Topic: Loose is better than tight…. No sir it’s just loose

[CB750R]

I had a conversation with the machinist.

this guy missed his calling he should be selling snake oil… he pulled out his dial bore guage, mic’d a piston talked so much about how he only does high end engines, that he used to do work for several power sports placed.  (which is originally why I chose him) but he moved and talked so quickly as to not show me anything of substance with his dial bore gauge and micrometer.

In reality my cylinders were in my car over night it’s below freezing still, he didn’t actually show me anything aside that a .0020 feeler guage at the top of the bore is snug with the piston….

I came away convinced that he’s convinced he’s done no wrong.

I was able to buy a decent dial bore gauge and I did my own measurements.

Mike, has been a huge resource for me in this process so far, building me a wicked looking F2 head and has been advising and sourcing me parts to support my goal in building a great performing but still very streetable modified cb750. I really have appreciated all the efforts Mike has put in to help make this motor build happen so far and his offer to help get another set of cylinders machined to the proper specifications.

[willbird]

I used dial bore gauges in industry a lot for decades, all of ours read in .0001". I am amazed by how many folks building engines on youtube, actual full time shops with some fairly high end equipment are all using dial bore gauges that have a .001" indicator on them..they are guessing at the .0001". The better shops according to my rating have purchased a gauge ring in the sizes they use a lot rather than setting the dial bore gauge with a micrometer. In a production shop trying to check the gauge as often as you should using a micrometer is kind of a PITA, and training a person how to do that is tougher.

There is an axoim that your measuring tool should resolve to 1/10 of your total tolerance on the hole size.

I know it comes at a premium price but the CNC Rottler machine that fully automates the process of honing for size with diamond stones and then quickly putting plateau finish on with a finer diamond stone will net the best job IMHO. The older stuff CAN do a good job but it requires a LOT more operator input to get a result that is close to as good as the CNC Rottler result.

A friend of mine worked at a well known and respected shop in Toledo, OH a few years out of high school, he saw the guy ripping people off on engine balancing by just drilling a few existing holes in a crankshaft a bit deeper, he did not actually balance anything, it was for an AMC V8 which the shop owner thought was junk so not worthy of a real engine balance, but he was willing to CHARGE a guy for the work.

Bill

[grcamna2]

CB750R,I'm glad you have Mike working for you;I Know he does things to the proper specification 

[CB750R]

My bore gauge could use a better dial indicator atop it. But I think for identifying the uneven final bore dimensions I’m satisfied that I have been able to inspect it myself.

I’m really kicking myself in the ass. I do work in the Automotive aftermarket, and I do believe in buying local, and supporting businesses that support you. Unfortunately it has cost me time and money. Fortunately motorcycles are a hobby and it’s not a primary means of transport. Yes it’s a setback but it’s not keeping me from getting to and from my job.

I do realize there is a skill to using micrometers and bore gauges. I took my time and re produced the measurements several times before posting this.

[CB750R]

I just ran the bore gauge down a set of used stock cylinders I have. I’m getting less variation in bore dimensions on a used set of cylinders than I am with my “freshly ruined” cylinders.

That’s enough confirmation for me to trust my measurements and move forward.

[grcamna2]

I hope you leave a complete,informative online review for that machinist who did your job 'out of spec'.

[johno]

Looking at your bore measurements is classic barreling, less at top and bottom than in middle where the honer short strokes to get a pretty cross hatch pattern but doesn't measure the bore to check on his progress.  Common for backyard players but certainly not professional.

[HondaMan]

I had a conversation with the machinist.

this guy missed his calling he should be selling snake oil… he pulled out his dial bore guage, mic’d a piston talked so much about how he only does high end engines, that he used to do work for several power sports placed.  (which is originally why I chose him) but he moved and talked so quickly as to not show me anything of substance with his dial bore gauge and micrometer.

In reality my cylinders were in my car over night it’s below freezing still, he didn’t actually show me anything aside that a .0020 feeler guage at the top of the bore is snug with the piston….

I came away convinced that he’s convinced he’s done no wrong.

I wonder...did that guy used to live in Colorado, in a town called 'Englewood'?
It just sounds SO familiar...

[Don R]

 So, on a set of Wiseco 65mm pistons .0018" to .0025" is correct? I also read .0015 to .0018.
 I also have a set of NOS 64mm Wiseco from 1978 I assume the same clearance is OK?

[MRieck]

So, on a set of Wiseco 65mm pistons .0018" to .0025" is correct? I also read .0015 to .0018.
 I also have a set of NOS 64mm Wiseco from 1978 I assume the same clearance is OK?

Don...I'd run those old pistons around .002 and bore each cylinder to a specific piston.

[Don R]

So, on a set of Wiseco 65mm pistons .0018" to .0025" is correct? I also read .0015 to .0018.
 I also have a set of NOS 64mm Wiseco from 1978 I assume the same clearance is OK?

Don...I'd run those old pistons around .002 and bore each cylinder to a specific piston.

False alarm, my engine guy can't bore that small. He does pretty well at 4.610" though.

[NitroHunter]

False alarm, my engine guy can't bore that small. He does pretty well at 4.610" though.

Someone to keep in mind when you're ready to upsize to that 117mm REALLY big bore kit.

[Don R]

False alarm, my engine guy can't bore that small. He does pretty well at 4.610" though.

Someone to keep in mind when you're ready to upsize to that 117mm REALLY big bore kit.

  This guy fixed some stuff that no-one knew how to fix.

[CB750R]

Well my second set of cylinders is out to Millennium for boring. Have some fins to repair when it’s back, will see how that goes… but I’m more concerned with the internal function of this engine!

Should be a pretty punchy “750” when she’s back together.

[CB750R]

Aaaaand more fins got damaged in shipping…. Ffs I had that thing in a styrofoam cocoon…. In a cardboard cocoon, wrapped in lots of strapping tape…

Good thing I’m a function over form kinda guy.. however this stings a bit. Millennium says they can repair them.

[grcamna2]

Aaaaand more fins got damaged in shipping…. Ffs I had that thing in a styrofoam cocoon…. In a cardboard cocoon, wrapped in lots of strapping tape…

Good thing I’m a function over form kinda guy.. however this stings a bit. Millennium says they can repair them.

They were coming back to you from Millennium ?

[CB750R]

Aaaaand more fins got damaged in shipping…. Ffs I had that thing in a styrofoam cocoon…. In a cardboard cocoon, wrapped in lots of strapping tape…

Good thing I’m a function over form kinda guy.. however this stings a bit. Millennium says they can repair them.

They were coming back to you from Millennium ?

No just arrived at Millennium in that shape. Hope they make it home in one piece.

[PeWe]

Someone must have thrown something hard and heavy on the package.
A big sledgehammer?
Or it was dropped when unpacked?

A photo of the package at arrival could help to charge the shipping company if damaged during shipping.

[grcamna2]

I’ve joined the unfortunate club of motorcycle enthusiasts who have had their engines damaged by the good folks they pay lots of money to do their jobs!

My cylinders came back from the machinist, who I got to bore them out for the 65mm pistons. I showed him the paper and the clearances, and left the paper in the box with the pistons.

I decided to see how things looked and slid a piston in the bore and it was like sliding a hotdog through a culvert! Ok not that bad but I could rock the piston in the bore pretty easily. I have rebuild a couple dirtbikes and put pistons in a couple street bikes and had never seen a piston slide in so easily. I had another machinist measure up the bores and calculate the clearances. And I’ve attached his writing below.

I have a range of 0038-.0041” cylinder bore clearance when the sheet specifies .0025”

I’m pretty steamed about it, as this shop does some really high end work and shouldn’t be this sloppy. I’m working on a solution, but thank goodness I have enough experience to know that didn’t feel right otherwise I would’ve put together a noisy oil burning engine at best.

The title 'Loose is better than tight'  is that what the machinist told you ??  a quote ?   if so, I like your answer:  'No sir it's just loose'  which is exactly what any machinist should be told when they do this kind of thing.
I would have personally started this in 'the Pissed Off thread'.
Did the machinist finally own-up to his mistake ?

[CB750R]

I’ve joined the unfortunate club of motorcycle enthusiasts who have had their engines damaged by the good folks they pay lots of money to do their jobs!

My cylinders came back from the machinist, who I got to bore them out for the 65mm pistons. I showed him the paper and the clearances, and left the paper in the box with the pistons.

I decided to see how things looked and slid a piston in the bore and it was like sliding a hotdog through a culvert! Ok not that bad but I could rock the piston in the bore pretty easily. I have rebuild a couple dirtbikes and put pistons in a couple street bikes and had never seen a piston slide in so easily. I had another machinist measure up the bores and calculate the clearances. And I’ve attached his writing below.

I have a range of 0038-.0041” cylinder bore clearance when the sheet specifies .0025”

I’m pretty steamed about it, as this shop does some really high end work and shouldn’t be this sloppy. I’m working on a solution, but thank goodness I have enough experience to know that didn’t feel right otherwise I would’ve put together a noisy oil burning engine at best.

The title 'Loose is better than tight'  is that what the machinist told you ??  a quote ?   if so, I like your answer:  'No sir it's just loose'  which is exactly what any machinist should be told when they do this kind of thing.
I would have personally started this in 'the Pissed Off thread'.
Did the machinist finally own-up to his mistake ?

I’m in a bit of a No-win situation. He’s done a fine job of convincing himself that he’s done no wrong. His dog and pony show with me did prove he managed to machine the top inch of the bore to spec.. I was planning on comparing the second set of cylinders with my bore gauge with the first set and sending him the information when I can clearly show the barreling vs straight cylinders.

Unfortunately this guy is also a customer for the company I work for in sales, and it’s not my job to loose business. Sometimes being in the business has its disadvantages when it comes to getting personal work done. Then again being in the business means I talk to a lot of people…

[grcamna2]

I see..
A kind of a delicate situation.

[willbird]

Someone must have thrown something hard and heavy on the package.
A big sledgehammer?
Or it was dropped when unpacked?

A photo of the package at arrival could help to charge the shipping company if damaged during shipping.

Heard of of a situation where UPS lost a super rare set of airplane cylinders once, like $10k worth.

[grcamna2]

Well my second set of cylinders is out to Millennium for boring. Have some fins to repair when it’s back, will see how that goes… but I’m more concerned with the internal function of this engine!

Should be a pretty punchy “750” when she’s back together.

Will Millennium coat the cylinders and then bore to fit the orig. pistons you had brought to the first machinist ?

[CB750R]

So Cycle-x has a set of 65.5mm pistons on sale, anyone have experience with these? Would they be a solution for my loose barrels? I had been under the impression that 65mm was as big as stock sleeves should be pushed… millennium was actually a bit leery of going boring up for the 65mm pistons on the stock sleeves. 

This is only a question for salvaging the barrelled cylinders. I have another set for the $$$ engine build.

[grcamna2]

So Cycle-x has a set of 65.5mm pistons on sale, anyone have experience with these? Would they be a solution for my loose barrels? I had been under the impression that 65mm was as big as stock sleeves should be pushed… millennium was actually a bit leery of going boring up for the 65mm pistons on the stock sleeves. 

This is only a question for salvaging the barrelled cylinders. I have another set for the $$$ engine build.

How thick are your "barrelled" sleeves on the bottoms ?