Standard bore piston ring set for the 3.250 inch Onan opposed twin. Replaces Onan 113-0310. FITS B43, B48 P216, P218, P220, P248 OL16, OL18, OL20 LX720, LX770, LX790 RING STACK Top compression - .058 inch Second compression - .058 inch Oil control - .125 inch, three piece ONE SET, ONE CYLINDER. These are opposed twin engines. A complete engine needs two sets. Order both before you take it apart. WHICH RING SET YOUR ENGINE NEEDS - GO BY THE PISTON. Onan used two ring groove thicknesses on this one bore, and it is the piston that decides, not the model or the year: Piston casting 112-0277 - .058 inch grooves - ring set 113-0310 - THIS SET Castings 112-0163 and 112-0246 - .077 inch grooves - ring set 113-0314 Because 112-0264 is the only piston Onan still supplies, an engine rebuilt at any point in the last few decades is likely to be on the .058 grooves regardless of when it was built. That is why the piston is the check and the model number is not. THE COIN TEST. A penny measures close to .058 inch. If a penny fits the top two grooves, this is your set. NOT THE BF. The BF is 3-1/8 inch bore. A BF that has been bored to 3-1/4 inch and fitted with the current piston does take this set, but a standard BF does not. OVERSIZES 113-0310-01 - .010 inch 113-0310-02 - .020 inch 113-0310-03 - .030 inch Replace both pistons as a pair. A mismatched pair runs out of balance.
- FITS THE 3.250 INCH BORE ONAN TWINS - B43, B48, P216, P218, P220, P248, OL16, OL18, OL20 and the LX720, LX770 and LX790. Replaces Onan 113-0310. Ring stack is .058 top, .058 second and a .125 three-piece oil control ring.
- ONE SET DOES ONE CYLINDER - These are opposed twins. A complete engine needs TWO sets. This is the single most common ordering mistake on this part, and it is worth getting right before you split the engine down rather than halfway through.
- THE CHECK IS YOUR PISTON, NOT YOUR MODEL YEAR - Onan used two ring thicknesses on this bore and the difference is the piston, not the engine's age. Piston casting 112-0277 has .058 inch grooves and takes this set. The earlier castings, 112-0163 and 112-0246, have .077 inch grooves and take 113-0314 instead. An engine rebuilt at any point in the last forty years may have either.
- THE COIN TEST - A penny is very close to .058 inch. If a penny slides into the top two ring grooves, this is your set. If the grooves are noticeably wider and a penny rattles, you need 113-0314. It is crude and it works, and it beats guessing from the model number.
- NOT THE BF, AND CHECK BEFORE YOU BUY OVERSIZE - The BF is a 3-1/8 inch bore engine and is not covered here, though a BF that has been bored out to 3-1/4 inch and fitted with the current piston does take this set. Oversizes are 113-0310-01 at .010, -02 at .020 and -03 at .030. Replace both pistons as a pair or the engine runs out of balance.