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300421 ring gap?

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Guest
HELP.. working on a briggs 300421, does any one have the ring gap specs for this engine? just got the engine,looks good inside {may be too good} and the piston and bore look great. buttt.. when it gets hot it sounds like its locking up and is hard to turn by hand untill it cools. i suspect rings. also, does ring gap specs change for overbores? not sure if it's been bored out. can any one help?

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stevejj56
Charlie, Ring gap reject size for cast iron cylinders, .030 on compression rings and .035 on oil rings, the spects are the same for over bore. On the top of the piston is where its stamped .010 , .020 ,or .030 for over bore sizes, if it doesn't have this on it,it should be standard not counting wear. If its been bored the cylinder could be out of round or the piston to bore clearance is too tight. A good machine shop can check and correct this. Steven

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BenB
steven,thanks,pulled the piston out and found that i have a std bore, but some one used .010 or .020 over rings on a std. piston.thus =.001-.002 ring gap wayyyyy to tight .found in a couple of machine ref. books good rule of thumb is .003-.004 for each inch dia. of bore.so for a 3 1/4 apx. bore =.009-.012. i lightly filed ends to get to .011, will try to put together this weekend and hope for the best. i should have known it looked to good to be true,but still feel i got a good deal. B-12 complete , good shape,with engine,start/gen,lights[that still work] and no rips on o.e.m. seat for 140.00. worth that in spare parts for my 725's ,or visa versa. thanks again steven. charlie.

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stevejj56
Charlie, I hadn't seen the over size rings on a std. piston for a while so I didn't think of that. Heat expansion! It should work for you now. Some used to do that for a quick fix if they knew what they were doing. Have a great day, Steve

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