Are boring bar witness marks in cylinder cosmetic?

[outasite]

You cannot! do a proper job of finishing after a boring,with a dingleberry brush.And need to be .001to.0015 small to get a clean finish.

[TEXAS20225]

X2

[Umassot50]

Sounds like shoddy work.

[flabum1017]

Basically, without doing a proper hone job with a rigid hone, all the grooves by the boring bar will remain (spiral pattern all the way down). A rigid hone is necessary to get rid of that spiral and make a good cross hatch which the oil adheres to. Without proper machine work, you may as well run no oil.........

[H2OPERF]

boring right to spec is ok when everythings perfect, .0055 at the top doesn't mean you have it at the bottom where it can be a pain to cut.

[Dave Strong]

And ya just don't use any oil when honing.

Dave

[outasite]

A couple of after thoughts,I am supisous of the champher not being adequate after the rebore,many times I've seen the ring chew away at the top of the port,and the shards start a galling the cylinder.The other thing,as the builder,I know it's easy to assume that everything is as it should be but the only way to know is to check it yourself.Borrow some measuring tools or whatever it takes,but make sure in your mind that it's right before assembly.Same goes with the crank and rods,measure twice.Assemble once.

[Dave Strong]

A couple of after thoughts,I am supisous of the champher not being adequate after the rebore,many times I've seen the ring chew away at the top of the port,and the shards start a galling the cylinder.The other thing,as the builder,I know it's easy to assume that everything is as it should be but the only way to know is to check it yourself.Borrow some measuring tools or whatever it takes,but make sure in your mind that it's right before assembly.Same goes with the crank and rods,measure twice.Assemble once.

So true we are all human and can make a mistake, always recheck and conferm its right.

Dave

[powerabout]

A couple of after thoughts,I am supisous of the champher not being adequate after the rebore,many times I've seen the ring chew away at the top of the port,and the shards start a galling the cylinder.The other thing,as the builder,I know it's easy to assume that everything is as it should be but the only way to know is to check it yourself.Borrow some measuring tools or whatever it takes,but make sure in your mind that it's right before assembly.Same goes with the crank and rods,measure twice.Assemble once.

thats why you do a few passes with the ball hone after the boring or do by hand as mentioned above

[Dave Strong]

thats why you do a few passes with the ball hone after the boring or do by hand as mentioned above

Comes back from the machine shop you don't touch it with a hone. Get out the bore guage and mikes and check it if it ain't right send it back. You touch it your screwed.

Dave

[FMP]

A couple of after thoughts,I am supisous of the champher not being adequate after the rebore,many times I've seen the ring chew away at the top of the port,and the shards start a galling the cylinder.The other thing,as the builder,I know it's easy to assume that everything is as it should be but the only way to know is to check it yourself.Borrow some measuring tools or whatever it takes,but make sure in your mind that it's right before assembly.Same goes with the crank and rods,measure twice.Assemble once.

You have got that right,
Had a block done a while back, got it home measured the bores , shaped liked an hour glass and worse. Not even blind holes, and proper cross hatch was not even to the top of some bores. I thought a drunk had done it in the dark. Bad work can happen, and will. Shouldn't happen at all to anyone , but on the water and have a new build do that. Words may not help.

[powerabout]

Comes back from the machine shop you don't touch it with a hone. Get out the bore guage and mikes and check it if it ain't right send it back. You touch it your screwed.

Dave

What I meant was the ball hone comes after the boring and before the hone stones unless you want to run your rings past the razor sharp port edges.

[Dave Strong]

What I meant was the ball hone comes after the boring and before the hone stones unless you want to run your rings past the razor sharp port edges.

I hear what your saying, best deal is send the pistons and them fit to properly honed cyl's. The only thing you should have to do is fit rings.

Might just be me but thats the way I like it.

Dave

[SunDaze]

Guys, thanks for the input. It is pretty clear to me now that the machine work was not done properly and while it may not be the only factor which drove the #2 piston to badly scuff, proper machine work is the foundation upon which a successful rebuild depends. I think the ability to hold oil on the cylinder walls was somewhat compromised by this improper machine work to the point where there was no buffer left for anything else to be even slightly wrong. The brand new air injector confirmed by Brucato after the fail to be about 2% lean at WOT was probably enough of an additional aggravation that when coupled with the improper cylinder topology impacting oil retention, the failure was bound to happen.

The shop I used says they do a lot of "blind hole 2 strokes". Primarily bikes but a fair amount of outboards. The owner told me he cut his teeth as an aircraft mechanic, said he has been doing this for 42 years. I did not detect any deceit but it is clear to me now he is not doing things the right way. He offered to redo the block for $0 but I will not be taking him up on that offer. Perhaps my first clue that should have rung my alarm bell was being told after they had the block that they had never done an Optimax block before. I deliberately sourced both the block machine work and all rebuild components through the shop so they could set up the correct relationship between the pistons and the cylinders.

I live in Binghamton, NY area (upstate New York) and was not able to locate an experienced outboard block machine service locally. I ended up sending this all the way down to Orlando, Florida thinking this shop was in a high boating area with a lot of outboard experience. Lesson learned. Thanks to you guys I now know the questions to ask prior to trying this again as well as some additional checks I can do (or have done on my behalf by a 3rd party) prior to assembly. What is especially insidious about this is that as long as the boring bar work was done correctly and produced a good true shape, a casual check with snap gauge of the bore diameter would not likely find a gentle .0002" undulation from the boring bar. The cross hatch pattern from the ball hone really obscured the improper procedure used by the shop. So, while having the right gauging to at least check the basics is always a good thing, knowing the shop does things properly is even more important.

If anyone knows of a quality shop in my area they think I should check out, please pass it along. I bought my new long blocks through a shop named Marine Power Service in Farmingdale, NJ. My wife drove there and back to get the blocks (5 hours each way). She reported back that they were quite a large operation with a huge machine shop. Does anyone have experience with them on block machine work?

Best regards to all.

[Da Bull]

I hear what your saying, best deal is send the pistons and them fit to properly honed cyl's. The only thing you should have to do is fit rings.

Might just be me but thats the way I like it.

Dave

Winner Winner chicken dinner. You hit the nail on the head. How can a machine shop size a cylinder to a piston if they do not have said piston in hand??? Can`t be done! New pistons are not that perfect. Each and every one must be measured.

DB