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Old 11-20-2020, 12:24 PM
  #48926  
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Originally Posted by Jesse Open View Post
Yes and otherwise was never implied.
Increased speeds place added burdens on oiling. I have never had a problem with 14% oil nor at times with 12% in large Saito engines. Very few hobbyists have the tools to properly determine the running clearances.

Good luck with the Horizon "warranty repairs"

If the crankpin has picked up any aluminum, the new rod may fail rather quickly. A lye cleanup could help.
What do you think the big end clearance should be?

Last edited by Glowgeek; 11-20-2020 at 12:53 PM.
Old 11-20-2020, 01:26 PM
  #48927  
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Increase clearance to 0.002"
Old 11-20-2020, 02:10 PM
  #48928  
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Originally Posted by modeltronics View Post
Gary
Tell me what I should look for to see if the crank pin picked up any aluminum. I cleaned the crank pin with Scotchbrite and I am going to put the crank in an ultrasonic cleaner. Since I don't' have the new rod yet I can do any additional steps that are needed while I wait.
Look first for streaks or patches that are brighter silver than the gray steel parent metal of the crankshaft. Clean up of minor patches can be done carefully with some dilute sodium hydroxide. (Lye, Draino, oven cleaner. Wear rubber gloves) Wet the pin and allow it to soak and scrub with the Scotchbrite. Wash well and oil the crank when done.

Also seen folks shave it off with an x-acto blade, I would still follow and finish with the etch.
Old 11-20-2020, 06:40 PM
  #48929  
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Originally Posted by Jesse Open View Post
Yes and otherwise was never implied.
Increased speeds place added burdens on oiling. I have never had a problem with 14% oil nor at times with 12% in large Saito engines. Very few hobbyists have the tools to properly determine the running clearances.

Good luck with the Horizon "warranty repairs"

If the crankpin has picked up any aluminum, the new rod may fail rather quickly. A lye cleanup could help.

Gary, what do you think the manufacturers do for the ID end fit on the rods ends ? maybe a reamer ?

Jim
Old 11-20-2020, 07:43 PM
  #48930  
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Never looked that hard. Either a dedicated reamer or, a better tool would be a broach. Reamers can be rather untrustworthy. Broaches are long life and very repeatable.

Those main bearing and rod bearing shells as well as insert cam bearings are usually sized with a broach, at least they were.
Old 11-20-2020, 07:52 PM
  #48931  
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Gary

I looked at the crank pin under magnification. I thought I could see little lines around the diameter. I tried a little oven cleaner that I use to clean the window on our wood burning stove on it. Then I scrubbed it with Scotchbrite. After a good water clean, I could feel little groves with my finger nail. They are very hard to see but I think I can feel them. Next, I pulled a similar looking crank shaft from my parts box. I think it was from a 56. Rubbing my finger nail on that crank pin felt much smoother. I looked up the part number for the crank on the 50 and 56 and found out it was the same part number. I am not going to put the original crank shaft back in the engine, I’m going to use the spare one I had.

Interesting side note… The threaded section of the replacement crank shaft is about inch longer than the original one that was in the engine.

Since the replacement crank shaft came from a bag of parts I bought at a swap meet, I did check the run out with a dial indicator. I have no idea of its history. It was good to go.

I think the oven cleaner trick saved me from using a crank shaft that may have caused a problem further down the line.

I now have the lower part of the engine assembled with new bearings. All I need is the new con rod to come in the mail.
Pedro
Old 11-20-2020, 08:15 PM
  #48932  
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If those ridges were raised, good chance they are aluminum .

Jim,

Back in the early 197Os there was a time when replacement valve guides for certain mot*****les were hard to buy. I had an old Logan lathe with a six position tailstock that I pulled from the trash at a local shop. With a little effort I tooled that lathe to make guides from cored 660 bronze bar stock. I wanted a smooth but hard bore in the guides. I wound up pushing chrome bearing balls thru the .002 undersized bore with an arbor press using castor oil as a burnishing lubricant. The bores were beautiful, on size and a work hardened surface. Kept me in business doing valve jobs on those Britbike heads for the local bike shops. Had enough left over to sell across the USA via mail order too. Ball burnishing would not work so well on rod bearings however
Old 11-21-2020, 02:44 AM
  #48933  
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Pedro, I've had some crank pins that felt like that both before and after cleaning/polishing. The worst one I found in a well used 56 about 3 years ago, had a few deep scratches in the pin and in the rod. Many gallons of fuel later it's still running fine at over 10k rpm with those same parts. The pin/rod clearance on that one measured a little over .003" using a mic and gauge pin set. I run 15% synth/2.5% castor. If I took it apart today I'm sure I would find that castor varnish has filled in the scratches.

Built up crud or aluminum on the crank pin could case issues but scratches aren't anything to worry about imo. Think of them as micro oil channels.
Old 11-21-2020, 06:50 AM
  #48934  
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Of course,

As long as they are light grooves, not raised ridges. And no aluminum in those grooves.Still, if you have a crank with a pristine journal, makes better sense to use the best one with that fresh rod.
Old 11-21-2020, 07:16 AM
  #48935  
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By all means, yes, gunk and ridges must be removed before putting a crank back into service!

That particular 56 crank pin had raised ridges adjacent to the scratches which I removed using the "shoe shine" method and emery cloth. Sand or any kind of hard foreign debris can cause those scratches. Easy for bad stuff to enter in through an unfiltered carb or unplumbed case vent. I do use tubing on vent nipples but no carb filter as we have a nicely groomed grass runway. If I flew off of a dirt or sandy runway I'd be using a carb filter and would install a tee fitting and additional tube in the vent line,capped for injecting ARO.

Last edited by Glowgeek; 11-21-2020 at 08:40 AM.
Old 11-21-2020, 08:12 AM
  #48936  
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In a pinch I guess.

I do prefer to avoid unbacked abrasive cloth in situations like this; At least for the bulk of metal removal
Careful use of hard oil stones is a very effective means to level the the high spots without removing metal elsewhere. There are shaped stones available that work well on a radius but with practice an arc motion with even a flat stone can do a fine job. The mission is to remove only the raised edges of the furrow.

Still better to simply start with an undamaged crank.Especially when you already have one.
Old 11-21-2020, 08:29 AM
  #48937  
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Proof's in the pudding Gary, the crank pin mic'd great, the engine runs great and it took less the 20 seconds to shoe shine the burrs off, all without the risk of accidently creating a flat spot on the pin trying to use a stone. It took longer to clean and polish the pin than it did to remove the burrs and I didn't have to be very careful, no need.
Old 11-21-2020, 09:05 AM
  #48938  
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Anecdotal,
I did not say it would not work or would not run . I offered a different method.
Sure, "It worked" yet overall not as precise and needlessly removes metal that could have been preserved.

Lonnie, not certain of your occupation, but I also "shoe polished" journals at one time as well, 50 years ago. Since then, working in the metals trades I have learned other methods. Using an oilstone slip takes little, if any more time and the results are far closer to my liking.

The work we did was subject to standards and inspection. A flat anvil micrometer only measures across the high spots. It ignores the low spots that the shoe polishing created.
I would love to shadowgraph that shoe polished surface before and after.


Bottom line remains : The new, undamaged crankpin already on hand is the way to go.


Last edited by Jesse Open; 11-21-2020 at 09:09 AM.
Old 11-21-2020, 09:20 AM
  #48939  
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This thread is like a box of chocolates, You never know what your going to get.
Old 11-21-2020, 09:26 AM
  #48940  
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Or why
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Old 11-21-2020, 09:40 AM
  #48941  
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Can't argue with that.

Or this: "Bottom line remains : The new, undamaged crankpin already on hand is the way to go."

Also, can't argue that a very fine abrasive slip stone in the hands of a talented operator would yield better results. I don't have the appropriate stone and I'm not a talented slip stone operator.

Run what ya brung!

Last edited by Glowgeek; 11-21-2020 at 10:04 AM.
Old 11-21-2020, 10:07 AM
  #48942  
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So many possible ways to use slip and stone and get banned.
Old 11-21-2020, 10:15 AM
  #48943  
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Originally Posted by acdii View Post
So many possible ways to use slip and stone and get banned.
Which reminds me. Did you ever get around to bending your pipe with your balls?
Old 11-21-2020, 12:13 PM
  #48944  
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Originally Posted by Glowgeek View Post
Which reminds me. Did you ever get around to bending your pipe with your balls?
I was wondering when that would show up again!
Old 11-21-2020, 12:35 PM
  #48945  
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Good to see you still have a sense of humor Mike, you've been through a lot lately. I hope your feeling better brother.
Old 11-21-2020, 12:50 PM
  #48946  
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If you can't laugh at life's little challenges you either drive yourself crazy or lay down and die. I'm already crazy enough, and I still have airplanes to build and fly with Saitos of course!
Old 11-21-2020, 01:54 PM
  #48947  
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Originally Posted by acdii View Post
So many possible ways to use slip and stone and get banned.

Just avoid real dirty stuff....


Like Motor***les
Old 11-21-2020, 03:51 PM
  #48948  
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Originally Posted by Glowgeek View Post
Which reminds me. Did you ever get around to bending your pipe with your balls?
Tried a test bend, was quite painful. I'll use a vise instead of my teeth next time. Actually still waiting on some tooling and the hex stock to arrive, supposed to be in at the end of the month.
Old 11-21-2020, 05:31 PM
  #48949  
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What size hex stock do you need?
Old 11-21-2020, 06:08 PM
  #48950  
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Originally Posted by Jesse Open View Post
Never looked that hard. Either a dedicated reamer or, a better tool would be a broach. Reamers can be rather untrustworthy. Broaches are long life and very repeatable.

Those main bearing and rod bearing shells as well as insert cam bearings are usually sized with a broach, at least they were.

thank you Gary !!

Jim

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