861 Rebuild Pistons Bad

I have a 861 that I have been restoring. I bought a rebuild kit new sleeves pistons rings bearings, the works. Built the engine and it started and ran perfectly....for about 5 minutes. The engine started to lug and slow down as it warmed up and suddenly screeches to a sudden stop. You could immediately restart it and it would repeat this and screech to a stop.
I have a friend who happens to be a mechanical engineer, he advised to tear it back down and inspect everything....so I did. Damn.

Upon inspection all 4 pistons have scuffs on 4 sides of the piston skirts on all pistons. These scuffs are bad enough to transfer metal from the sleeves to the pistons. All this happen with less than 20 minutes total run time. Measuring the pistons and sleeves and comparing to the original 64 year old pistons and sleeves the new pistons have .022 clearance with the new sleeves. The original parts have .052 clearance.

I tell you all this
1. To warn others because this is too much work to do twice because of a parts issue.
2. to ask how good is YT in dealing with a warrantee `issue.

Steve Burnfin
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Wow, after all that work. I can only imagine how I would feel... I have only had one thing from YT that was built incorrectly and yes they immediately sent me another with no problem. The second Proofmeter I received was also made incorrectly. I disassembled the meter and calibrated it myself for the tractor I was working on. I did call back YT to let them know that the second one had the same problem and then described how it was made wrong and how to fix it. I hope YT contacted the manufacturer and held them accountable for the problem because without them giving feed back to the suppliers we will never fix all the parts that are "almost right". Steve good luck, I hope the repair goes smoothly. I am getting close to ordering parts for a rebuild and because of your post I will Mic. and double check everything before I install.
 
First thing the supplier will ask is did you hone the sleeves to size after pressing them in? Next question is were the wrist pins and bushings sized? Your machine shop is responsible for both.
 
What is the specification in the repair manual for piston to wall clearance? .022 sounds like a lot of clearance, where are you measuring and how?
 
I have a 861 that I have been restoring. I bought a rebuild kit new sleeves pistons rings bearings, the works. Built the engine and it started and ran perfectly....for about 5 minutes. The engine started to lug and slow down as it warmed up and suddenly screeches to a sudden stop. You could immediately restart it and it would repeat this and screech to a stop.
I have a friend who happens to be a mechanical engineer, he advised to tear it back down and inspect everything....so I did. Damn.

Upon inspection all 4 pistons have scuffs on 4 sides of the piston skirts on all pistons. These scuffs are bad enough to transfer metal from the sleeves to the pistons. All this happen with less than 20 minutes total run time. Measuring the pistons and sleeves and comparing to the original 64 year old pistons and sleeves the new pistons have .022 clearance with the new sleeves. The original parts have .052 clearance.

I tell you all this
1. To warn others because this is too much work to do twice because of a parts issue.
2. to ask how good is YT in dealing with a warrantee `issue.

Steve Burnfin View attachment 83747View attachment 83748View attachment 83749

I hate to say this but its up to you to find the issue if its a fit issue its not their problem. I assum .022 is the piston ring gap thats has little to do with piston skirt clearance.

Copy and paste

What is the standard piston clearance?


How much clearance is there between a piston and a cylinder ...


0.002 to 0.004 inch

It varies somewhat depending upon application, but generally speaking the gap between a piston and the cylinder within which it is fitted is in the order of 0.002 to 0.004 inch

It’s not uncommon for the clearance to not be correct out of the box. Its your job to find it and correct it.
 
I don't mean to pile on here, but what you found is just one of the reasons I don't do internal engine engine work any more. At one time the engine manufacturers supplied replacement parts you could rely on to fit properly. You could get by just spot checking fits and tolerances, plastic gauge a few bearings, and have pretty good success. Those days are long gone. Everything you buy now is suspect. Don't count on ANYTHING being the size it should be, or the quality/workmanship to be above suspicion. If you don't check and measure absolutely everything at least twice this is often the result you can expect. Obviously some supplier's products will be better than others, but nothing can be taken for granted any more.
 
I have a 861 that I have been restoring. I bought a rebuild kit new sleeves pistons rings bearings, the works. Built the engine and it started and ran perfectly....for about 5 minutes. The engine started to lug and slow down as it warmed up and suddenly screeches to a sudden stop. You could immediately restart it and it would repeat this and screech to a stop.
I have a friend who happens to be a mechanical engineer, he advised to tear it back down and inspect everything....so I did. Damn.

Upon inspection all 4 pistons have scuffs on 4 sides of the piston skirts on all pistons. These scuffs are bad enough to transfer metal from the sleeves to the pistons. All this happen with less than 20 minutes total run time. Measuring the pistons and sleeves and comparing to the original 64 year old pistons and sleeves the new pistons have .022 clearance with the new sleeves. The original parts have .052 clearance.

I tell you all this
1. To warn others because this is too much work to do twice because of a parts issue.
2. to ask how good is YT in dealing with a warrantee `issue.

Steve Burnfin View attachment 83747View attachment 83748View attachment 83749
No offense, but the fact that you're reporting to us piston clearances of .022 and .052" tells me that you either can't measure accurately, and/or you don't know where to measure. And, regardless of whether or not the pistons and sleeves were correctly sized to begin with, it's really incumbent upon you to check these clearances before final assembly. This is something I always do with parent bore and dry sleeve engines, but is not necessary on wet sleeve blocks. Since these are thin-wall dry sleeves, it doesn't take much to buckle them on installation, meaning I wouldn't be rushing to claim warranty. In other words, this problem may very well be your own fault.
 

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