Need some help, cylinder scoring

Have an old early 80s JD self propelled mower, perfect machine for me. Old original engine started making noise, using oil, then losing power. Tear down showed the aluminum bore scored up bad, piston in bad shape too. Replaced it last spring with a basic NOS shortblock. with new internal drive components, eliminated the points. Pretty much disaster. Ran it for 1- or 15 minutes and drained the oil, silver colored with aluminum flake. Ran it through the summer, 10 or 12 hours, 5 oil changes. Every change the oil was full of the same metal flake, silvery stuff. Ran fine to start with but at the end of summer the engine was smoking and using oil, losing power. Same result as the old block I'm no master mechanic but I have been wrenching on engines for a while, it was done right. Used Briggs&Stratton 30wt oil in the new motor, $20 worth for about 10 hours run time. So, is there a trick to getting these Kool Bore engines to live? Is the Briggs oil really right for these engines? I read the new oils are not what they used to be. I'm really just lost here.

IF you followed the correct O/H manual, AND the SPEC-sheets, I don't understand why this could be, BUT, crap happens, I think you may have to pull it back down, and probably (if not badly scored) CHECK bore DIAMETER, hone the cylinder, clean-up the piston, replace the rings, (being sure of gap locations) check rod & "bearings" and you might "skate" by.... or wind up replacing with a used similar better engine with a cast iron good sleeve. Keep us posted...........

I read the new oils are not what they used to be.

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Very true...they are much better now than in decades past.

I appreciate the quick replies. This was a new shortblock. Piston, rings, cylinder bore, rod, crank, valves, etc all new and factory installed. I'm really at a loss here. That old engine ran great for 35 years mowing lots more grass than here now, well maintained, then self destructed. New engine, same thing in one season. Hate to throw more money into this and get same result.

tom3 said:

I appreciate the quick replies. This was a new shortblock. Piston, rings, cylinder bore, rod, crank, valves, etc all new and factory installed. I'm really at a loss here. That old engine ran great for 35 years mowing lots more grass than here now, well maintained, then self destructed. New engine, same thing in one season. Hate to throw more money into this and get same result.

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Was there ANY type of warranty on the short block.. ?? You're sure it had full oil ..RIGHT ..?? I think I'd be on the "horn" with one of their rep's REAL QUICK ( nice & calm ) BUT NOT arse-kissing either ! They have a name to protect AND YOU, have a pretty big Forum ! .. get the idea ??

I am curious to what is the cause of failure on the short block. Possible one of the parts that got put on the new block has an issue that caused the old engine to fail. Oil not present in rings from factory, and basically created a dry start even though there was oil in the engine.

Only used part that was in contact with oil was the sump base and I sure cleaned it up. This engine has an internal clutch for the aux. PTO. New cam with drive parts, valve clearance was spot on, crank and cam end play was good, everything was sprayed down with brake cleaner. Did not pull the piston but it had some factory lube and I oiled the bore as I could. Might be on to something there? Found an I/C block on Ebay with the iron sleeve, time for round two I suppose. But those aluminum bore engines usually seem to really run a while. Just odd that the old and new both did this. You guys see any of this?

And thanks for the engine names and descriptions Boobala, that could come in handy.

Tom what is your model number ???? Also if you bought a shortblock you didn't have to put a sump cover on it, they come with one...

If you have the 12 series about a 6 HP I can help you get a SB for 75 BUX......

Let us know Mon Ami ~!~!

Boudreaux In Eunice La. said:

Tom what is your model number ???? Also if you bought a shortblock you didn't have to put a sump cover on it, they come with one...

If you have the 12 series about a 6 HP I can help you get a SB for 75 BUX......

Let us know Mon Ami ~!~!

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This was engine model 110985 4 HP vertical. Rebuild using a 398225 short block with a 396036 cam assy. (includes oil slinger, comp. release, torsion spring and clutch hub). Had to use original sump to have the clutch lever and shaft for the aux. PTO. Pretty rare engine I suspect with that internal drive clutch. Never seen this on anything but the old Deere SP mowers. Sure thought I'd have a mower that would last me till I'm done. Haven't given up yet though.

Did see a Snapper rear wheel drive with a Honda engine today at Wall Mart, reasonable price and includes all accessories, but plastic wheels, steel deck, and probably a gizmo rubber wheel deal drive mechanism. Hard to buy quality these days.

And that'd be a heck of a deal on that 12 cube shortblock for sure at $75.

Oooooh ok you got a aux drive on yours..... I love those....... A picture or a model number would have saved a lot confusion on my part......... LOL.....

Is your shaft out of the side of the engine with a sprocket ??

I just got 2 of of those 3.5 to 4 HP side shaft cam driven self propelled engines......

Those Snappers with the rubber tires are good quality...... I worked on one that was 12 years old not long ago.... It was a spring time tune up.... Tommy bought it new and paid 400 bux for it...

That drive system is the same as the Rear Engine riders that use to Snapperize your lawn many years ago on the ads on TV....