OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Reel-Type Mowers SB 45 with Kirby / Lauson engine - How much oil?

Hi,

Hope someone can help me with a VERY basic question.

I have an old Scott Bonnar 45 with a Kirby / Lauson engine. (I think this is a H30A).

I understand that it takes 1.25 pints of oil. My conversion is that this is 700ml. Does this sound like the correct amount?

When I drained the old oil out it looked like there was only about 200ml in it! I guess it must have burnt/leaked a lot.

Many thanks from,
Henry

Hi RustyVicta, and a warm welcome to the forum.It' great to have another Scott Bonnar Model 45 owner on board.
We all like to learn new things and tinker here.
From what I have found through some research for you, 620 ml is mentioned.
But here on the engine(H4, but I would presume it would be the same for the H30) is the makers instructions:

Fill to overflow or to full mark if it has a dipstick.

Once again RustyVicta, to OutdoorKing.

Many thanks Darryl,

Thanks also for the very kind welcome to the forum.

I am thinking before I put the new oil in the mower I will flush it by adding around 500ml of Kero and leave it for 24hrs to disolve any crud that remained in the sump. I will then drain the kero and add the new oil.

Do you think this is a good idea?

Thanks from,
Henry

Hi Henry. I don't think that form of flushing will be terribly effective because it will not stir up the sludge, but if you drain the kerosene thoroughly it should do no harm. People who want to flush engines usually use a mixture of, say, 40% diesel with 60% clean engine oil, and start the engine and run it at idle with no load, for half a minute to a minute. Then they drain it immediately, tilting the engine steeply to maximise the amount of sludge that is expelled with the flushing agent. After thorough draining, fill with new engine oil and start the engine, running at idle only until it warms up completely. The objective is to protect the crankpin, which is the most vulnerable part of the engine when it comes to using inferior lubricants.

Flushing is a rather extreme process, and is definitely not something I would do to an engine unless it was considerably sludged up. However provided it is run slowly and briefly on a flushing agent that is more than 50% clean oil, it should do no harm. The objective then though, is to replace that mixture in the connecting rod bearing with pure oil without imposing much load on it in the meantime. Also, I suggest you never use any flushing technique on an OHV or OHC engine: those are 8:1 compression ratio, where the side valve engines are 6:1. The higher compression pressures impose far more load on the connecting rod's lower bearing.

Thanks Grumpy,

I really appreciate your advice.

Thanks from,
Henry.