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Discussion Starter #1
The 6.5 on my MTD pushmower has been rod knocking and smoking for 5 or 6 years . It was like this when I got it. I have thought about a new set of rings and looked in the manual but there is nothing in there about doing a topend. Do you hone them at all or just stick the rings in ? Do they respond to a new set of rings ? I was going to do a jury rig rod resize while I have it apart [ if possible ].

Thanks !!
 

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Any aluminum cylinder without a cast iron liner will have a coating of some hard material like Nikasil. These coatings have been used for years in motorcycles and are very durable. When changing piston and rings you never hone the cylinder. Sometimes you will see minor scratches usually caused because the air cleaner was compromised. Don't sweat them. Just keep the air cleaner as clean as possible. I realize this is hard to do on a lawnmower but it is the only way to get long life out of the cylinder.
 

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Briggs does not use Nikasil or any other coatings, that is motorcycle/atv technology. New rings in a worn engine is like putting a band-aid on a chest wound, the knock could be piston slap due to cylinder wear or a bad connecting rod. If you want tear it down and do some measuring but you are probably further ahead buying a new mower. Jerry rigging the rod will likely result in a hole in the block..
 

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Ray, unless you are married to it, replace it with a HF or a take-off from another mower. My opinion, worth exactly what I sell it for, is that aluminum-bored engines were a cost cutting 'feature' that proved not to be good for longevity. I think all the ones I've seen have been oil burners.
You can get a new HF Predator for $125:
https://www.harborfreight.com/55-hp-173cc-ohv-vertical-shaft-gas-engine-carb-69731.html
I think its retail would be less than the cost for new parts for the B&S. Sad to say, I don't think I'd put much into one with aluminum cylinder walls. If it is knocking, either it is worn out(likely some wear on the rod journal, cylinder tapered, ridged, and the main bearings(the aluminum of the casting, likely no bushing) have likely been oil starved now and again if it burns oil at all, or the cylinder wall/rings are gone.
I have nothing against them, and would have loved to have one when I pushed a reel mower as a kid, but would not put much into one unless I used it as a mini-'bush hog'.
tom
 

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Discussion Starter #5
I have been looking for a donor motor but end up with the wrong crank stub size. This is one of the MTD/Cub Cadet with the castering front wheels and I like the way it mows so I am wanting to stay with it. Should probably just look for a Cub version that has been sitting. I thought I had a new Honda motor found but after driving 45 mins to his location I discovered that there are adult men don't even have a tape measure much less know how to use it. He had a 25mm shaft and I need 7/8". PW motor so the crank was also not D&Ted. $60 would have been awesome.
 

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Discussion Starter #6
And the "jury rig rod resize" is 240 grit wet n dry on a plate glass and rub the mating surface of the rod to remove a few thou. Should work ok.

ETA, this is assuming there is no metal transfer between the rod and crank :tango_face_smile_bi
 

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Briggs does not use Nikasil or any other coatings, that is motorcycle/atv technology. New rings in a worn engine is like putting a band-aid on a chest wound, the knock could be piston slap due to cylinder wear or a bad connecting rod. If you want tear it down and do some measuring but you are probably further ahead buying a new mower. Jerry rigging the rod will likely result in a hole in the block..
No coating whatsoever??? An aluminum piston, steel rings in an aluminum cylinder how does that even work for 5 minutes in a clean environment let alone a dirty dusty lawn mower??? :tango_face_surprise:
 

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I'll look through the engines I got in the "Junk Windfall" and see if there's a 7/8 shaft motor. How long is the shaft below the mounting flange. I have a motor in the garage but it's also 25mm, don't guess you could another blade adapter. I'm to far to drive but I could send one to Lawrenceville next time my sister is home.
Cannon
 

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I had a dumpster mtd push mower that test ran on a shot of carb cleaner and ran long enough to feel vibration. I found star was stripped on blade adapter. I had a 7/8 but this engine was 25 mm. Mtd adapter was pricey so I bought an ayp and matching blade. Then I never got the mower running again. Turns out cylinder was too scored. If you get a good deal on an engine maybe it will come with adapter and then get blade to match or buy both to match engine.
 

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Have you considered the use of a sleeve to match the required diameter? Would another blade adapter work from a 'related' machine, such as the non-castering wheel versions? From what I gather, sleeves are readily available.
When I used a power mower back when, I found that front wheel driver models were much easier to use. I don't know if yours is self-propelled or not, but if you've never used a front wheel drive model, it might be a worthwhile thing to check.
tom
 

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No coating whatsoever??? An aluminum piston, steel rings in an aluminum cylinder how does that even work for 5 minutes in a clean environment let alone a dirty dusty lawn mower??? :tango_face_surprise:
It has worked very well for many years, there are millions out there. The piston is coated the cylinder is not.
 

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No coating whatsoever??? An aluminum piston, steel rings in an aluminum cylinder how does that even work for 5 minutes in a clean environment let alone a dirty dusty lawn mower??? :tango_face_surprise:
Oil, Grashopper. :fing32:
 
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