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318 B43G Engine Failure

1519 Views 4 Replies 3 Participants Last post by  jmiller1
I was wondering if anyone else has experienced the following failure on a Onan B43G engine.
While mowing (tractor did not hit anything) the engine destroyed a number of teeth on the crankshaft and camshaft gears. The oil pump looks alright with no damage. After engine disassembly I cannot find a cause of the failure. The crankshaft, rods, pistons, valves, springs and valve guides are all in great shape. The only failures were the gears. I hate to spend a lot of money fixing this and not know the cause. I have also included a picture of the case and assume the hole next to the crankshaft should be there it looks machined but I have nothing to compare it to.
Also will gears from an Onan P218 fit a B43G?

Any help would be appreciated
Thank you
John Miller

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Check your cam bearings, I have seen this before when the cam bearing either wears out or moves out of place allowing the cam to lift up.
Thanks Brad

I will check the bearing but it will be replaced as part of the rebuild.

John - I have experienced two cam gear failures on B43G engines. One failed without warning. This engine had worn cam bearings and the gears looked a lot like yours when it let go (~1800 hours). The other engine was torn apart before catastrophic failure. What sounded like rod knock was actually worn gears. This engine showed no other issues, other than worn gears (1200 hours).

I am pretty certain that gears from a P218 will work.

John Van
Thanks John for the response sounds like worn cam bearings is the cause of this failure.

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