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Keith Black pistons not the same size???

Don,
I'm still waiting for the new pistons & have been thinking a lot about this. I'm kicking around running these but my issue is I don't have the high tech tools. At the machine shop the dial bore gauge read consistent at several different positions. At my place I have a .001 feeler tape I can put down the bore in several different places & get a consistent slow smooth drop of the piston. With a .0015 feeler it will stop snug in the bore. With my mike, both pistons in every area measure the same except the skirt and there's no signs of any damage to the piston. I know this is primitive next to your standards but do you think I could run these with any confidence based on the info I got?
Thanks!
 
Looked at the numbers you posted and I see you are talking about a discrepancy of .0032. Even with a mike out of calibration you could see that difference between the parts using the same mike to measure the skirts at the gauge point. Feeler gauge method is what was done in the 50s, no offense meant.
But the issue is the cylinders are now true and straight (allegedly) and both bored and honed to their respective pistons. If you get a replacement you will need to adjust for that assuming there was no measuring errors or gauging problems.
The clearance is built into the piston and most manufacturers these days have their machining very close, shops that another story.
Put the rings in these bores and measure the gaps, that will tell a story too. If the bores were individually sized and are at .0013 and the holes are different size as stated the ring gaps will vary too. KBs ring gaps are about .016 out of the wrapper on the 95" pistons when proper sizing is done. Use the piston upside down to move them up and down the stroke and hold the barrels up to light, look for light passing the outside of the ring. If you find that anywhere look for a new machine shop and bring them the whole package to redo with equally sized pistons. I set up the KB at .001 and have done probably over 100 that way and they all work well assuming the ring gapping is done properly. I gap the top at .0028 and second at .0016
 
IF you use the pistons Now on this Build (I would) the company Knows you have a Maybe Problem and have offered you New pistons oversize. That might prove to still Not be an issue with them IF you develop piston slap in the Near future.

IF you ask the KB rep for you to Use the ones you have now and IF problems in the near future,,,, will they honor that replacement. Same amount of $$ for you to Re-bore and Hone and fit. Just your labor involved IF they go bad.

I like Don, think you'll have no problems with it. His suggestions and answers to your problem are good ones. Mine might be a little IF-E:p

signed....BUBBIE
 
One thing kind of nags at me about this situation..
Why didn't the shop call you before boring the cylinders instead of going ahead?
 
I was in the shop with him & knew what I was into. Be advised I'm in Thailand and only have 1 set of torque plates. We measured everything & agreed on clearance (another guy there tried telling me what clearance #'s I wanted). Scary to think what might happen if I wasn't there, but the guys actually pretty thorough & uses his dial bore gauge a lot.
As for checking ring gap & light through out the stroke I don't think I can give you an accurate answer just yet. Dropped off my torque plates to get copied so I don't have to change them between cylinders. Without them I'm getting no light anywhere (using 2nd compression ring) but ring gap variations of .003" & a tight .005". Both have the wider gaps in the middle of the barrel. The plates wont be done till next weekend, probably have different #'s then.
What's exceptable for gap variation through the stoke with torque plates attached?
Thanks!!
 
I've been in the machinist trade for about 25 years now and have done a bit of piston aircraft work at Lycoming in Pa many years ago. Been in the medical device business for about 15 of those 25 years now. I can't tell you for sure about these 2different pistons but, assuming reasonable feel on your micrometer, .003 + difference sounds like a LOT of difference to me. If those slugs are sold as a particularly sized set my humble opinion is either their QC or manufacturing process sucks or both. They hire guys off the street where I work that have NO experience at all and call them machinists! I wouldn't trust some of the jokers I work with to WASH my bike! And this is a worldwide known medical device manufacturer! MEDICAL DEVICES! I don't know much about sizing pistons to bores on a Harley except the absolute requirement to use torque plates but I can tell you this, I am currently doing a lot of CNC milling on 15+ year old machines and we can hold +/-
.0005 all day on MILLING a bore, no sweat. .003+ variance on a piston? Sounds to me like KB maybe outsourced to china or they are using no experience "machinists". For what it's worth, I wouldn't use them in my ride. Hope it works out for you either way!
 
DonDorfman said:
Can't disagree with anything you said but you missed the country of origin, Mexico:ap
Click to expand...

OOPS!

This is only partially related to this post but here goes anyways, you know the part that really jacks me up is the fact that the cheapness is not reflected in the price WE pay! My previous outsourcing medical device manufacturer of 18 years was my education. I learned a lot in my 18 years there and, contrary to their official "mission statement", patient care and quality is NOT job 1. Make it as cheap as possible, and extract the absolute maximum profit is the real unofficial mission statement! They managed to cut their labor costs to basically zero by outsourcing most of our most profitable machine work to the chinese but guess what? No change in the customer cost! Is it any wonder that when the surgeons started to notice the junk we were selling we started losing customers big time? As I predicted 10 years in advance, there was no stopping the suits from pursuing the free labor but eventually all of the work would come back and guess what? The multi million dollar factory that they built in china now sits empty! I love it! The only thing the suits really see is the bottom line, I vote as often as I can with my wallet! Moral of this rant? Find a privately owned piston manufacturer in the U.S.A. if possible and help THEM feed THEIR kids! Private equity investors make me want to do things I shouldn't even think about.I hope HD doesn't go any cheaper than they already have.
 
Screwylouie,
Cheap labor; seems that's what's it's all about worldwide these days.
Jack,
Cast flat tops. (348's)
The new .010" over pistons from UEM (Keith Black) arrived today. Everything measures even, at least with my tools. Getting my torque plates back tomorrow & I have another set of cylinders. I'm gona run with these if the bore/hone comes out mint. I might save the off set for a bike in the States where I'm close to parts & good machine shops. I'll post after some break in miles if anyones interested.
 
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