? for the experts, horizontal chatter marks in jug

[mtngun]

My 066BB jug has some funny looking horizontal "chatter" marks (for lack of a better term) in at least a couple of places.

I don't know for sure how long they have been there, but I noticed them when I took the jug off to do some modding. Perhaps it came that way from the factory, or perhaps it is some kind of funky wear pattern.

The horizontal lines don't go all the way around the cylinder. You can see how most of the lines terminate about mid-photo.

This is looking through the exhaust port. Sorry for the poor pic, but it's the best I could do without a borescope/camera.

There is a similiar set of horizontal lines about 3/8" above the exhaust port.

If the saw were running satisfactorily, I wouldn't worry about the lines, but compression on this kit has always been pathetic and I'm wondering if these "chatter" lines have something to do with it ?

Anyone seen anything like this before ?

I have a theory, just based on appearances, but I want to see what the experts say.

I'll ask Grande Dog to take a look at it, too. I'm not pointing fingers, I just want to understand and learn.

 

[timberwolf]

Unfortunatly I have seen the same on at least one other BB. Just poor factory honeing in the upper cylinder. Which is where it counts most.

 

[pioneerguy600]

Looks kind of uniform so I would say machining marks from assembly line.
Pioneerguy600

 

[mtngun]

Thanks guys, I respect your opinions. That's pretty much what I thought -- what else could it be ?

If the lines were there when the kit was new, I didn't see them, but they are difficult to see, way up at the top of the jug.

I've been complaining about compression on this kit from day one, and blaming it on the compression ratio, port timing, altitude, etc., etc.. Well, I do think the compression ratio and port timing leave something to be desired, but now I'm wondering if this chatter was the main culprit all along ?

Oh, well, the kit didn't cost much, and it was a good learning experience for me.

 

[mtngun]

Nikasil is hard on bandsaw blades !

However, no sacrifice is too great to further the science of chainsawology.

Remember, this P&C was installed last summer and used hard for milling and nothing but milling. The pop-up and porting were done only recently, as described in another thread.

The lines won't actually catch a fingernail, but you can a feel a washboard effect as you drag your nail over them.

Exhaust side of piston. My camera doesn't do it justice, but the skirt still has 100% of the machining marks. No wear to speak of.

Intake side of piston.

Last compression test was 131 psi.

Thoughts ?

 

[HARRY BARKER]

what brand of kit was it?

 

[mtngun]

what brand of kit was it?

Bailey's. Grande Dog will be over to look at this thread eventually.

 

[pioneerguy600]

What was your ring end gap? I had a new BB kit P&S that the rings were .015 and .016 new from the factory, it went back.
Pioneerguy600

 

[Saw Dr.]

I say put some JB in the grooves, and TIG 'er back up.

 

[blsnelling]

Way to take one for the team!

 

[mtngun]

Way to take one for the team!

It seems to be a habit of mine.

Ring gap ? Kinda hard to measure now. But I believe I noted the gap when I pulled the stock 066BB to install the modded OEM, so it is probably buried in that OEM mod thread. Off the top of my head, I want to say the gaps were 0.010" or less. They were not a red flag, at any rate.

 

[pioneerguy600]

Reminds me of some of the 044 cylinders Lakeside cut up for studyiung the ports.
Pioneerguy600

 

[Grande Dog]

Howdy,
To me it looks like the ridges are square to the bore and not spiral. I'm thinking that the pre-plating hone went to the top of the bore and just stayed there for a moment instead of cycling up and down. I can also see where the bore inspection tool wouldn't detect this.

The bore inspection tool I saw them using looks like a pipe expander. They stick it down in the bore and the feelers are pneumatically expanded and indicate out of round or taper.

The feelers are bars that run the length of the tool and engage the length bore. It would just lay across the high spots and as long they were round and not tapered, it would pass inspection.

I think it's really great that you took the time and energy to do this close of a inspection on this cylinder. I wouldn't have any issue with sending you one of the latest generation kits for your trouble.

Just pm me with your customer number or shipping information, and I'll head one your way.

Also, I was reading your timing of the cuts on the mill. I would have thought there would have been bigger discrepancies between the different top ends. Have you tried running that lo pro on a 404x 8 rim? If you're interested in checking it out, I'll through one them in the box too.
Regards
Gregg

 

[7sleeper]

Howdy,
To me it looks like the ridges are square ........ I'll through one them in the box too.
Regards
Gregg

That is what I call customer service!



7

 

[mtngun]

Also, I was reading your timing of the cuts on the mill. I would have thought there would have been bigger discrepancies between the different top ends. Have you tried running that lo pro on a 404x 8 rim? If you're interested in checking it out, I'll through one them in the box too.
Regards
Gregg

Thanks for your input, Grande Dog. How do you find time to read all of my goofy posts ?

No, I haven't tried your 404 rim suggestion. In fact, I've been running a 3/8 x 7 with it so far -- haven't tried an 8 pin yet, though eventually I'll get around to it. I don't think think the average 066 has nearly enough grunt to mill with an 8 pin, not even wtih low pro.

You are right, the milling speed improvements are pretty trivial compared to say, cookie cutting times done by some of the pro modders on AS. The cookie cutters commonly report 50% or better improvements after a woods port. I doubt if we will ever see that on an Alaskan mill. More like 10%. But I use the saw for milling, so that is how I test it.

I'll pm you about the rest.