Onan B43, B48 & P216-P220 Rebuild Center
The Onan B43, B48, P216, P218 and P220 opposed twins all share a 3.250 inch standard bore, so many of their parts interchange. This page lists the engines it covers, the part numbers our parts replace, and the checks that sort out the parts that do not interchange.
At a glance
| Engines | B43, B43E, B43G, B43M · B48, B48G, B48M · BG, BGA, BGD, BGE, BGM · P216, P218, P220 (G and V) · P248 Later versions of the same engines: OL16, OL18, OL20 · LX720, LX770, LX790 |
|---|---|
| Standard bore | 3.250 in (82.55mm) on every engine above |
| Displacement | B43 and P216: 43 cu in · B48, P218 and P220: 47.7 cu in. Stroke is the difference, not bore. |
| Pistons | Standard: replaces 112-0264 Oversize: 0112-0264-10, 0112-0264-20, 0112-0264-30 |
| Ring sets | Late style, .058 in (1.5mm) grooves, piston casting 112-0277: 113-0310 Early style, .078 in (2.0mm) grooves, castings 112-0163 or 112-0246: 113-0314 (earlier 113-0189, 113-0186) |
| Connecting rods | 16 HP (B43, B43G, BF, P216, OL16, LX720): 114-0394 (earlier 114-0225, 114-0300) 18 to 20 HP (B48, BG, P218, P220, OL18, OL20, LX770, LX790): 114-0397 (earlier 114-0257) |
| Gaskets | Engine gasket set 168-0187 · head gasket 110-3181 (9 bolt) · oil filter adapter gasket 120-0771 |
| Valves | P series, OL and LX: intake 110-3479, exhaust 110-3480 B series: intake 110-2368 (earlier 110-1808), exhaust 110-1955 |
| P series valve train | Intake valve seal 509-0289 (replaces 509-0210) · guides 110-3526 intake, 110-3527 exhaust · springs 110-3485 · seats 110-0197 intake, 110-1824 exhaust · governor spring 150-1214 |
| Oversizes we carry | .010 (3.260 in) · .020 (3.270 in) · .030 (3.280 in) |
Check these five things before you order
- Model and spec number. They're on the nameplate on the engine, not the tag on the machine. The P220G-OHV is a different engine. If the valves are in the head rather than the block, this page is not for your engine. Where to find the tag
- Head bolt count. Nine bolts per head is this family. Ten bolts per head is the larger P224, T260 and NH family on a 3-9/16 inch bore, which takes different parts.
- Bore size. If the engine has been rebuilt before, it may already be .010, .020 or .030 oversize. Measure the bore or check the top of the old piston for a stamp.
- Ring groove (ring-only orders). Measure the top ring groove on your piston: 1.5mm (.058 in) takes 113-0310, 2.0mm (.078 in) takes 113-0314. A penny fits the narrow grooves and a nickel fits the wide ones. A piston-and-ring kit comes matched, so you can skip this one.
- Connecting rods. The 16 HP and 18 to 20 HP rods are different parts. The B43G is rated 18 HP but takes the 16 HP rod. Old-style rods have a hole cast through the beam. If yours are old style, replace both so the engine stays in balance.
Which kit do I need?
- Full rebuild, bore is good: the standard rebuild kit (two pistons, rings, gasket set and crank seals). For the B43, B48, BF and BG, the overhaul kit that adds intake and exhaust valves. Its valves do not fit the P series.
- Rings and reseal: the ring and gasket kit, late style 113-0310 or early style 113-0314.
- Rings only: a 113-0310 or 113-0314 ring set, or a .010 oversize late-style set. One set does one cylinder, so order two for a full engine.
- Cylinders bored oversize: .010, .020 or .030 pistons with rings, single or pair, or the .010, .020 or .030 rebuild kits with gaskets and seals. For the B43 and B48 there are also oversize kits that add valves.
- Connecting rods: 114-0394 or 114-0397, single or pair, matched to your horsepower and rod style.
- Valve work on the P series: intake and exhaust valves, guides, springs, seats and intake valve seals.
- Gaskets only: the full gasket set with seals, a head gasket pair, or the oil filter adapter gasket.
- Ignition: points and condenser for B43 and B48 engines with a single screw on the point cover.
More detail on measuring bores and matching rings: Measure before ordering rings and pistons.