast iron  barrels are honed to take the glaze off and help the rings bed in on the bore but as BS says our engines are reversed, the new rings will do the bedding in.
    Brian.
Growing old is compulsory, Growing up is optional.

Offline jjwithers

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #5 on: July 11, 2015, 02:38:03 PM »
Thanks Guys.  On my parts hunt I ended up speaking to somebody who has restored these bikes and he said the same thing.... do NOT hone them...
1967 175 HS
and some BMW's from the 60's and 70's

Offline nate goralczyk

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #6 on: July 11, 2015, 03:31:25 PM »
Here is a picture of my replated cylinders showing the cross hatched honing as BRT-GTR was speaking about. But as is original chrome cylinder should NOT be honed.

Offline slawsonb

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #7 on: July 11, 2015, 04:21:58 PM »
Nate, is the plating in you pic nicasil?
...bert

Offline nate goralczyk

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #8 on: July 11, 2015, 04:42:50 PM »
Yes that would be correct, had them plated in nicasil by millenium technologies and I must say I'm pretty satisfied with the results

Online dcr

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #9 on: July 11, 2015, 06:13:24 PM »
Using NOS aluminum piston with Niaksil?
1966 175 DT and 1968 350 GTR

Offline slawsonb

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #10 on: July 11, 2015, 06:47:03 PM »
Thought it looked like a millennium job. Had some done recently by them as well and am very happy with the results (especially considering how they looked before they were repaired and plated). I am using NOS pistons and rings.
...bert

Offline Mopar392

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #11 on: July 12, 2015, 10:42:39 AM »
US Chrome does an excellent job as well, did both jugs on one of my 350's, perfect work. Repeat, do not hone chrome, nikasil plating.
DL

Offline Mopar392

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Re: cross hatch the chrome cylinders upon rebuild?
« Reply #12 on: July 12, 2015, 10:42:59 AM »
US Chrome is in Wisconsin and has been around for years.
DL
« Last Edit: July 12, 2015, 11:12:14 AM by Mopar392 »

 


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