B&S 127CC 4-Stroke Screeching Noise

My dad and I recently dug our mini bike out of the shed and cleaned it up, it is a Sears Drover that we bought already modified.

The engine that was on it was a Briggs and Stratton 3HP engine(I didn't see the CCs but probably 127) it was shot, couldn't get it to run se we replaced the engine with one sitting around in my dads shop(A 127CC 3HP B&S). Before we replaced the first engine it would run for a few seconds then shut off, but when it ran it made a terrible screeching noise.

Long story short we got the new engine on and running, now sometimes when I hit a bump in the lawn or just at random the new engine makes the noise, it runs fine though. I turn the engine off and the noise stop, yet once the cord didn't respool correctly and another time it felt as if there was no compression.

What could be the problem? I don't know of it doesn't have enough oil making something scrape or if something in the recoil is at fault, or likely just age, both engines are older so. I can post pictures if that matters but I don't think it does.
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Well-Known Member
Your local napa (if you have one) will have a brand new four screw starter clutch hanging on the wall. Even if there in good shape i‘ll throw a two screw starter clutch in the garbage. I understand they are probably fine but if one screw vibrates out of the two screw clutch that is six ball bearings partying around and one screw holding the roof on...


Well-Known Member
I have to agree, it is most likely the starter clutch.

Unscrew the starter clutch assembly from the crankshaft extension. Open it up (pry the lid open with a flat screwdriver) and inspect the balls. Clean them if necessary but leave them dry, also clean the "star chamber" where the balls nestle. You don't have to go OCD on it and make it spotless, just make it clean and free of foreign debris.

However... clean both the inside of the starter clutch ratchet (the square piece) AND the extension of the crankshaft that the starter clutch ratchet fits on. If the starter clutch assembly is dirty or rusty that can cause screeching. A good way to clean the ratchet is with a .40-.45 caliber bore brush or just wrap cloth around a screwdriver and clean the interior. If the crankshaft extension is rusty or has dried gunk on it, clean it with a solvent and 600 grit (or finer grit) sandpaper, coarse steel wool, etc., until it is smooth and shiny and then lubricate it with oil. Use a few drops of clean motor oil and then reassemble it.

Another way to lubricate it is to assemble it dry and then look for the tiny hole on the end of the starter ratchet and, tilting the motor on its side, put several drops of oil into that hole. There is supposed to be a small felt disc behind the hole that is designed to retain oil and help lubricate the assembly, so make sure the felt is adequately saturated with oil. If the felt is missing, you can still apply a few drops of oil anyway. Some have suggested using ATF (automatic transmission fluid, the red kind) as a substitute.

Lastly -- Another possible reason for screeching: Make sure the blower cover/shroud isn't rubbing against the flywheel, that could also cause noise. It's just sheet metal and several good foot kicks, bumps or knocks against stumps, stones, etc. can knock it out of whack. On many mini bikes, the side of the engine with the blower cover on it hangs outside of the frame a little bit so it is vulnerable to damage.