Anybody messed with the chinese quads engines,,,,,

  My youngest Son bought a brand new 2 seater glorified Go Cart with a 7.5 HP engine that at first glance looks like a clone of a Briggs & Stratton  engine. It ran good for a few months but started out with electrical issues and I took it back to dealer in Craalsbad and he told me that his mechanic was not having any luck witht he danged electricla issues. He had 8 others in there with simmilar issues. He told me they were having to change out part by part til they got lucky and hit the part causing the NO START issue. I said thas OK if you take the new  part off for credit if that ain't the issue. He refused so I said I can do the same thing. I read several articles on youtube and finally found a guy that was selling a "KIT" that would do away with all the Bells & Whistles and just leave a push button start, and ON/OFF switch and thats it, no horn no lights no turn signals, no emergency flashers, no nuttin!!!! 

 It ran great for a couple of months abut now is hard to start.  After new spark plug and carb clean out, the sob will NOT start!!  Finally got my head out of my pocket and ran a compression check and compression is,,,,,30# Engine is OHV so I checked the valves thinking one was leaking open but no luck it just ain't got no compression! I was going to pull the cylinder to look at rings  but cylinder ID looks good!! On closer insppection ,,,the frigging cylinder is ONE PIECE with the crankcase, SO engine will havw to come out and engine opened all the way up so piston can be removed from crankshaft for possible broken ring,,,cylinder has NO RIDGE at top,,,,??

Anybody ever worked on one of these??

 Well CHIT,,,,but,,I figured as such,,altho, the cylinder is not scored or have any wear as per my calipers,,,,? The dealer guy told me these were clones of a Briggs & Stratton, but it having the cylinder built onto the block this must be the later version of the original clone. 

 Before I pull the engine out of frame, I'm gonna check the valves seating on head ,,,,? 

 You take aa red blooded American 7 year old boy,,,,and the Only'ist throttle position they know is "Pedal To The Metal" and still hunting for more,,,,,,

   Well,,as usual, ole Steve almost hits it on the head,,,I figured to atart at the easiest so I poured some gasoline on the combustion chamber and waited,,,and waited,,,and the friggin valves are not leaking thru,,,,!

  I figured to look at the rings and would go no farther. Took engine out of frame in bout 20 minutes and this block has an end plate that makes it plumb easy to remove the piston and rod and seen the problem right quick!!  The frigging rings are all STUCK!  Can't figure why,,,the cylinder nor the piston are not scored a bit,,,,SOOooo,,what happened for ALL the rings to get stuck???

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Ring grooves machined too narrow.

Worn lathe tool, missed replacement.

Carbon filled the gaps and grips the rings.

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As JVIN said- ring clearance in groove wasn't sufficient.

A fix?  pick the rings loose, pop out the pin and rod, CAREFULLY chuck the piston in lathe at the skirt (pad the jaws with strips of soft wood), and dial it in true... then skim a few thou out of the ring grooves with a SHARP HSS bit...

Another way would be to put valve grinding compound in the groove and work the rings, but that'll take a while... and risk getting grit embedded in the aluminum.

use a LATHE ????

dang, us reglar folks would use a fine hacksaw blade to make the grooves wider.....